This document presents a study characterizing active galactic nuclei (AGN) selected using mid-infrared colors from the Wide-field Infrared Survey Explorer (WISE). The authors find that a simple color criterion of W1-W2 ≥ 0.8 selects AGN with high reliability to a depth of W2 ∼ 15.0, identifying over 60 AGN candidates per square degree. This WISE selection method is effective at identifying both obscured and unobscured AGN. Using deep data in the COSMOS field, the authors explore the properties and redshift distribution of WISE-selected AGN candidates, finding the selection identifies 78% of AGN identified by previous Spitzer studies.
Chandra deep observation_of_xdcpj004402033_a_massive_galaxy_cluster_at_z_1_5Sérgio Sacani
Artigo apresenta os resultados obtidos pelo Chandra ao medir com precisão a massa do mais massivo aglomerado de galáxias do universo distante, o Aglomerado Gioiello.
This document summarizes an X-ray study of the supernova remnant G352.7-0.1 using data from XMM-Newton and Chandra observations. Prior observations revealed G352.7-0.1 has a shell-like radio morphology but center-filled thermal X-ray morphology, classifying it as a mixed-morphology supernova remnant. The new observations confirm the X-ray emission comes from the interior and is dominated by ejecta. Spectra from XMM-Newton are fit by a single thermal component with enhanced silicon and sulfur. Some Chandra spectra require a second thermal component to fit, with solar abundances providing a better physical model. No evidence of overionization was found. A neutron
1. The spectrum of the bright Kuiper Belt object 2005 FY9 is dominated by methane absorption features in the near-infrared region. However, the methane absorption lines are significantly broader than seen on any other solar system body, indicating unusually long optical path lengths through methane grains on 2005 FY9, estimated to be around 1 cm in size.
2. In addition to methane, the spectrum also shows clear evidence for ethane, which is expected to form from UV photolysis of methane. No evidence is found for nitrogen or carbon monoxide, both known to be present on Pluto.
3. The differences between 2005 FY9's spectrum and those of Pluto and 2003 UB313 are suggested
A spectroscopic redshift_measurement_for_a_luminous_lyman_break_galaxy_at_z _...Sérgio Sacani
This document presents the spectroscopic confirmation of a luminous Lyman break galaxy (LBG) at a redshift of z = 7.7302 ± 0.0006, as observed using the MOSFIRE instrument on the Keck I telescope. The galaxy, named EGS-zs8-1, was pre-selected as a promising candidate for spectroscopic follow-up based on its bright apparent magnitude of H = 25.0 and very red Spitzer/IRAC colors suggestive of strong emission lines. Spectroscopic observations revealed a clear detection of the Lyman-alpha emission line at a observed wavelength of 1.06 microns, reliably confirming the high photometric redshift of z~7.7. Analysis of the
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
The gravity field_and_interior_structure_of_enceladusSérgio Sacani
The gravity field and interior structure of Enceladus were determined using Doppler data from three Cassini flybys. There is a negative mass anomaly in the south polar region, largely compensated by a positive subsurface anomaly consistent with a regional subsurface sea at depths of 30-40 km extending to 50° south latitude. Enceladus deviates mildly from hydrostatic equilibrium, with estimated quadrupole coefficients indicating a differentiated body with a low-density core.
A mathematical algorithm was developed to calculate effective density values within Apollo lunar core samples using digitized radiographs. Code was written in MATLAB to produce density maps based on the algorithm. Factors like varying X-ray intensities due to the Inverse Square Law and different material thicknesses were accounted for. The resulting density maps provide reasonable values compared to previously measured bulk densities, but more information is needed to address issues in radiography and the physical parameters of the X-ray setup. With this additional information, density values as a function of depth and porosity can be accurately evaluated.
The muse 3_d_view_of_the_hubble_deep_field_southSérgio Sacani
Artigo mostra como foram as observações feitas com o MUSE, o novo instrumento do VLT do campo profundo do Hubble. Além de descobrir 20 novos objetos, o MUSE conseguiu medir as propriedades das galáxias e até representar as mais próximas em 3 dimensões.
Chandra deep observation_of_xdcpj004402033_a_massive_galaxy_cluster_at_z_1_5Sérgio Sacani
Artigo apresenta os resultados obtidos pelo Chandra ao medir com precisão a massa do mais massivo aglomerado de galáxias do universo distante, o Aglomerado Gioiello.
This document summarizes an X-ray study of the supernova remnant G352.7-0.1 using data from XMM-Newton and Chandra observations. Prior observations revealed G352.7-0.1 has a shell-like radio morphology but center-filled thermal X-ray morphology, classifying it as a mixed-morphology supernova remnant. The new observations confirm the X-ray emission comes from the interior and is dominated by ejecta. Spectra from XMM-Newton are fit by a single thermal component with enhanced silicon and sulfur. Some Chandra spectra require a second thermal component to fit, with solar abundances providing a better physical model. No evidence of overionization was found. A neutron
1. The spectrum of the bright Kuiper Belt object 2005 FY9 is dominated by methane absorption features in the near-infrared region. However, the methane absorption lines are significantly broader than seen on any other solar system body, indicating unusually long optical path lengths through methane grains on 2005 FY9, estimated to be around 1 cm in size.
2. In addition to methane, the spectrum also shows clear evidence for ethane, which is expected to form from UV photolysis of methane. No evidence is found for nitrogen or carbon monoxide, both known to be present on Pluto.
3. The differences between 2005 FY9's spectrum and those of Pluto and 2003 UB313 are suggested
A spectroscopic redshift_measurement_for_a_luminous_lyman_break_galaxy_at_z _...Sérgio Sacani
This document presents the spectroscopic confirmation of a luminous Lyman break galaxy (LBG) at a redshift of z = 7.7302 ± 0.0006, as observed using the MOSFIRE instrument on the Keck I telescope. The galaxy, named EGS-zs8-1, was pre-selected as a promising candidate for spectroscopic follow-up based on its bright apparent magnitude of H = 25.0 and very red Spitzer/IRAC colors suggestive of strong emission lines. Spectroscopic observations revealed a clear detection of the Lyman-alpha emission line at a observed wavelength of 1.06 microns, reliably confirming the high photometric redshift of z~7.7. Analysis of the
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
The gravity field_and_interior_structure_of_enceladusSérgio Sacani
The gravity field and interior structure of Enceladus were determined using Doppler data from three Cassini flybys. There is a negative mass anomaly in the south polar region, largely compensated by a positive subsurface anomaly consistent with a regional subsurface sea at depths of 30-40 km extending to 50° south latitude. Enceladus deviates mildly from hydrostatic equilibrium, with estimated quadrupole coefficients indicating a differentiated body with a low-density core.
A mathematical algorithm was developed to calculate effective density values within Apollo lunar core samples using digitized radiographs. Code was written in MATLAB to produce density maps based on the algorithm. Factors like varying X-ray intensities due to the Inverse Square Law and different material thicknesses were accounted for. The resulting density maps provide reasonable values compared to previously measured bulk densities, but more information is needed to address issues in radiography and the physical parameters of the X-ray setup. With this additional information, density values as a function of depth and porosity can be accurately evaluated.
The muse 3_d_view_of_the_hubble_deep_field_southSérgio Sacani
Artigo mostra como foram as observações feitas com o MUSE, o novo instrumento do VLT do campo profundo do Hubble. Além de descobrir 20 novos objetos, o MUSE conseguiu medir as propriedades das galáxias e até representar as mais próximas em 3 dimensões.
This document summarizes the results of infrared transmission spectroscopy of the exoplanets HD 209458b and XO-1b using the Hubble Space Telescope's Wide Field Camera 3 instrument. Key findings include:
- Both planets exhibited water absorption of approximately 200 ppm at the peak water absorption wavelength of 1.38 microns.
- The water absorption measured for XO-1b contradicts stronger absorption reported from previous observations using a different instrument.
- The weak water absorption measured for HD 209458b is consistent with previous observations of weak molecular absorption features for this planet.
- Model atmospheres including uniformly distributed extra opacity can approximately account for the water measurements as well as previous sodium absorption measurements for
This document summarizes a 1.3 mm continuum survey of protoplanetary disks in the 2-3 Myr old IC348 star cluster using the Submillimeter Array. 10 disks out of 85 young stars were detected with masses ranging from 2-6 Jupiter masses. This distribution is shifted to lower masses by a factor of 20 compared to younger regions like Taurus and Ophiuchus. The results reveal a rapid decline in the number of small dust grains in disks after 1 Myr, likely due to grain growth. The few detected disks may be the best candidates in IC348 to study planet formation.
A population of_fast_radio_bursts_ar_cosmological_distancesSérgio Sacani
1) Four fast radio bursts (FRBs) lasting only a few milliseconds were detected in a radio survey of the high Galactic latitude sky.
2) The bursts' properties indicate they are of celestial rather than terrestrial origin and likely originate from cosmological distances of 0.5 to 3 billion light years.
3) No coincident x-ray or gamma-ray signals were found associated with the bursts. Characterizing the population of FRBs could help determine the baryonic content of the universe.
Strategies for reducing the risk of radiation for astronauts in space mission...SMJ Mortazavi
Exposure to high levels of space radiation and microgravity are two important concerns which need to be addressed before any long-term manned space mission. There are also reports showing that microgravity, through a synergistic effect, increases the radiation susceptibility of living organisms. Other researchers as well as our team have conducted some experiments on design and fabrication of appropriate radiation shields for spacecrafts. However, due to some cardinal barriers such as weight limitations and extreme inadequacy of current physical shields during extravehicular activity, we strongly believe that the physical shielding alone cannot solve the problem of potential exposure to high levels of radiation in a long-term space mission.
Therefore, over the past several years, we focused on two solutions; radioadaptive response and other biological-based radiation protection methods. Adaptive response, that is the increased radioresistance in cells or living organisms pre-exposed to a low adapting dose and then exposed to a high challenging dose, was firstly proposed by our team in 2003 as an effective method. This novel idea later formed the basis of many space radiation biology projects around the world.
Furthermore, conventional radioprotectors cannot efficiently be used in space due to limitations such as their considerable toxicity and the very narrow time window for their effective use (radioprotectors should be used before or at the time of exposure, while astronauts cannot estimate their doses before a solar particle event). Therefore, we focused on introducing natural radiation mitigators which could be efficiently used several hours after exposure (e.g. when a solar particle event subsides and astronauts are able to estimate their doses). In these experiments, radiation mitigators were introduced by our team which could be used even 24 hours after exposure to high levels of radiation caused by unpredictable sources such as SPEs.
Finally, some of our recent experiments were aimed at finding methods which could lead to boosting the immune system of astronauts during long-term missions. We investigated the effect of RF-EMFs-induced adaptive responses on immune system modulation in a mouse model of hindlimb unloading (HU). Hindlimb unloading rodent model is widely accepted by the scientific community as the model of choice for simulating spaceflight. In this study, serum levels of T helper cytokines were determined in HU mice, RF-EMF treated mice and HU mice pre-exposed to RF-EMF compared to those of untreated controls. The findings of this study will be published soon.
Assessment of Activity Concentration of The Naturally Occurring Radioactive M...IOSR Journals
The activity concentrations of potassium, Radium and thorium in soil samples from a mining site in yankandutse, Kaduna north western Nigeria were measured using gamma ray spectroscopy method. Activity concentration of potassium, Radium and thorium were determined. The activity concentrations of 40K, 226Ra and 232Th, respectively in Bq kg-1 in the soil samples ranged as follows: K-40 196.11±2.02 to 553.03±1.08 with average of 382.01, Ra-226 .1506±.03 to 5.67±.03 with average of 2.08 and Th-232 18.13±3.19 to 73.09±1.59 with average activity concentrations of 47.23 .The mean activity concentration of potassium and radium are below average but for thorium the activity concentration is above average.
- Comet C/2011 N3 (SOHO) was observed by the Solar Dynamics Observatory as it passed through the low solar corona in July 2011.
- The comet survived within the corona until it came within 0.146 solar radii (approximately 100,000 km) of the solar surface, at which point its extreme ultraviolet signal disappeared.
- Before being destroyed, material released from the comet was first seen in absorption against the solar corona, then formed an emission nebula as it interacted with the coronal plasma.
1) This document describes an ALMA survey of 126 submillimeter galaxies (SMGs) previously detected in the LABOCA ECDFS Submillimeter Survey (LESS).
2) The ALMA observations resolve the SMGs with an angular resolution of ∼1.6", doubling the number of interferometrically observed SMGs.
3) Preliminary results find that at least 35-50% of the LESS sources have been resolved into multiple SMGs, with the average number increasing with LESS flux density.
The document summarizes various methods for detecting water hazards outdoors, including:
- Color imagery, which identifies water by its reflections but struggles with still water.
- Short wave infrared imagery, which detects water's dark appearance in infrared. However, performance degrades where water reflects vegetation or clouds.
- Thermal infrared imagery, where water appears cooler than terrain by day and warmer at night, but only detects the top water layer.
- Laser range finders can detect water through specular reflection but are limited by range and angle of incidence.
- Multi-feature methods combine cues like brightness, texture and range but require significant computation.
- Polarization imaging exploits water's polarized light reflection
This document presents aluminum abundances for about 100 red giant stars in each of the Galactic globular clusters 47 Tuc and M 4. The abundances were derived from intermediate-resolution FLAMES/GIRAFFE spectra, focusing on the Al I doublet at 8772-8773 Å. Previous homogeneous abundances of O, Na, Mg, and Si were also analyzed to study multiple stellar populations in these clusters. The data confirm two stellar populations are visible in M 4, while 47 Tuc shows evidence of at least three distinct stellar groups based on the abundances of O, Na, Mg, Al, and N.
This document presents observations of ACT-CL J0102−4915, a massive galaxy cluster discovered by the Atacama Cosmology Telescope (ACT) via its strong Sunyaev-Zeldovich signal. Optical and X-ray observations reveal that it is undergoing a major merger between components with a mass ratio of 2:1 at a redshift of 0.87. Chandra X-ray data show significant temperature variations across the cluster from 6.6 keV to 22 keV, indicating a hot, luminous system undergoing a merger. The cluster appears to be an excellent example of a "bullet cluster" system at high redshift.
Improved two-photon imaging of living neurons in brain tissue through tempora...julian choy
This document describes a study that optimized two-photon imaging of living neurons in brain tissue by temporally gating the incident laser to reduce photon flux while maximizing fluorescence signal. The study found that gating the laser at the sampling frequency compromised cell viability despite high fluorescence. An optimum gating frequency range was identified that maintained cell viability while preserving fluorescence levels in two-photon images. Cell viability was monitored by measuring changes in membrane input resistance during whole-cell patch recording of neurons.
This document discusses a new design of plasmonic nanoantenna with a slant gap that can enhance optical chirality. The slant gap provides an enhanced electric field parallel to an external magnetic field with a phase delay of π/2, resulting in enhanced optical chirality in the near field. Numerical simulations show this nanoantenna design can generate a near field with enhanced optical chirality when excited by linearly polarized light. This enhanced optical chirality could allow for circular dichroism analysis using linearly polarized light and may find applications in analyzing the chirality of surface-bound matter.
How does biological protection help astronauts tolerate high levels of radiationSMJ Mortazavi
Abstract:
Exposure to high levels of space radiation and microgravity are two important concerns which need to be addressed before any long-term manned space mission. There are also reports showing that microgravity, through a synergistic effect, increases the radiation susceptibility of living organisms. Other researchers as well as our team have conducted some experiments on design and fabrication of appropriate radiation shields for spacecrafts. However, due to some cardinal barriers such as weight limitations and extreme inadequacy of current physical shields during extravehicular activity, we strongly believe that the physical shielding alone cannot solve the problem of potential exposure to high levels of radiation in a long-term space mission.
Therefore, over the past several years, we focused on two solutions; radioadaptive response and other biological-based radiation protection methods. Adaptive response, that is the increased radioresistance in cells or living organisms pre-exposed to a low adapting dose and then exposed to a high challenging dose, was firstly proposed by our team in 2003 as an effective method. This novel idea later formed the basis of many space radiation biology projects around the world.
Furthermore, conventional radioprotectors cannot efficiently be used in space due to limitations such as their considerable toxicity and the very narrow time window for their effective use (radioprotectors should be used before or at the time of exposure, while astronauts cannot estimate their doses before a solar particle event). Therefore, we focused on introducing natural radiation mitigators which could be efficiently used several hours after exposure (e.g. when a solar particle event subsides and astronauts are able to estimate their doses). In these experiments, radiation mitigators were introduced by our team which could be used even 24 hours after exposure to high levels of radiation caused by unpredictable sources such as SPEs.
Finally, some of our recent experiments were aimed at finding methods which could lead to boosting the immune system of astronauts during long-term missions. We investigated the effect of RF-EMFs-induced adaptive responses on immune system modulation in a mouse model of hindlimb unloading (HU). Hindlimb unloading rodent model is widely accepted by the scientific community as the model of choice for simulating spaceflight. In this study, serum levels of T helper cytokines were determined in HU mice, RF-EMF treated mice and HU mice pre-exposed to RF-EMF compared to those of untreated controls. The findings of this study will be published soon.
This document provides an overview of the basics of remote sensing. It defines remote sensing as acquiring information about an object without direct contact. It discusses key components of the remote sensing process including data acquisition, the electromagnetic spectrum, atmospheric interactions, spectral signatures, and satellite platforms and orbits. Remote sensing draws from many areas and plays an important role in monitoring the Earth through satellite imagery.
WE1.L10 - INTERANNUAL VARIABILITY IN CLIMATE PRODUCTS FROM THE ATMOSPHERIC IN...grssieee
The document summarizes the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite. AIRS measures atmospheric temperature and humidity profiles as well as greenhouse gases. It has provided over 8 years of global observations used to improve weather forecasts and validate climate models. AIRS data has also enabled over 350 research publications studying topics like tropical cyclones, the Madden-Julian oscillation, and trends in outgoing longwave radiation.
Wei Li has published extensively in international scientific journals and books as well as international conference proceedings. Some of his notable publications include papers on spectral characterization of monolithic mode-locked lasers, superluminescent diodes at 1.55 μm, characterization of 1550 nm Fabry-Perot laser structures, and invited chapters in books on dilute nitride semiconductors and GaInNAs quantum well lasers. He has also published work on extending the emission wavelength of GaInNAs/GaAs quantum well lasers beyond 1300 nm and high performance 1.32 μm GaInNAs/GaAs single-quantum-well lasers.
This document summarizes a study on errors in particle tracking microrheology. It separates errors into static errors from position measurements of immobilized particles due to limited spatial resolution, and dynamic errors from particle motion during the finite exposure time required for visualization. The authors develop models to calculate how these errors propagate to measurements of mean-squared displacement. They verify the models using simulations and experiments on viscous fluids, showing static errors can be corrected using static experiments at similar noise levels. This increases accuracy for microrheology studies.
Geoffroy Lerosey has published extensively in peer-reviewed journals, with over 35 publications. His work focuses on manipulating waves and controlling propagation at subwavelength scales using techniques like time reversal and metamaterials. Some of his publications have been highlighted in prominent journals and received significant attention.
This document summarizes Hubble Space Telescope ultraviolet spectroscopy of four white dwarfs known to accrete planetary debris. The spectra reveal absorption lines from a variety of metals including carbon, oxygen, aluminum, silicon, phosphorus, sulfur, chromium, iron, and nickel. Combined with optical data, between five and eleven different metals are detected in each white dwarf, indicating substantial chemical diversity in the accreted planetary debris. The abundances observed provide insights into the composition and origin of the debris, with some debris resembling bulk Earth composition and others showing evidence of melting and differentiation.
1) Observations of a Lyman-alpha nebula (LAB1) reveal that the Lyman-alpha emission is polarized, with a polarization fraction of around 20% at radii of 45 kpc from the center.
2) The detection of polarized radiation indicates that the Lyman-alpha photons were produced in the galaxies within the nebula and scattered by neutral hydrogen at large distances, rather than being produced in situ.
3) The polarization vectors are oriented tangentially to the overall geometry of the nebula, consistent with theoretical expectations for Lyman-alpha photons produced centrally and scattered at large radii.
1) The document presents new observations of shell structures in the halo of galaxy NGC 7600 and a movie from a cosmological simulation showing how shell galaxies can form in a cold dark matter universe.
2) The movie illustrates how the continuous accretion of dark matter and star clumps creates diffuse circumgalactic structures, and how the disruption of a massive clump on a near-radial orbit creates a complex system of concentric shells resembling those of NGC 7600.
3) With the aid of the simulation, the authors interpret NGC 7600 in the context of the cold dark matter model of galaxy formation through the accretion and disruption of smaller companion galaxies.
This document summarizes the results of infrared transmission spectroscopy of the exoplanets HD 209458b and XO-1b using the Hubble Space Telescope's Wide Field Camera 3 instrument. Key findings include:
- Both planets exhibited water absorption of approximately 200 ppm at the peak water absorption wavelength of 1.38 microns.
- The water absorption measured for XO-1b contradicts stronger absorption reported from previous observations using a different instrument.
- The weak water absorption measured for HD 209458b is consistent with previous observations of weak molecular absorption features for this planet.
- Model atmospheres including uniformly distributed extra opacity can approximately account for the water measurements as well as previous sodium absorption measurements for
This document summarizes a 1.3 mm continuum survey of protoplanetary disks in the 2-3 Myr old IC348 star cluster using the Submillimeter Array. 10 disks out of 85 young stars were detected with masses ranging from 2-6 Jupiter masses. This distribution is shifted to lower masses by a factor of 20 compared to younger regions like Taurus and Ophiuchus. The results reveal a rapid decline in the number of small dust grains in disks after 1 Myr, likely due to grain growth. The few detected disks may be the best candidates in IC348 to study planet formation.
A population of_fast_radio_bursts_ar_cosmological_distancesSérgio Sacani
1) Four fast radio bursts (FRBs) lasting only a few milliseconds were detected in a radio survey of the high Galactic latitude sky.
2) The bursts' properties indicate they are of celestial rather than terrestrial origin and likely originate from cosmological distances of 0.5 to 3 billion light years.
3) No coincident x-ray or gamma-ray signals were found associated with the bursts. Characterizing the population of FRBs could help determine the baryonic content of the universe.
Strategies for reducing the risk of radiation for astronauts in space mission...SMJ Mortazavi
Exposure to high levels of space radiation and microgravity are two important concerns which need to be addressed before any long-term manned space mission. There are also reports showing that microgravity, through a synergistic effect, increases the radiation susceptibility of living organisms. Other researchers as well as our team have conducted some experiments on design and fabrication of appropriate radiation shields for spacecrafts. However, due to some cardinal barriers such as weight limitations and extreme inadequacy of current physical shields during extravehicular activity, we strongly believe that the physical shielding alone cannot solve the problem of potential exposure to high levels of radiation in a long-term space mission.
Therefore, over the past several years, we focused on two solutions; radioadaptive response and other biological-based radiation protection methods. Adaptive response, that is the increased radioresistance in cells or living organisms pre-exposed to a low adapting dose and then exposed to a high challenging dose, was firstly proposed by our team in 2003 as an effective method. This novel idea later formed the basis of many space radiation biology projects around the world.
Furthermore, conventional radioprotectors cannot efficiently be used in space due to limitations such as their considerable toxicity and the very narrow time window for their effective use (radioprotectors should be used before or at the time of exposure, while astronauts cannot estimate their doses before a solar particle event). Therefore, we focused on introducing natural radiation mitigators which could be efficiently used several hours after exposure (e.g. when a solar particle event subsides and astronauts are able to estimate their doses). In these experiments, radiation mitigators were introduced by our team which could be used even 24 hours after exposure to high levels of radiation caused by unpredictable sources such as SPEs.
Finally, some of our recent experiments were aimed at finding methods which could lead to boosting the immune system of astronauts during long-term missions. We investigated the effect of RF-EMFs-induced adaptive responses on immune system modulation in a mouse model of hindlimb unloading (HU). Hindlimb unloading rodent model is widely accepted by the scientific community as the model of choice for simulating spaceflight. In this study, serum levels of T helper cytokines were determined in HU mice, RF-EMF treated mice and HU mice pre-exposed to RF-EMF compared to those of untreated controls. The findings of this study will be published soon.
Assessment of Activity Concentration of The Naturally Occurring Radioactive M...IOSR Journals
The activity concentrations of potassium, Radium and thorium in soil samples from a mining site in yankandutse, Kaduna north western Nigeria were measured using gamma ray spectroscopy method. Activity concentration of potassium, Radium and thorium were determined. The activity concentrations of 40K, 226Ra and 232Th, respectively in Bq kg-1 in the soil samples ranged as follows: K-40 196.11±2.02 to 553.03±1.08 with average of 382.01, Ra-226 .1506±.03 to 5.67±.03 with average of 2.08 and Th-232 18.13±3.19 to 73.09±1.59 with average activity concentrations of 47.23 .The mean activity concentration of potassium and radium are below average but for thorium the activity concentration is above average.
- Comet C/2011 N3 (SOHO) was observed by the Solar Dynamics Observatory as it passed through the low solar corona in July 2011.
- The comet survived within the corona until it came within 0.146 solar radii (approximately 100,000 km) of the solar surface, at which point its extreme ultraviolet signal disappeared.
- Before being destroyed, material released from the comet was first seen in absorption against the solar corona, then formed an emission nebula as it interacted with the coronal plasma.
1) This document describes an ALMA survey of 126 submillimeter galaxies (SMGs) previously detected in the LABOCA ECDFS Submillimeter Survey (LESS).
2) The ALMA observations resolve the SMGs with an angular resolution of ∼1.6", doubling the number of interferometrically observed SMGs.
3) Preliminary results find that at least 35-50% of the LESS sources have been resolved into multiple SMGs, with the average number increasing with LESS flux density.
The document summarizes various methods for detecting water hazards outdoors, including:
- Color imagery, which identifies water by its reflections but struggles with still water.
- Short wave infrared imagery, which detects water's dark appearance in infrared. However, performance degrades where water reflects vegetation or clouds.
- Thermal infrared imagery, where water appears cooler than terrain by day and warmer at night, but only detects the top water layer.
- Laser range finders can detect water through specular reflection but are limited by range and angle of incidence.
- Multi-feature methods combine cues like brightness, texture and range but require significant computation.
- Polarization imaging exploits water's polarized light reflection
This document presents aluminum abundances for about 100 red giant stars in each of the Galactic globular clusters 47 Tuc and M 4. The abundances were derived from intermediate-resolution FLAMES/GIRAFFE spectra, focusing on the Al I doublet at 8772-8773 Å. Previous homogeneous abundances of O, Na, Mg, and Si were also analyzed to study multiple stellar populations in these clusters. The data confirm two stellar populations are visible in M 4, while 47 Tuc shows evidence of at least three distinct stellar groups based on the abundances of O, Na, Mg, Al, and N.
This document presents observations of ACT-CL J0102−4915, a massive galaxy cluster discovered by the Atacama Cosmology Telescope (ACT) via its strong Sunyaev-Zeldovich signal. Optical and X-ray observations reveal that it is undergoing a major merger between components with a mass ratio of 2:1 at a redshift of 0.87. Chandra X-ray data show significant temperature variations across the cluster from 6.6 keV to 22 keV, indicating a hot, luminous system undergoing a merger. The cluster appears to be an excellent example of a "bullet cluster" system at high redshift.
Improved two-photon imaging of living neurons in brain tissue through tempora...julian choy
This document describes a study that optimized two-photon imaging of living neurons in brain tissue by temporally gating the incident laser to reduce photon flux while maximizing fluorescence signal. The study found that gating the laser at the sampling frequency compromised cell viability despite high fluorescence. An optimum gating frequency range was identified that maintained cell viability while preserving fluorescence levels in two-photon images. Cell viability was monitored by measuring changes in membrane input resistance during whole-cell patch recording of neurons.
This document discusses a new design of plasmonic nanoantenna with a slant gap that can enhance optical chirality. The slant gap provides an enhanced electric field parallel to an external magnetic field with a phase delay of π/2, resulting in enhanced optical chirality in the near field. Numerical simulations show this nanoantenna design can generate a near field with enhanced optical chirality when excited by linearly polarized light. This enhanced optical chirality could allow for circular dichroism analysis using linearly polarized light and may find applications in analyzing the chirality of surface-bound matter.
How does biological protection help astronauts tolerate high levels of radiationSMJ Mortazavi
Abstract:
Exposure to high levels of space radiation and microgravity are two important concerns which need to be addressed before any long-term manned space mission. There are also reports showing that microgravity, through a synergistic effect, increases the radiation susceptibility of living organisms. Other researchers as well as our team have conducted some experiments on design and fabrication of appropriate radiation shields for spacecrafts. However, due to some cardinal barriers such as weight limitations and extreme inadequacy of current physical shields during extravehicular activity, we strongly believe that the physical shielding alone cannot solve the problem of potential exposure to high levels of radiation in a long-term space mission.
Therefore, over the past several years, we focused on two solutions; radioadaptive response and other biological-based radiation protection methods. Adaptive response, that is the increased radioresistance in cells or living organisms pre-exposed to a low adapting dose and then exposed to a high challenging dose, was firstly proposed by our team in 2003 as an effective method. This novel idea later formed the basis of many space radiation biology projects around the world.
Furthermore, conventional radioprotectors cannot efficiently be used in space due to limitations such as their considerable toxicity and the very narrow time window for their effective use (radioprotectors should be used before or at the time of exposure, while astronauts cannot estimate their doses before a solar particle event). Therefore, we focused on introducing natural radiation mitigators which could be efficiently used several hours after exposure (e.g. when a solar particle event subsides and astronauts are able to estimate their doses). In these experiments, radiation mitigators were introduced by our team which could be used even 24 hours after exposure to high levels of radiation caused by unpredictable sources such as SPEs.
Finally, some of our recent experiments were aimed at finding methods which could lead to boosting the immune system of astronauts during long-term missions. We investigated the effect of RF-EMFs-induced adaptive responses on immune system modulation in a mouse model of hindlimb unloading (HU). Hindlimb unloading rodent model is widely accepted by the scientific community as the model of choice for simulating spaceflight. In this study, serum levels of T helper cytokines were determined in HU mice, RF-EMF treated mice and HU mice pre-exposed to RF-EMF compared to those of untreated controls. The findings of this study will be published soon.
This document provides an overview of the basics of remote sensing. It defines remote sensing as acquiring information about an object without direct contact. It discusses key components of the remote sensing process including data acquisition, the electromagnetic spectrum, atmospheric interactions, spectral signatures, and satellite platforms and orbits. Remote sensing draws from many areas and plays an important role in monitoring the Earth through satellite imagery.
WE1.L10 - INTERANNUAL VARIABILITY IN CLIMATE PRODUCTS FROM THE ATMOSPHERIC IN...grssieee
The document summarizes the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite. AIRS measures atmospheric temperature and humidity profiles as well as greenhouse gases. It has provided over 8 years of global observations used to improve weather forecasts and validate climate models. AIRS data has also enabled over 350 research publications studying topics like tropical cyclones, the Madden-Julian oscillation, and trends in outgoing longwave radiation.
Wei Li has published extensively in international scientific journals and books as well as international conference proceedings. Some of his notable publications include papers on spectral characterization of monolithic mode-locked lasers, superluminescent diodes at 1.55 μm, characterization of 1550 nm Fabry-Perot laser structures, and invited chapters in books on dilute nitride semiconductors and GaInNAs quantum well lasers. He has also published work on extending the emission wavelength of GaInNAs/GaAs quantum well lasers beyond 1300 nm and high performance 1.32 μm GaInNAs/GaAs single-quantum-well lasers.
This document summarizes a study on errors in particle tracking microrheology. It separates errors into static errors from position measurements of immobilized particles due to limited spatial resolution, and dynamic errors from particle motion during the finite exposure time required for visualization. The authors develop models to calculate how these errors propagate to measurements of mean-squared displacement. They verify the models using simulations and experiments on viscous fluids, showing static errors can be corrected using static experiments at similar noise levels. This increases accuracy for microrheology studies.
Geoffroy Lerosey has published extensively in peer-reviewed journals, with over 35 publications. His work focuses on manipulating waves and controlling propagation at subwavelength scales using techniques like time reversal and metamaterials. Some of his publications have been highlighted in prominent journals and received significant attention.
This document summarizes Hubble Space Telescope ultraviolet spectroscopy of four white dwarfs known to accrete planetary debris. The spectra reveal absorption lines from a variety of metals including carbon, oxygen, aluminum, silicon, phosphorus, sulfur, chromium, iron, and nickel. Combined with optical data, between five and eleven different metals are detected in each white dwarf, indicating substantial chemical diversity in the accreted planetary debris. The abundances observed provide insights into the composition and origin of the debris, with some debris resembling bulk Earth composition and others showing evidence of melting and differentiation.
1) Observations of a Lyman-alpha nebula (LAB1) reveal that the Lyman-alpha emission is polarized, with a polarization fraction of around 20% at radii of 45 kpc from the center.
2) The detection of polarized radiation indicates that the Lyman-alpha photons were produced in the galaxies within the nebula and scattered by neutral hydrogen at large distances, rather than being produced in situ.
3) The polarization vectors are oriented tangentially to the overall geometry of the nebula, consistent with theoretical expectations for Lyman-alpha photons produced centrally and scattered at large radii.
1) The document presents new observations of shell structures in the halo of galaxy NGC 7600 and a movie from a cosmological simulation showing how shell galaxies can form in a cold dark matter universe.
2) The movie illustrates how the continuous accretion of dark matter and star clumps creates diffuse circumgalactic structures, and how the disruption of a massive clump on a near-radial orbit creates a complex system of concentric shells resembling those of NGC 7600.
3) With the aid of the simulation, the authors interpret NGC 7600 in the context of the cold dark matter model of galaxy formation through the accretion and disruption of smaller companion galaxies.
The document summarizes a study that uses strong and weak gravitational lensing to analyze the mass distribution of 28 galaxy clusters. Key findings include:
- The concentration parameter cvir is found to steeply decrease with increasing mass, approximately following cvir ∝ Mvir-0.59±0.12, consistent with theoretical predictions for high-mass clusters but observationally inferred concentrations are higher for lower-mass clusters possibly due to baryon cooling effects.
- Stacking weak lensing shear profiles also supports a steep mass-concentration relation.
- Stacking weak lensing shear maps with position angle information from strong lensing indicates significant ellipticity of the mean mass distribution, with a best-fit ellipticity
This document summarizes a study of lithium and sodium abundances in stars in the globular cluster M4. The authors obtained spectra for 91 main sequence and subgiant branch stars using the FLAMES spectrograph on the VLT. They detected a weak anti-correlation between lithium and sodium abundances among unevolved main sequence stars. Notably, one star, #37934, showed an unusually high lithium abundance, comparable to estimates of the primordial lithium abundance. This high lithium abundance, coupled with the star's sodium-rich nature, suggests the lithium may have come from pollution by a previous generation of stars, though preservation of the primordial abundance cannot be ruled out. The detection provides new evidence that globular clusters
Searching for signs_of_triggered_star_formation_toward_ic1848Sérgio Sacani
This document summarizes observations of three bright-rimmed clouds - SFO 11, SFO 11NE, and SFO 11E - associated with the HII region IC 1848, using submillimeter continuum data from SCUBA on the JCMT and molecular line data from CO isotopologues. The observations show evidence for protostellar cores within the clouds and recent or ongoing star formation. Based on the morphology and pressures inferred from the data, it is possible the UV illumination from the primary ionizing star HD17505 has triggered the collapse of dense molecular cores within SFO 11 and SFO 11E.
This study examines the clustering properties and redshift evolution of bias for 593 X-ray selected AGN from the XMM-Newton survey in the COSMOS field with spectroscopic redshifts below z=4. The authors find evidence that the bias factor increases with redshift for the total AGN population, from b=2.30 at z=0.92 to b=4.37 at z=1.94. Splitting the sample, they observe a similar increase in bias with redshift for broad-line and unobscured AGN, corresponding to a constant halo mass of logM~13.28 and logM~13, respectively. The observed bias factors cannot be reproduced by models assuming AGN are triggered
Modulations in the_radio_light_curve_of_the_typeiib_supernova_2001igSérgio Sacani
This document summarizes radio observations of the Type IIb supernova SN 2001ig made with the Australia Telescope Compact Array and Very Large Array over 700 days. The observations found periodic deviations from the standard model of radio light curves that are consistent with recurring density modulations in the circumstellar medium with a period of around 150 days. This provides evidence that the progenitor was a Wolf-Rayet star in a binary system with an eccentric 100 day orbit, causing regular build-up of circumstellar material. Such binary systems are thought to produce Type Ib/c supernovae through envelope stripping, linking these events to Type IIb supernovae.
This document is the lecture notes from an introductory astronomy course covering Chapter 15 on galaxies. It provides an overview of the course structure, learning objectives, quiz and exam schedule, and links to additional online resources and images of various galaxies presented in the Astronomy Picture of the Day.
The first hyper_luminous_infrared_galaxy_discovered_by_wiseSérgio Sacani
This document summarizes the discovery of WISE J181417.29+341224.9 (WISE 1814+3412), the first hyper-luminous infrared galaxy (LIR > 1013 L⊙) discovered by the Wide-field Infrared Survey Explorer (WISE). Follow-up images of WISE 1814+3412 revealed four nearby sources - a QSO, two Lyman Break Galaxies at z = 2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission and has a star formation rate of ~300M⊙ yr−1, accounting for <10% of the bolometric luminosity. An obscured AGN combined with starburst and
The first hyper_luminous_infrared_galaxy_discovered_by_wiseSérgio Sacani
This document summarizes the discovery of WISE J181417.29+341224.9 (WISE 1814+3412), the first hyper-luminous infrared galaxy (LIR > 1013 L⊙) discovered by the Wide-field Infrared Survey Explorer (WISE). Follow-up images of WISE 1814+3412 revealed four nearby sources - a QSO, two Lyman Break Galaxies at z=2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission of WISE 1814+3412 and has a star formation rate of ~300M⊙ yr−1, accounting for <10% of the total luminosity. An obscured
This document summarizes follow-up observations of galaxies selected from WISE as being hyperluminous. The authors observed 14 galaxies at 350-850 μm with SHARC-II and 18 galaxies at 1.1 mm with Bolocam, detecting 9 and 5 galaxies respectively. They also observed 25 targets at 3.6 and 4.5 μm with Spitzer and obtained optical spectra for 12 targets. By combining these data with WISE observations, they constructed mid-IR to millimeter spectral energy distributions that showed hotter dust temperatures than galaxy templates, estimated to be 60-120 K. These galaxies have infrared luminosities over 10^13 solar luminosities and represent an extreme population of luminous, hot dust-ob
Morphologies of mid-IR variability-selected AGN host galaxiesSérgio Sacani
This document summarizes a study that uses multi-epoch mid-infrared data from the Spitzer Extended Deep Survey to identify active galactic nuclei (AGN) through their variability over timescales of months to years. Around 1% of galaxies showed significant mid-IR variability, with 80% likely to be AGN. The morphologies of variable AGN host galaxies were compared to a control sample, finding that obscured AGN hosts show more weakly disturbed morphologies than strongly disturbed or normal galaxies. This suggests mid-IR variability selects obscured or "Compton-thick" AGN, revealing information about their host galaxy morphologies.
The discovery of_lensed_radio_and_x-ray_sources_behind_the_frontier_fields_cl...Sérgio Sacani
We report on high-resolution JVLA and Chandra observations of the Hubble Space Telescope (HST) Frontier Cluster
MACSJ0717.5+3745. MACSJ0717.5+3745 offers the largest contiguous magnified area of any known cluster,
making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0–6.5 GHz
JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the
HST imaging. Within this sample, we find sevenlensed sources with amplification factors larger than two. None of
these sources are identified as multiply lensed. Based on the radio luminosities, the majority of these sources are
likely star-forming galaxies with star-formation rates (SFRs) of 10–50 M: yr−1 located at 1 1 z 1 2. Two of the
lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely active galactic
nuclei, given their 2–10 keV X-ray luminosities of ∼1043–44 erg s−1. From the derived radio luminosity function, we
find evidence for an increase in the number density of radio sources at 0.6 z 2.0, compared to a z 0.3 sample.
Our observations indicate that deep radio imaging of lensing clusters can be used to study star-forming galaxies, with
SFRs as low as ∼10Me yr−1, at the peak of cosmic star formation history.
A Simultaneous dual-site technosignature search using international LOFAR sta...Sérgio Sacani
The Search for Extraterrestrial Intelligence (SETI) aims to find evidence of technosignatures, which
can point towards the possible existence of technologically advanced extraterrestrial life. Radio signals
similar to those engineered on Earth may be transmitted by other civilizations, motivating technosignature searches across the entire radio spectrum. In this endeavor, the low-frequency radio band
has remained largely unexplored; with prior radio searches primarily above 1 GHz. In this survey at
110 − 190 MHz, observations of 1,631,198 targets from TESS and Gaia are reported. Observations
took place simultaneously with two international stations (non-interferometric) of the Low Frequency
Array in Ireland and Sweden. We can reject the presence of any Doppler drifting narrow-band transmissions in the barycentric frame of reference, with equivalent isotropic radiated power of 1017 W, for
0.4 million (or 1.3 million) stellar systems at 110 (or 190) MHz. This work demonstrates the effectiveness of using multi-site simultaneous observations for rejecting anthropogenic signals in the search for
technosignatures.
This document summarizes the discovery and analysis of a Type Ia supernova (SN Ia) at a redshift of 1.71, the most distant spectroscopically confirmed SN Ia at the time. The Hubble Space Telescope was used to obtain spectroscopy and photometry of the supernova. Analysis of the spectroscopy confirms it as a SN Ia with 92% confidence. The photometry is used to determine the supernova's distance, which agrees with the predictions of the ΛCDM cosmological model. This distant supernova helps improve constraints on the nature and behavior of dark energy in the early universe.
A Search for Technosignatures Around 11,680 Stars with the Green Bank Telesco...Sérgio Sacani
We conducted a search for narrowband radio signals over four observing sessions in 2020–2023 with
the L-band receiver (1.15–1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the
telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of
∼11,860 stars and planetary systems in the ∼9 arcminute beam of the telescope. All detections were
either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. In
this work, we also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection
and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable
frequency range of the receiver and 98.7% of the injections when regions of dense RFI are excluded. In
another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ∼15 times
smaller at ∼6%. The pipeline efficiency affects SETI search volume calculations as well as calculations
of upper bounds on the number of transmitting civilizations. We developed an improved Drake Figure
of Merit for SETI search volume calculations that includes the pipeline efficiency and frequency drift
rate coverage. Based on our observations, we found that there is a high probability (94.0–98.7%) that
fewer than ∼0.014% of stars earlier than M8 within 100 pc host a transmitter that is detectable in
our search (EIRP > 1012 W). Finally, we showed that the UCLA SETI pipeline natively detects the
signals detected with AI techniques by Ma et al. (2023).
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
This document describes observations of the Seyfert 1 galaxy Mrk 509 using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST). The observations detected absorption features in the ultraviolet spectrum, which are attributed to outflowing gas from the active galactic nucleus as well as gas in the galaxy's interstellar medium and halo. The COS observations provide higher signal-to-noise and resolution than previous observations, detecting additional complexity in the absorption features. Variability in some features constrains the distances of absorbing gas components to be less than 250 pc and 1.5 kpc from the active nucleus. The absorption lines only partially cover the emission from the active nucleus, possibly due to
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
This paper presents a study of the extended X-ray emission in the Seyfert galaxy NGC 4151 using deep Chandra observations. Key findings include:
1) Emission line maps show strong OVII, OVIII, and NeIX line emission extending along the northeast-southwest direction, consistent with an ionization cone.
2) Spectral analysis finds the extended emission is well described by photoionized plasma models, supporting a dominant role for nuclear photoionization.
3) Faint extended emission is also seen perpendicular to the ionization cone, indicating some leakage of nuclear ionizing radiation through warm absorbers rather than being blocked by an obscuring torus.
GOALS-JWST: Unveiling Dusty Compact Sources in the Merging Galaxy IIZw096Sérgio Sacani
We have used the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) to obtain the first
spatially resolved, mid-infrared images of IIZw096, a merging luminous infrared galaxy (LIRG) at z = 0.036.
Previous observations with the Spitzer Space Telescope suggested that the vast majority of the total IR luminosity
(LIR) of the system originated from a small region outside of the two merging nuclei. New observations with
JWST/MIRI now allow an accurate measurement of the location and luminosity density of the source that is
responsible for the bulk of the IR emission. We estimate that 40%–70% of the IR bolometric luminosity, or
3–5 × 1011 Le, arises from a source no larger than 175 pc in radius, suggesting a luminosity density of at least
3–5 × 1012 Le kpc−2
. In addition, we detect 11 other star-forming sources, five of which were previously
unknown. The MIRI F1500W/F560W colors of most of these sources, including the source responsible for the
bulk of the far-IR emission, are much redder than the nuclei of local LIRGs. These observations reveal the power
of JWST to disentangle the complex regions at the hearts of merging, dusty galaxies.
This document presents the target selection process for the first year of the Breakthrough Listen search for intelligent life using the Green Bank Telescope, Parkes Telescope, and Automated Planet Finder. The targets include: 1) The 60 nearest stars within 5.1 parsecs to search for faint signals; 2) 1649 stars spanning stellar types from the Hipparcos catalog; 3) 123 nearby galaxies representing different morphological types to search billions of stars simultaneously; and 4) several classes of exotic objects like white dwarfs and neutron stars. The telescopes will observe 1,000,000 stars and galaxies at radio and optical wavelengths between 350 MHz to 100 GHz and 374-950nm, respectively, to search for technological signals.
A. Zakharov: Supermassive Black Hole at the Galactic CenterSEENET-MTP
The document summarizes research on the supermassive black hole at the center of the Milky Way galaxy. It discusses how Reinhard Genzel and Andrea Ghez received the 2012 Crafoord Prize in Astronomy for their observations of stars orbiting the galactic center, providing evidence of a supermassive black hole called Sagittarius A*. It also describes efforts to measure the shadow size of the black hole and constraints on its potential charge, finding that a significant negative charge is ruled out. Interferometric observations using radio telescopes aim to better understand properties of the black hole and test general relativity.
Measurements of a_massive_galaxy_clusterSérgio Sacani
This document reports on observations of IDCS J1426.5+3508, a galaxy cluster located at a redshift of 1.75. A Sunyaev-Zeldovich decrement was detected towards this cluster, indicating a total mass of 4.3×1014 solar masses. This makes it the most distant cluster detected via the Sunyaev-Zeldovich effect to date and the most massive cluster found at a redshift greater than 1.4. Despite its rarity, the cluster is not unexpected given cosmological models and the large area surveyed. However, it remains one of the rarest and most extreme clusters discovered and provides insight into the early formation of the most massive clusters.
The nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
The atacama cosmology_telescope_measuring_radio_galaxy_bias_through_cross_cor...Sérgio Sacani
A radiação cósmica de micro-ondas aponta para a matéria escura invisível, marcando o ponto onde jatos de material viajam a velocidades próximas da velocidade da luz, de acordo com uma equipe internacional de astrônomos. O principal autor do estudo, Rupert Allison da Universidade de Oxford apresentou os resultados no dia 6 de Julho de 2015 no National Astronomy Meeting em Venue Cymru, em Llandudno em Wales.
Atualmente, ninguém sabe ao certo do que a matéria escura é feita, mas ela é responsável por cerca de 26% do conteúdo de energia do universo, com galáxias massivas se formando em densas regiões de matéria escura. Embora invisível, a matéria escura se mostra através do efeito gravitacional – uma grande bolha de matéria escura puxa a matéria normal (como elétrons, prótons e nêutrons) através de sua própria gravidade, eventualmente se empacotando conjuntamente para criar as estrelas e galáxias inteiras.
Muitas das maiores dessas são galáxias ativas com buracos negros supermassivos em seus centros. Alguma parte do gás caindo diretamente na direção do buraco negro é ejetada como jatos de partículas e radiação. As observações feitas com rádio telescópios mostram que esses jatos as vezes se espalham por milhões de anos-luz desde a galáxia – mais distante até mesmo do que a extensão da própria galáxia.
Os cientistas esperam que os jatos possam viver em regiões onde existe um excesso de concentração da matéria escura, maior do que o da média. Mas como a matéria escura é invisível, testar essa ideia não é algo tão direto.
The most luminous_galaxies_discovered_by_wiseSérgio Sacani
This document presents a sample of 20 extremely luminous galaxies discovered by the Wide-field Infrared Survey Explorer (WISE). Five of these galaxies have infrared luminosities exceeding 1014 solar luminosities, the highest infrared luminosity threshold yet observed. They were selected using criteria requiring weak or no detection in the first two WISE bands but strong detections in the third and fourth bands. Spectral energy distribution modeling suggests their high luminosities are powered by obscured active galactic nuclei with hot dust temperatures around 450 Kelvin. The existence of such luminous galaxies at redshifts above 3 provides constraints on the early growth of supermassive black holes through rapid accretion.
Obscuration beyond the nucleus: infrared quasars can be buried in extreme com...Sérgio Sacani
This document discusses how infrared quasars can be obscured by compact starbursts in their host galaxies in addition to the canonical dusty torus. The key points are:
1) Infrared quasars in starburst galaxies with star formation rates above 300 solar masses per year have a higher obscured fraction than at lower star formation rates, suggesting the host galaxy interstellar medium can significantly contribute to obscuring the quasar.
2) At star formation rates above 300 solar masses per year, submillimeter galaxies and infrared quasars have similarly compact submillimeter sizes of 0.5-3 kiloparsecs, indicating the dense interstellar medium in these compact starbursts can heavily obscure the quasar, even reaching
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
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)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
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Ca-rich population. Although such an object is too red for any low-
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cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
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) with
Λ
CDM. Therefore unlike low-
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Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
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truly diverge from their low-
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counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Driving Business Innovation: Latest Generative AI Advancements & Success StorySafe Software
Are you ready to revolutionize how you handle data? Join us for a webinar where we’ll bring you up to speed with the latest advancements in Generative AI technology and discover how leveraging FME with tools from giants like Google Gemini, Amazon, and Microsoft OpenAI can supercharge your workflow efficiency.
During the hour, we’ll take you through:
Guest Speaker Segment with Hannah Barrington: Dive into the world of dynamic real estate marketing with Hannah, the Marketing Manager at Workspace Group. Hear firsthand how their team generates engaging descriptions for thousands of office units by integrating diverse data sources—from PDF floorplans to web pages—using FME transformers, like OpenAIVisionConnector and AnthropicVisionConnector. This use case will show you how GenAI can streamline content creation for marketing across the board.
Ollama Use Case: Learn how Scenario Specialist Dmitri Bagh has utilized Ollama within FME to input data, create custom models, and enhance security protocols. This segment will include demos to illustrate the full capabilities of FME in AI-driven processes.
Custom AI Models: Discover how to leverage FME to build personalized AI models using your data. Whether it’s populating a model with local data for added security or integrating public AI tools, find out how FME facilitates a versatile and secure approach to AI.
We’ll wrap up with a live Q&A session where you can engage with our experts on your specific use cases, and learn more about optimizing your data workflows with AI.
This webinar is ideal for professionals seeking to harness the power of AI within their data management systems while ensuring high levels of customization and security. Whether you're a novice or an expert, gain actionable insights and strategies to elevate your data processes. Join us to see how FME and AI can revolutionize how you work with data!
Have you ever been confused by the myriad of choices offered by AWS for hosting a website or an API?
Lambda, Elastic Beanstalk, Lightsail, Amplify, S3 (and more!) can each host websites + APIs. But which one should we choose?
Which one is cheapest? Which one is fastest? Which one will scale to meet our needs?
Join me in this session as we dive into each AWS hosting service to determine which one is best for your scenario and explain why!
Generating privacy-protected synthetic data using Secludy and MilvusZilliz
During this demo, the founders of Secludy will demonstrate how their system utilizes Milvus to store and manipulate embeddings for generating privacy-protected synthetic data. Their approach not only maintains the confidentiality of the original data but also enhances the utility and scalability of LLMs under privacy constraints. Attendees, including machine learning engineers, data scientists, and data managers, will witness first-hand how Secludy's integration with Milvus empowers organizations to harness the power of LLMs securely and efficiently.
The Microsoft 365 Migration Tutorial For Beginner.pptxoperationspcvita
This presentation will help you understand the power of Microsoft 365. However, we have mentioned every productivity app included in Office 365. Additionally, we have suggested the migration situation related to Office 365 and how we can help you.
You can also read: https://www.systoolsgroup.com/updates/office-365-tenant-to-tenant-migration-step-by-step-complete-guide/
HCL Notes and Domino License Cost Reduction in the World of DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-and-domino-license-cost-reduction-in-the-world-of-dlau/
The introduction of DLAU and the CCB & CCX licensing model caused quite a stir in the HCL community. As a Notes and Domino customer, you may have faced challenges with unexpected user counts and license costs. You probably have questions on how this new licensing approach works and how to benefit from it. Most importantly, you likely have budget constraints and want to save money where possible. Don’t worry, we can help with all of this!
We’ll show you how to fix common misconfigurations that cause higher-than-expected user counts, and how to identify accounts which you can deactivate to save money. There are also frequent patterns that can cause unnecessary cost, like using a person document instead of a mail-in for shared mailboxes. We’ll provide examples and solutions for those as well. And naturally we’ll explain the new licensing model.
Join HCL Ambassador Marc Thomas in this webinar with a special guest appearance from Franz Walder. It will give you the tools and know-how to stay on top of what is going on with Domino licensing. You will be able lower your cost through an optimized configuration and keep it low going forward.
These topics will be covered
- Reducing license cost by finding and fixing misconfigurations and superfluous accounts
- How do CCB and CCX licenses really work?
- Understanding the DLAU tool and how to best utilize it
- Tips for common problem areas, like team mailboxes, functional/test users, etc
- Practical examples and best practices to implement right away
What is an RPA CoE? Session 1 – CoE VisionDianaGray10
In the first session, we will review the organization's vision and how this has an impact on the COE Structure.
Topics covered:
• The role of a steering committee
• How do the organization’s priorities determine CoE Structure?
Speaker:
Chris Bolin, Senior Intelligent Automation Architect Anika Systems
Skybuffer SAM4U tool for SAP license adoptionTatiana Kojar
Manage and optimize your license adoption and consumption with SAM4U, an SAP free customer software asset management tool.
SAM4U, an SAP complimentary software asset management tool for customers, delivers a detailed and well-structured overview of license inventory and usage with a user-friendly interface. We offer a hosted, cost-effective, and performance-optimized SAM4U setup in the Skybuffer Cloud environment. You retain ownership of the system and data, while we manage the ABAP 7.58 infrastructure, ensuring fixed Total Cost of Ownership (TCO) and exceptional services through the SAP Fiori interface.
Connector Corner: Seamlessly power UiPath Apps, GenAI with prebuilt connectorsDianaGray10
Join us to learn how UiPath Apps can directly and easily interact with prebuilt connectors via Integration Service--including Salesforce, ServiceNow, Open GenAI, and more.
The best part is you can achieve this without building a custom workflow! Say goodbye to the hassle of using separate automations to call APIs. By seamlessly integrating within App Studio, you can now easily streamline your workflow, while gaining direct access to our Connector Catalog of popular applications.
We’ll discuss and demo the benefits of UiPath Apps and connectors including:
Creating a compelling user experience for any software, without the limitations of APIs.
Accelerating the app creation process, saving time and effort
Enjoying high-performance CRUD (create, read, update, delete) operations, for
seamless data management.
Speakers:
Russell Alfeche, Technology Leader, RPA at qBotic and UiPath MVP
Charlie Greenberg, host
For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2024/06/how-axelera-ai-uses-digital-compute-in-memory-to-deliver-fast-and-energy-efficient-computer-vision-a-presentation-from-axelera-ai/
Bram Verhoef, Head of Machine Learning at Axelera AI, presents the “How Axelera AI Uses Digital Compute-in-memory to Deliver Fast and Energy-efficient Computer Vision” tutorial at the May 2024 Embedded Vision Summit.
As artificial intelligence inference transitions from cloud environments to edge locations, computer vision applications achieve heightened responsiveness, reliability and privacy. This migration, however, introduces the challenge of operating within the stringent confines of resource constraints typical at the edge, including small form factors, low energy budgets and diminished memory and computational capacities. Axelera AI addresses these challenges through an innovative approach of performing digital computations within memory itself. This technique facilitates the realization of high-performance, energy-efficient and cost-effective computer vision capabilities at the thin and thick edge, extending the frontier of what is achievable with current technologies.
In this presentation, Verhoef unveils his company’s pioneering chip technology and demonstrates its capacity to deliver exceptional frames-per-second performance across a range of standard computer vision networks typical of applications in security, surveillance and the industrial sector. This shows that advanced computer vision can be accessible and efficient, even at the very edge of our technological ecosystem.
For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2024/06/temporal-event-neural-networks-a-more-efficient-alternative-to-the-transformer-a-presentation-from-brainchip/
Chris Jones, Director of Product Management at BrainChip , presents the “Temporal Event Neural Networks: A More Efficient Alternative to the Transformer” tutorial at the May 2024 Embedded Vision Summit.
The expansion of AI services necessitates enhanced computational capabilities on edge devices. Temporal Event Neural Networks (TENNs), developed by BrainChip, represent a novel and highly efficient state-space network. TENNs demonstrate exceptional proficiency in handling multi-dimensional streaming data, facilitating advancements in object detection, action recognition, speech enhancement and language model/sequence generation. Through the utilization of polynomial-based continuous convolutions, TENNs streamline models, expedite training processes and significantly diminish memory requirements, achieving notable reductions of up to 50x in parameters and 5,000x in energy consumption compared to prevailing methodologies like transformers.
Integration with BrainChip’s Akida neuromorphic hardware IP further enhances TENNs’ capabilities, enabling the realization of highly capable, portable and passively cooled edge devices. This presentation delves into the technical innovations underlying TENNs, presents real-world benchmarks, and elucidates how this cutting-edge approach is positioned to revolutionize edge AI across diverse applications.
"Frontline Battles with DDoS: Best practices and Lessons Learned", Igor IvaniukFwdays
At this talk we will discuss DDoS protection tools and best practices, discuss network architectures and what AWS has to offer. Also, we will look into one of the largest DDoS attacks on Ukrainian infrastructure that happened in February 2022. We'll see, what techniques helped to keep the web resources available for Ukrainians and how AWS improved DDoS protection for all customers based on Ukraine experience
Northern Engraving | Nameplate Manufacturing Process - 2024Northern Engraving
Manufacturing custom quality metal nameplates and badges involves several standard operations. Processes include sheet prep, lithography, screening, coating, punch press and inspection. All decoration is completed in the flat sheet with adhesive and tooling operations following. The possibilities for creating unique durable nameplates are endless. How will you create your brand identity? We can help!
AppSec PNW: Android and iOS Application Security with MobSFAjin Abraham
Mobile Security Framework - MobSF is a free and open source automated mobile application security testing environment designed to help security engineers, researchers, developers, and penetration testers to identify security vulnerabilities, malicious behaviours and privacy concerns in mobile applications using static and dynamic analysis. It supports all the popular mobile application binaries and source code formats built for Android and iOS devices. In addition to automated security assessment, it also offers an interactive testing environment to build and execute scenario based test/fuzz cases against the application.
This talk covers:
Using MobSF for static analysis of mobile applications.
Interactive dynamic security assessment of Android and iOS applications.
Solving Mobile app CTF challenges.
Reverse engineering and runtime analysis of Mobile malware.
How to shift left and integrate MobSF/mobsfscan SAST and DAST in your build pipeline.
Discover top-tier mobile app development services, offering innovative solutions for iOS and Android. Enhance your business with custom, user-friendly mobile applications.
5th LF Energy Power Grid Model Meet-up SlidesDanBrown980551
5th Power Grid Model Meet-up
It is with great pleasure that we extend to you an invitation to the 5th Power Grid Model Meet-up, scheduled for 6th June 2024. This event will adopt a hybrid format, allowing participants to join us either through an online Mircosoft Teams session or in person at TU/e located at Den Dolech 2, Eindhoven, Netherlands. The meet-up will be hosted by Eindhoven University of Technology (TU/e), a research university specializing in engineering science & technology.
Power Grid Model
The global energy transition is placing new and unprecedented demands on Distribution System Operators (DSOs). Alongside upgrades to grid capacity, processes such as digitization, capacity optimization, and congestion management are becoming vital for delivering reliable services.
Power Grid Model is an open source project from Linux Foundation Energy and provides a calculation engine that is increasingly essential for DSOs. It offers a standards-based foundation enabling real-time power systems analysis, simulations of electrical power grids, and sophisticated what-if analysis. In addition, it enables in-depth studies and analysis of the electrical power grid’s behavior and performance. This comprehensive model incorporates essential factors such as power generation capacity, electrical losses, voltage levels, power flows, and system stability.
Power Grid Model is currently being applied in a wide variety of use cases, including grid planning, expansion, reliability, and congestion studies. It can also help in analyzing the impact of renewable energy integration, assessing the effects of disturbances or faults, and developing strategies for grid control and optimization.
What to expect
For the upcoming meetup we are organizing, we have an exciting lineup of activities planned:
-Insightful presentations covering two practical applications of the Power Grid Model.
-An update on the latest advancements in Power Grid -Model technology during the first and second quarters of 2024.
-An interactive brainstorming session to discuss and propose new feature requests.
-An opportunity to connect with fellow Power Grid Model enthusiasts and users.
Energy Efficient Video Encoding for Cloud and Edge Computing Instances
Wise agn black_hole_01
1. Accepted to the Astrophysical Journal (April 24, 2012)
Mid-Infrared Selection of AGN with the Wide-Field Infrared Survey Explorer.
I. Characterizing WISE-Selected AGN in COSMOS
arXiv:1205.0811v1 [astro-ph.CO] 3 May 2012
Daniel Stern1 , Roberto J. Assef1,2 , Dominic J. Benford3 , Andrew Blain4 , Roc Cutri5 , Arjun Dey6 ,
Peter Eisenhardt1 , Roger L. Griffith5 , T.H. Jarrett5 , Sean Lake7 , Frank Masci5 , Sara Petty7 , S.A.
Stanford8,9 , Chao-Wei Tsai5 , E.L. Wright7 , Lin Yan5 , Fiona Harrison10 & Kristin Madsen10
ABSTRACT
The Wide-field Infrared Survey Explorer (WISE) is an extremely capable and effi-
cient black hole finder. We present a simple mid-infrared color criterion, W 1−W 2 ≥ 0.8
(i.e., [3.4]−[4.6] ≥ 0.8, Vega), which identifies 61.9 ± 5.4 AGN candidates per deg2 to a
depth of W 2 ∼ 15.0. This implies a much larger census of luminous AGN than found by
typical wide-area surveys, attributable to the fact that mid-infrared selection identifies
both unobscured (type 1) and obscured (type 2) AGN. Optical and soft X-ray surveys
alone are highly biased towards only unobscured AGN, while this simple WISE selection
likely identifies even heavily obscured, Compton-thick AGN. Using deep, public data in
the COSMOS field, we explore the properties of WISE-selected AGN candidates. At the
mid-infrared depth considered, 160 µJy at 4.6 µm, this simple criterion identifies 78%
of Spitzer mid-infrared AGN candidates according to the criteria of Stern et al. (2005)
and the reliability is 95%. We explore the demographics, multiwavelength properties
and redshift distribution of WISE-selected AGN candidates in the COSMOS field.
Subject headings: surveys: infrared — AGN
1
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221,
Pasadena, CA 91109 [e-mail: daniel.k.stern@jpl.nasa.gov]
2
NASA Postdoctoral Program Fellow
3
NASA Goddard Space Flight Center, Code 665, Greenbelt, MD 20771
4
Department of Physics and Astronomy, University of Leicester, LE1 7RH Leicester, UK
5
Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125
6
National Optical Astronomical Observatory, 950 N. Cherry Ave., Tucson, AZ 85719
7
Physics and Astronomy Department, University of California, Los Angeles, CA 90095
8
Department of Physics, University of California, One Shields Avenue, Davis, CA 95616
9
Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550
10
Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125
2. –2–
1. Introduction
Most surveys for AGN are severely biased towards unobscured (type 1) AGN. Nuclear emission
in such sources dominates over host galaxy light at most wavelengths, making type 1 AGN both
more readily identifiable and easier to follow-up spectroscopically. However, models predict a large
population of obscured (type 2) AGN, outnumbering type 1 AGN by a factor of ∼ 3 (e.g., Comastri
et al. 1995; Treister et al. 2004; Ballantyne et al. 2011). Determining the ratio of unobscured
to obscured AGN as a function of luminosity and redshift has direct implications for the growth
history of supermassive black holes in galactic centers, as well as for the origin of the cosmic X-
ray background (and, at a ∼ 10% level, optical and infrared backgrounds). Furthermore, recent
theoretical work suggests that AGN feedback plays a dominant role in establishing the present-day
appearances of galaxies (e.g., Silk & Rees 1998; Hopkins et al. 2008). With the dominant population
of obscured AGN severely underrepresented by current studies, however, a full understanding of
the interplay between AGN feedback and galaxy formation is hampered.
The most promising photometric techniques for identifying luminous type 2 AGN are radio
selection, hard X-ray selection and mid-infrared selection. However, only ∼ 10% of AGN are radio-
loud (e.g., Stern et al. 2000b) and the current generation of hard X-ray satellites have limited
sensitivity. Specifically, recent surveys with Swift and INTEGRAL have only identified a few dozen
heavily obscured (e.g., Compton-thick) AGN, all at very low redshift, z ≈ 0 (e.g., Bassani et al.
1999; Vignali & Comastri 2002; Ajello et al. 2008; Tueller et al. 2008; Burningham et al. 2011).
The Nuclear Spectroscopic Telescope Array (NuSTAR) (Harrison et al. 2010), scheduled for launch
in early 2012, will improve that hard X-ray (∼ 30 keV) sensitivity by a factor of ∼ 200, but with
a field of view comparable to Chandra/ACIS, NuSTAR will only undertake a limited number of
extragalactic surveys, unlikely to cover more than a few square degrees of sky. With mid-infrared
sensitivities several orders of magnitude greater than the Infrared Astronomical Satellite (IRAS),
the Wide-field Infrared Survey Explorer (WISE) (Wright et al. 2010) promises the first sensitive
full-sky survey for both type 1 and type 2 luminous AGN.
WISE launched on UT 2009 December 14 and completed its first survey of the entire sky on UT
2010 July 17, obtaining a minimum coverage of five exposures per sky position over 95% of the sky
in four passbands, 3.4, 4.6, 12 and 22 µm (W 1, W 2, W 3 and W 4). The all-sky data release occurred
on 2012 March 14, releasing all data taken during the WISE full cryogenic mission phase11 . The
median depth-of-coverage is 15.6 exposures per sky position for W 1 and W 2, and 14.8 exposures
per sky position for W 3 and W 4. Accounting for source confusion, the estimated sensitivities are
0.068, 0.098, 0.86 and 5.4 mJy (5σ), respectively (Wright et al. 2010). The corresponding Vega
magnitude limits are 16.83, 15.60, 11.32, and 8.0, respectively. The depth increases with ecliptic
latitude, reaching more than five times greater sensitivity near the ecliptic poles (Jarrett et al.
′′ ′′ ′′ ′′
2011). In order of increasing wavelength, the imaging resolution (FWHM) is 6. 1, 6. 4, 6. 5 and 12. 0
11
See http://wise2.ipac.caltech.edu/docs/release/allsky/.
3. –3–
for the four bands.
Similar to the UV-excess method of identifying quasars (e.g., Schmidt & Green 1983), mid-
infrared selection of AGN relies on distinguishing the approximately power-law AGN spectrum from
the black body stellar spectrum of galaxies which peaks at rest-frame 1.6µm. Mid-infrared data
easily separate AGN from stars and galaxies, with the added benefit that mid-infrared selection
is less susceptible to dust extinction and is sensitive to the highest redshift sources. Courtesy the
unprecedented sensitivity and mapping efficiency of the Infrared Array Camera (IRAC; Fazio et al.
2004) onboard the Spitzer Space Telescope, the past few years have seen an explosion of research
using mid-infrared observations to find and study (obscured) AGN at high redshift (e.g., Lacy et al.
2004, 2007; Stern et al. 2005; Alonso-Herrero et al. 2006; Barmby et al. 2006; Mart´
ınez-Sansigre et al.
2006, 2007; Donley et al. 2007, 2008, 2012; Dey et al. 2008; Fiore et al. 2008, 2009; Hatziminaoglou
et al. 2008; Rigopoulou et al. 2009; Seymour et al. 2007; De Breuck et al. 2010; Eckart et al.
2010; Park et al. 2010). IRAC identification of AGN typically required all four passbands of that
instrument, with data out to 8µm, to differentiate AGN from high-redshift (z > 1.3) massive
∼
galaxies. This is because distant, massive galaxies have red observed colors from 3 to 5 µm (e.g.,
Lacy et al. 2004; Stern et al. 2005; Donley et al. 2007, 2012; Hickox et al. 2009; Galametz et al.
2012) and even very shallow (< 90 sec) IRAC pointings easily reach well below the characteristic
brightness of early-type galaxies out to z ∼ 2, m∗ ≈ 16.7 (e.g., Mancone et al. 2010). Courtesy of
4.5
its shallow observations, WISE suffers less pronouncedly from such contamination and therefore is
able to robustly identify AGN with just the two bluest, most sensitive channels.
Fig. 1 illustrates WISE selection of AGN. As anticipated prior to the launch of WISE in Ashby
et al. (2009), Assef et al. (2010) and Eckart et al. (2010), a simple W 1 − W 2 color cut robustly
differentiates AGN from stars and galaxies. Since the public release of WISE data, several teams
have also noted the efficiency with which WISE identifies AGN (e.g., D’Abrusco et al. 2012; Edelson
& Malkan 2012; Massaro et al. 2012), though these analyses have used the full four-band WISE
photometry. Using the empirical AGN and galaxy spectral templates of Assef et al. (2010), Fig. 1
shows how W 1 − W 2 color evolves with redshift. The left panel considers a pure AGN template
with increasing amounts of dust extinction while the right panel considers an unobscured AGN
increasingly diluted by stellar emission (modeled with the elliptical galaxy, or E, template). AGN
fraction refers to the fraction of the integrated emission in the rest-frame 0.1 − 30 µm range of the
unextincted templates which comes from the AGN.
Out to z ∼ 3.5, pure AGN have red W 1 − W 2 mid-infrared colors. Beyond this redshift, the
templates become blue as the ∼ 1µm minimum in the AGN template shifts into the W 2 band (see
also Richards et al. 2006a). Hα emission shifting into the W 1 band plays an additional role in
causing blue W 1 − W 2 colors for AGN at z > 3.4 (Assef et al. 2010). Even modest amounts of dust
∼
extinction redden the observed W 1−W 2 colors for high-redshift AGN. Heavily extincted pure AGN
are extremely red; for example, a pure AGN reddened by E(B − V ) = 15 has W 1 − W 2 > 2 at all
redshifts. Mid-infrared selection of AGN is remarkably robust at identifying pure AGN regardless of
redshift. Indeed, Blain et al. (2012) report on the WISE detection of many of the highest redshift,
4. –4–
Fig. 1.— Model colors of AGN as a function of redshift using the templates of Assef et al. (2010;
Vega magnitudes). The left panel shows a pure AGN template with increasing amounts of dust
extinction. The right panel shows an unextincted AGN diluted by increasing amounts of host
galaxy light, where the host is the early-type (E) template from Assef et al. (2010); changing
galaxy template has minimal effect. A simple color criterion of W 1 − W 2 ≥ 0.8 identifies pure
AGN out to z ∼ 3 and extincted pure AGN out to higher redshifts. For unextincted AGN, sources
are no longer selected as the host galaxy becomes an increasing fraction of the bolometric luminosity.
z > 6 quasars known, including the recently discovered z = 7.085 quasar from the United Kingdom
Infrared Deep Sky Survey (UKIDSS; Mortlock et al. 2011). That quasar, the most distant currently
known, has W 1 − W 2 ∼ 1.2.
In contrast, normal galaxies and Galactic sources are unlikely to present such red W 1 − W 2
colors. The galaxy templates of Assef et al. (2010) are blue in this WISE color combination,
with W 1 − W 2 ≤ 0.8 out to z ∼ 1.2. Given the shallow sensitivity of WISE, only the tip of the
galaxy luminosity function will be well-detected by WISE at higher redshifts, particularly when
5. –5–
Fig. 2.— Model colors of an extincted AGN as a function of redshift for increasing contributions
of host galaxy light. As per Fig. 1, models use the AGN and early-type (E) galaxy templates of
Assef et al. (2010; Vega magnitudes); changing the galaxy template has minimal effect. The left
panel shows a modestly extincted AGN with E(B − V ) = 1, corresponding to NH ∼ 6 × 1022 cm−2 ,
while the right panels shows a heavily extincted AGN with E(B − V ) = 10, corresponding to
NH ∼ 6 × 1023 cm−2 . For modest levels of extinction, the results are essentially unchanged from
the right panel of Fig. 1: a simple color criterion of W 1 − W 2 ≥ 0.8 identifies AGN-dominated
galaxies so long as the AGN fraction is > 80%. For heavily extincted AGN, including Compton-thick
∼
AGN (NH > 1024 cm−2 ), the mid-infrared emission becomes dominated by the host galaxy above
∼
redshifts of a few tenths, essentially regardless of AGN fraction, making it difficult to distinguish
such systems from normal galaxies.
the analysis is restricted to the very conservative, 10σ flux limit (W 2 ∼ 15.0) we apply in this
paper. In terms of Galactic contamination, only the coolest brown dwarfs and the most heavily
dust-reddened stars will exhibit such red WISE colors. Kirkpatrick et al. (2011) show that stars
of spectral class later (e.g., cooler) than ∼ T1 have W 1 − W 2 ≥ 0.8; these red colors are caused
6. –6–
by methane absorption in the W 1 band (see also Cushing et al. 2011). In a high Galactic latitude
survey, neither cool brown dwarfs nor dust-reddened stars will be significant contaminants at the
flux limit of WISE.
As seen in the right panel of Fig. 1, dilution by the host galaxy will cause blue W 1 − W 2
colors, making less powerful AGN no longer identifiable using this simple WISE color criterion.
This illustrates a powerful synergy between X-ray and mid-infrared surveys. While sensitive soft
X-ray (≤ 10 keV) surveys are quite powerful at identifying even low-luminosity AGN since stellar
processes are unlikely to power X-ray emission at luminosities greater than ∼ 1042 erg s−1 (e.g.,
Stern et al. 2002a; Brandt & Hasinger 2005), such surveys are not sensitive to heavily obscured
AGN since the low energy X-rays are readily absorbed and scattered. This is particularly true for
heavily obscured low-redshift sources; higher redshift obscured AGN are helped by advantageous
k-corrections (e.g., Stern et al. 2002b). Mid-infrared surveys, in contrast, readily identify the most
heavily obscured, luminous AGN since the obscuring material is thermally heated by the AGN and
emits relatively unimpeded by dust extinction. However, dilution by the host galaxy limits mid-
infrared surveys from identifying low luminosity AGN. Optical photometric surveys are the most
heavily biased, with a sensitivity largely restricted to the least obscured, most luminous AGN.
Using data from deep Chandra and Spitzer imaging of targeted surveys, significant advances have
come in recent years at understanding the full census of AGN (e.g., Polletta et al. 2006; Hickox et al.
2007; Fiore et al. 2008; Gorjian et al. 2008; Comastri et al. 2011; Hickox et al. 2011; Mullaney et al.
2011). Combining WISE with soft X-ray data from the all-sky eROSITA telescope on Spectrum
R¨ntgen Gamma (SRG) (Predehl et al. 2010), expected to launch in late 2013, will extend the
o
results of these targeted surveys across the full sky.
How will WISE perform at identifying the most heavily obscured, Compton-thick AGN?
Assuming an SMC-like gas-to-dust ratio (NH ∼ 2 × 1022 cm−2 mag−1 ; Maiolino et al. 2001),
NH ∼ 1024 cm−2 corresponds to AV ∼ 50, or E(B − V ) ∼ 15 for RV ∼ 3.1 (e.g., Cardelli et al. 1989;
Gordon & Clayton 1998; York et al. 2006). As can be inferred from the left panel of Fig. 1, such
heavily obscured AGN will have very red W 1 − W 2 colors at any redshift. However, host galaxy
dilution in these bands will become significant as extreme obscuration hides the AGN. As shown in
Fig. 2, the effect is subtle for modestly extincted sources with NH < 6 × 1022 cm−2 , corresponding
∼
to E(B − V ) < 1. Such AGN should be readily identifiable from their W 1 − W 2 colors so long
∼
as the AGN is bolometrically dominant. However, the blue mid-infrared colors of the host stellar
populations across these WISE bands will make low-redshift, heavily obscured AGN difficult to
identify at mid-infrared wavelengths. At higher redshifts, z > 1.5, the host galaxy becomes red
∼
across these bands, but also fades below the detection limit of WISE. The most heavily-obscured
AGN are most likely best identified using the longer wavelength WISE passbands. However, the
cost is that the diminished sensitivity of those bands limits searches to the most luminous sources.
Indeed, Eisenhardt et al. (2012) report on a WISE-selected source which is undetected in W 1 and
W 2, but has very red W 2 − W 3 colors. Similarly selected sources are further discussed in Bridge
et al. (2012) and Wu et al. (2012); we find only ∼ 1000 such extreme sources across the full sky.
7. –7–
This paper reports on WISE-selected AGN in the Cosmic Evolution Survey (COSMOS; Scoville
et al. 2007). We use this well studied field, which includes deep, public, panchromatic imaging from
the radio to the X-ray in order to both establish WISE AGN selection criteria and to understand
the multi-wavelength properties of WISE-selected AGN. Our selection criterion identifies 130 AGN
candidates in COSMOS, which is sufficient for some investigations but is too small for evolutionary
studies. A companion paper, Assef et al. (2012), uses the wider area Bo¨tes field in order to
o
investigate the luminosity distribution and evolution of WISE-selected AGN.
This paper is organized as follows. Section 2 discusses how the WISE and COSMOS data were
matched, and motivates the simple W 1 − W 2 ≥ 0.8 criterion we use to identify AGN candidates.
Section 3 describes the multiwavelength properties of WISE-selected AGN, ranging from their
demographics to their Hubble Space Telescope morphologies to their redshift distribution. As part
of this investigation, we obtained Keck spectroscopy of mid-infrared selected AGN candidates in
the COSMOS field, described in § 3.7. Section 4 summarizes our results. Since COSMOS is a
well-studied field, of interest to a broad segment of the astrophysical community, we include an
Appendix tabulating 26 additional COSMOS sources for which we obtained spectroscopic redshifts.
Unless otherwise specified, we use Vega magnitudes throughout and adopt the concordance
cosmology, ΩM = 0.3, ΩΛ = 0.7 and H0 = 70 km s−1 Mpc−1 .
2. WISE Selection of AGN in the COSMOS Field
2.1. Matching WISE with S-COSMOS
The Spitzer-COSMOS survey (S-COSMOS; Sanders et al. 2007) carried out a deep (620 hr),
uniform survey of the full 2 deg2 COSMOS field in all seven Spitzer bands (3.6, 4.5, 5.8, 8.0, 24, 70
and 160 µm). The IRAC portion of the survey covered the field to a depth of 1200 s in the four
bluest bands of Spitzer, with 5σ measured sensitivities ranging from 0.9µJy at 3.6µm to 14.6µJy at
8.0µm. The longer wavelength observations, obtained with the Multiband Imaging Photometer for
Spitzer (MIPS; Rieke et al. 2004), reach 5σ sensitivities of approximately 0.07, 8.5 and 65 mJy for
the 24, 70, and 160 µm arrays, respectively (Frayer et al. 2009). These depths are all considerably
deeper than WISE.
We identified 6261 unique WISE sources with signal-to-noise ratio SN R ≥ 10 in WISE band
W 2 in a region that extends slightly beyond the field of view (FoV) of the S-COSMOS survey.
We used a preliminary version of the second pass data, which co-adds all observations from the
WISE mission. In order to avoid spurious and poorly photometered sources, we limited the sample
to relatively isolated sources by requiring blend flag N B ≤ 2. We also avoided contaminated or
confused sources by eliminating sources whose W 1 or W 2 photometry was affected by diffraction
spikes (ccf lag = D), persistence (ccf lag = P ), scattered light haloes from nearby bright sources
(ccf lag = H), or optical ghosts (ccf lag = O) (for a detailed description of WISE catalog variables,
8. –8–
Fig. 3.— Distribution of offsets between WISE and S-COSMOS photometry for the two bluest
WISE passbands: W 1 − [3.6] is plotted as a solid line, W 2 − [4.5] is plotted as a dotted line.
see Wright et al. 2010). The preliminary version of the second pass data we used double counts
′′
sources in the overlap regions between processing stripes. Using a 0. 5 match radius, we identified
duplicated sources in this preliminary catalog and only retained the source with higher signal-to-
noise ratio in W 1. The conservative (10σ) W 2 depth we apply corresponds to an approximate flux
density limit of 15.05 mag (∼ 160 µJy) at 4.6 µm. Most sources are also detected at ≥ 10σ at 3.4
µm, corresponding to 16.45 mag (∼ 70 µJy).
We then identified the nearest S-COSMOS source to each WISE source. We required detections
in both IRAC channel 1 (3.6 µm) and channel 2 (4.5 µm) in order to avoid the edges of S-COSMOS
which did not receive full four-band IRAC coverage. We also eliminated saturated stars with the
requirement [3.6] ≥ 11. Correcting for the small mean astrometric offset between WISE and
′′ ′′ ′′
S-COSMOS, ∆R.A. = 0. 108 and ∆Dec. = 0. 008, and requiring a conservative 1. 0 matching
radius, we find unique, unsaturated, multi-band S-COSMOS identifications for 3618 WISE sources.
Most of the WISE sources lacking S-COSMOS counterparts are from outside the S-COSMOS FoV.
9. –9–
Within the area of good, unique matches, 4% of WISE sources do not have S-COSMOS counterparts
′′
and < 1% of WISE sources have multiple S-COSMOS counterparts within the 1. 0 matching radius.
Visual inspection shows that confusion is the source of both of these issues, with the lower resolution
WISE images merging multiple objects. In the remainder of the paper, we restrict the analysis
to the ∼ 95% of WISE sources within the S-COSMOS area with unique, unsaturated multi-band
IRAC identifications.
Fig. 3 shows the measured differences between the WISE and S-COSMOS photometry. For S-
′′
COSMOS, we use aperture-corrected 2. 9 photometry from the public June 2007 catalog, converted
from physical units to Vega magnitudes using conversion factors prescribed by the S-COSMOS doc-
umentation available through the Infrared Science Archive (IRSA). As expected given the slightly
different central wavelengths and widths of the IRAC and WISE filters, we find slight median offsets
between their respective photometric measurements: (W 1−[3.6])med = −0.01 and (W 2−[4.5])med =
−0.07. The Explanatory Supplement to the WISE All-Sky Data Release12 finds a color term from
analysis of compact sources in the Spitzer SWIRE XMM-LSS field, (W 1 − [3.6]) ∼ 0.4([3.6] − [4.5])
(see Fig. 2 of §VI.3.a of the Explanatory Supplement).
2.2. Mid-Infrared Selection of AGN with Spitzer
Fig. 4 shows the IRAC color-color diagram for S-COSMOS sources with robust WISE coun-
terparts. The figure shows the expected concentration of Galactic stars with Vega colors of zero.
As discussed in Stern et al. (2007) and Eisenhardt et al. (2010), stars warmer than spectral class
T3 all have essentially Rayleigh-Jeans continua in the IRAC passbands, leading to similar IRAC
colors. Methane absorption causes redder [3.6]−[4.5] colors for cooler brown dwarfs, leading to a
vertical extension above the Galactic star locus. Few such sources are found by WISE over an
area as small as COSMOS. The sources extending to the right of the stellar locus is dominated by
low-redshift star-forming galaxies, where polycyclic aromatic hydrocarbon (PAH) emission causes
red [5.8]−[8.0] colors. Finally, as suggested in Eisenhardt et al. (2004) and discussed in detail in
Stern et al. (2005), the vertical extension perpendicular to the galaxy sequence is dominated by
AGN. Indeed, Gorjian et al. (2008) show that the majority (65%) of X-ray sources in the XBo¨tes o
survey are identified by the Stern et al. (2005) mid-infrared criteria (see also Donley et al. 2007;
Eckart et al. 2010; Assef et al. 2011). In IRAC data plotted to deeper depths, a highly populated
second vertical sequence is also visible to the left of the AGN sequence. This sequence, due to mas-
sive galaxies at z > 1.2 (e.g., Stern et al. 2005; Eisenhardt et al. 2008; Papovich 2008), typically
∼
outnumbers the AGN sequence since even very shallow (< 90 sec) IRAC pointings easily reach well
below the characteristic brightness of early-type galaxies out to z ∼ 2, m∗ ≈ 17.5 and m4.5 ≈ 16.7
3.6
∗
(e.g., Mancone et al. 2010). However, these galaxies are absent with our conservative, W 2 < 15 ∼
magnitude cut in the much shallower WISE data.
12
See http://wise2.ipac.caltech.edu/docs/release/allsky/expsup/index.html.
10. – 10 –
Fig. 4.— IRAC color-color diagram of WISE-selected sources in the COSMOS field. We only plot
sources with SN R ≥ 10 in W 1 and W 2, and we require [3.6] > 11 to avoid saturated stars. Sources
with W 1 − W 2 ≥ 0.8 are indicated with larger circles; filled circles indicate sources that were also
identified as AGN using the Stern et al. (2005) mid-infrared color criteria. Sources identified as
AGN using Spitzer criteria but not using the WISE criterion are indicated with exes.
In the following analysis we will adopt the Stern et al. (2005) mid-infrared AGN sample as the
‘truth sample’ in order to explore potential WISE AGN selection criteria. The Stern et al. (2005)
method for selecting AGN was one of the first methods devised to identify AGN using Spitzer
data and has been extensively used by other workers in the field. However, like all AGN selection
criteria, it is not without some shortcomings, highlighted below.
X-ray selected AGN missed by mid-infrared selection: As pointed out by numerous authors
(e.g., Barmby et al. 2006; Cardamone et al. 2008; Brusa et al. 2009), many X-ray sources have
mid-infrared colors consistent with normal galaxies, and thus are missed by the mid-infrared AGN
color criteria. As first pointed out by Donley et al. (2007) and further expanded upon by Eckart
et al. (2010), the fraction of X-ray sources identified as mid-infrared AGN increases strongly with
11. – 11 –
X-ray luminosity. For example, Donley et al. (2007), using data from the Ms Chandra Deep Field-
North (Alexander et al. 2003), find that the mid-infrared selection efficiency increases from ∼ 14%
at L0.5−8 keV < 1042 erg s−1 to 100% at L0.5−8 keV > 1044 erg s−1 . So while low-luminosity AGN are,
unsurprisingly, missed by the mid-infrared color selection criteria (e.g., Figs. 1 and 2), such criteria
appear remarkably robust at identifying the most luminous AGN in the universe.
Contamination by star-forming galaxies: Several authors have also pointed out that the mid-
infrared color cuts proposed by Lacy et al. (2004) and Stern et al. (2005) extend into regions of
color space populated by star-forming galaxies (e.g., Barmby et al. 2006; Donley et al. 2008; Park
et al. 2010). In order to minimize such contamination, mid-infrared power-law selection has been
suggested (e.g., Alonso-Herrero et al. 2006), though Donley et al. (2012) notes that systematic
photometric errors from IRAC are often underestimated (e.g., Reach et al. 2005), making power-
law selection more vulnerable to the quality of the mid-infrared photometry than simple color-color
cuts. Donley et al. (2012) investigates contamination by star-forming galaxies using a combination
of galaxy templates and real data from pure starbursts identified from Spitzer IRS spectroscopy. A
strong conclusion from this work is that mid-infrared color selection, particularly using the Stern
et al. (2005) criteria, has minimal contamination from purely star-forming galaxies below a redshift
of z ∼ 1.
Contamination by high-redshift galaxies: The Lacy et al. (2004) and Stern et al. (2005) criteria
for identifying AGN based on their mid-infrared colors were empirically derived from shallow,
wide-area Spitzer data. In this limit, the criteria work extremely well. In deeper mid-infrared
data, however, significant contamination from faint, high-redshift galaxies becomes problematic
and we recommend use of the revised IRAC selection criteria of Donley et al. (2012) for deep IRAC
data.
Completeness vs. reliability: Finally, in choosing between the IRAC color criteria of Lacy
et al. (2004) and Stern et al. (2005), we have opted for the latter. As pointed out by numerous
authors (e.g., Eckart et al. 2010; Donley et al. 2012), the less selective Lacy et al. (2004) criteria
have higher completeness at the cost of reliability: many more normal galaxies are identified using
those criteria, yielding more significant contamination. With the primary goal of identifying a clean
sample of powerful AGN, we therefore adopt the higher reliability IRAC color criteria of Stern et al.
(2005).
In summary, we adopt the Stern et al. (2005) mid-infrared-selected AGN candidates as the
‘truth sample’ for analyzing WISE selection of AGN. Foremost, identifying a robust truth sample
identified at similar wavelength makes logical sense. Radio selection would miss ∼ 90% of AGN,
while optical and X-ray selection would miss the heavily obscured AGN which are identified by
mid-infrared selection but largely missed by the current generation of optical and X-ray surveys. In
principle, a hybrid selection could be adopted, such as identifying all AGN candidates with LAGN
greater than some value. However, a ‘truth sample’ identified in that manner would be vulnerable
to spectroscopic incompleteness.
12. – 12 –
Despite these caveats to mid-infrared selection, we show that the Stern et al. (2005) criteria
are quite robust at the shallow mid-infrared depths of WISE. This method identifies the most lu-
minous X-ray-selected AGN at high completeness. It also identifies a much higher surface density
of AGN than optical and X-ray surveys of comparable depth due to an increased sensitivity to
obscured AGN. Illustrating this point, Hickox et al. (2007) and Eckart et al. (2010) show that
mid-infrared AGN candidates individually undetected at high energy are well detected in stacking
analyses and reveal a harder-than-average X-ray spectrum, implying significant obscuration. Opti-
cal spectroscopy of IRAC-selected AGN candidates also typically reveal type 2 AGN spectra (Stern
et al., in prep.). Finally, in shallow mid-infrared data, particularly at the depth of WISE, the Stern
et al. (2005) criteria suffer from minimal contamination by Galactic stars, starburst galaxies, or
high-redshift galaxies.
2.3. Mid-Infrared Selection of AGN with WISE
Fig. 5 shows a hybrid mid-infrared color-color diagram. Rather than plotting IRAC [3.6]−[4.5]
color along the vertical axis, we plot W 1 − W 2. We see similar trends to the IRAC-only diagram
(Fig. 4), with a stellar locus at zero color, a horizontal sequence of low-redshift galaxies, and a
vertical AGN sequence perpendicular to the galactic sequence. While mid-infrared selection of
AGN in even very shallow Spitzer pointings required the longer wavelength IRAC passbands to
differentiate AGN from high-redshift (z > 1.3) massive galaxies, WISE is able to robustly identify
∼
AGN with just W 1 and W 2 (e.g., see Ashby et al. 2009; Assef et al. 2010; Eckart et al. 2010). Note
that these are the two most sensitive WISE passbands, with the highest source counts and the best
spatial resolution.
We have explored how robustly WISE identifies AGN using a simple W 1 − W 2 color cut.
Of the 3618 sources in our cross-matched WISE-S-COSMOS catalog, 157 are mid-infrared AGN
according to the Stern et al. (2005) criteria. We consider this the truth sample and Fig. 6 shows
the completeness and reliability of WISE AGN selection as a function of W 1 − W 2 color cut. Prior
to the launch of WISE, Ashby et al. (2009) suggested W 1 − W 2 ≥ 0.5 would robustly identify AGN
while Assef et al. (2010) suggested a color cut of W 1 − W 2 ≥ 0.85. Considering the former, while
this criterion is highly (98%) complete at identifying the AGN sample, it suffers from significant
contamination from non-active sources (see Fig. 6; only 50% of sources appear active according to
the IRAC criteria). This is likely, in part, due to the significantly better performance of WISE
compared to the prelaunch predictions: Mainzer et al. (2005) reported 5σ point source sensitivity
requirements of 120 µJy at 3.4 µm and 160 µJy at 4.6 µm, while we are finding 10σ point source
sensitivities of 70 µJy at 3.4 µm and 160 µJy at 4.6 µm. Analysis of Fig. 6 suggests a color cut
at W 1 − W 2 = 0.8 offers an extremely robust AGN sample which is still highly complete. For
some uses, a slightly less conservative color cut at W 1 − W 2 = 0.7 might be preferable, providing
a powerful compromise between completeness and reliability for WISE AGN selection.
Using W 1 − W 2 ≥ 0.8 to select AGN candidates, we identify 130 potential candidates, of
13. – 13 –
Fig. 5.— Mid-infrared color-color diagram of WISE-selected sources in the COSMOS field, with
WISE W 1 − W 2 plotted against IRAC [5.8] − [8.0]. Symbols are as in the previous figure.
which 123 are AGN according to their IRAC colors (95% reliability, 78% completeness). The less
conservative color cut at W 1− W 2 ≥ 0.7 identifies 160 candidates, of which 136 are AGN according
to their IRAC colors (85% reliability, 87% completeness) — e.g., this less restrictive color cut
identifies ∼ 10% more AGN at the cost of tripling the number of contaminants. As seen in Fig. 4,
several of the “mis-identified” AGN candidates have colors very close to the Stern et al. (2005)
criteria. In fact, as discussed in § 3.7, four of the seven “contaminants” for the W 1 − W 2 ≥ 0.8
AGN selection have spectroscopic redshifts, two of which are broad-lined quasars. This implies
that the above reliability numbers are likely conservative, though complete spectroscopy will be
required to determine what fraction of the IRAC-selected AGN are, in fact, not active. As seen
in Fig. 5, mis-identified AGN candidates often have much redder [5.8] − [8.0] colors, suggestive
of low-redshift galaxies with PAH emission. Potential Galactic contaminants are brown dwarfs
(cooler than spectral class T3) and asymptotic giant branch (AGB) stars, both of which have much
lower surface densities than AGN at the depths probed and are not expected to be a significant
14. – 14 –
Fig. 6.— Reliability (solid line) and completeness (dotted line) of WISE AGN selection as a
function of a simple W 1 − W 2 color selection. Blue cuts have very high completeness — e.g.,
select all sources which are identified as mid-infrared AGN candidates according to the Stern et
al. (2005) IRAC criteria. However, blue cuts have poor reliability, selecting many sources whose
mid-infrared colors suggest they are normal galaxies. Likewise, red cuts robustly select AGN with
few contaminants, but have low completeness. Using the criteria W 1 − W 2 ≥ 0.8 offers both high
completeness (78%) and high reliability (95%).
contaminant, particularly in extragalactic pointings.
In the following section we use the extensive publicly available data in the COSMOS field to
explore the demographics, multiwavelength properties and redshift distribution of WISE-selected
AGN using the simple W 1 − W 2 ≥ 0.8 color criterion.
15. – 15 –
3. Properties of WISE AGN
3.1. Demographics of WISE AGN
The effective area of the S-COSMOS survey is 2.3 deg2 per passband after removal of poor
quality regions around saturated stars and the field boundary (Sanders et al. 2007). Since approxi-
mately 8% of the field is only covered by two of the four IRAC passbands, this implies a four-band
effective area of approximately 2.1 deg2 . Our simple W 1 − W 2 color criterion identified 130 AGN
candidates in this area, implying a surface density of 61.9 ± 5.4 WISE-selected AGN candidates
per deg2 , 5% of which are expected to be contaminants.
For comparison, the Sloan Digital Sky Survey (SDSS) quasar selection algorithm (Richards
et al. 2002) targeted ultraviolet excess quasars to i∗ = 19.1 (AB mag; 13.0 targets per deg2 )
and higher redshift (z > 3) quasars to i∗ = 20.2 (AB mag; 7.7 targets per deg2 ), yielding a
∼
combined list of 18.7 candidates per deg2 . These depths are comparable to WISE depths for type 1
quasar selection (e.g., Assef et al. 2010). The SDSS algorithm is expected to provide over 90%
completeness from simulated type 1 quasar spectra, although at the cost of lower reliability. The
overall efficiency (quasars / quasar candidates) was only 66% from initial test data over 100 deg2 ,
with the contaminants evenly split between galaxies and Galactic stars. Importantly, optical/UV
quasar selection methods are hampered at certain redshifts, especially high ones, where the stellar
locus overlaps the quasar locus in color-color space. More sophisticated approaches, such as that
presented in Bovy et al. (2011), work better than the old two-color or three-color cuts, though
they still have issues. Other methods, such as variability (e.g., Palanque-Delabrouille et al. 2011),
also do better, but require more elaborate input data sets. WISE selection is less affected by
these problems, and has a much flatter selection function as a function of redshift than traditional
color-selected UV-excess methods. In particular, our simple W 1 − W 2 selection is expected to have
78% completeness and 95% reliability assuming that the Stern et al. (2005) mid-infrared selection
of AGN candidates from the deeper S-COSMOS data is 100% reliable.
3.2. Mid-Infrared Properties of WISE AGN
We have studied the longer wavelength properties of WISE-selected AGN with an eye towards
investigating whether the inclusion of W 3 or W 4 would allow for a more robust WISE selection of
AGN, such as the wedge in W 1 − W 2 vs. W 2 − W 3 color-color space presented in Jarrett et al.
(2011). Our simple W 1 − W 2 color criterion identified 130 AGN candidates in COSMOS, of which
24 (18%) are detected in W 3 (≥ 10σ) and only 3 (2%) are detected in W 4 (≥ 10σ). If we instead
use a less conservative 5σ detection threshold, we find that 78 (60%) are detected in W 3 and 17
(13%) are detected in W 4. These percentages are essentially unchanged when we consider the 123
robust AGN candidates identified by both the WISE and IRAC selection criteria: 24 (20%) are
detected in W 3 (≥ 10σ) and 3 (2%) are detected in W 4 (≥ 10σ). Using the 5σ detection threshold,
16. – 16 –
these numbers increase to 74 (60%) being detected in W 3 and 17 (14%) being detected detected in
W 4.
This implies that including the longer wavelength WISE data increases the reliability of the
AGN selection, but at the cost of a significant decrease in completeness. For example, requiring
a 10σ detection in W 3 in addition to the W 1 − W 2 color criterion provides a surface density of
only 11 WISE-selected AGN candidates per deg2 , but the reliability is expected to be ∼ 100%.
Using the less conservative requirement of a 5σ detection in W 3 provides a surface density of 37
WISE-selected AGN candidates per deg2 with a reliability of 95% – e.g., the same reliability as
our original W 1 − W 2 ≥ 0.8 color cut. Any of these mid-infrared selection criteria compare quite
favorably with the SDSS quasar selection in terms of surface density, completeness and reliability.
However, in what follows we rely on selecting AGN using only the single W 1 − W 2 ≥ 0.8 color
criterion, as this selection, relying on the most sensitive WISE passbands, identifies a much larger
candidate AGN population, 2 to 5 times larger than the samples that also require W 3 detections.
Finally, we note that the depth of the WISE survey varies strongly with ecliptic latitude. The
COSMOS field was selected to be at low ecliptic latitude in order to make it accessible from both
hemispheres, and thus is close to the minimum depth of the WISE survey with a coverage of 12
frames (11 sec each). Higher latitude fields have deeper data, reaching a coverage of 250 frames at
the ecliptic poles (Jarrett et al. 2011). This increases the surface density of AGN candidates, but
with a decrease in robustness since deeper pointings will detect massive galaxies at z > 1 which
∼
have similar W 1 − W 2 colors to AGN. The inclusion of the deeper W 3 data in such fields could
be used to separate normal galaxies from AGN. WISE selection of AGN in deeper, higher latitude
fields is addressed more thoroughly in Assef et al. (2012).
3.3. X-Ray Properties of WISE AGN
The COSMOS field has been observed by both the Chandra X-Ray Observatory (Elvis et al.
2009) and XMM-Newton (Hasinger et al. 2007). In the following two subsections, we examine the
X-ray properties of WISE-selected AGN using each of these surveys.
3.3.1. Chandra Observations
The Chandra-COSMOS Survey (C-COSMOS; Elvis et al. 2009) is a large, 1.8 Ms, Chandra
program that imaged the central 0.5 deg2 of the COSMOS field with an effective exposure time of
160 ks per position and the outer 0.4 deg2 with an effective exposure time of 80 ks per position. The
corresponding point source depths in the deeper portion of the survey are 1.9 × 10−16 ergs cm−2 s−1
in the soft (0.5 − 2 keV) band, 7.3 × 10−16 ergs cm−2 s−1 in the hard (2 − 10 keV) band and
5.7 × 10−16 ergs cm−2 s−1 in the full (0.5 − 10 keV) band, where these depths assume an average
X-ray power law index Γ = 1.4. C-COSMOS detected 1761 reliable X-ray point sources (catalog
17. – 17 –
Fig. 7.— Mid-infrared color-color diagram of WISE-selected sources in the COSMOS field, with
WISE W 1 − W 2 plotted against IRAC [5.8] − [8.0]. Many of the WISE sources lacking Chandra
counterparts are from outside the field-of-view of the C-COSMOS survey.
ver.2.1; spurious probability < 2 × 10−5 ). We use a 2. 5 matching radius to cross-identify the WISE
′′
and Chandra sources.
A total of 167 of the Chandra X-ray sources have WISE counterparts (Fig. 7). Most have
relatively blue W 1 − W 2 colors and are likely associated with low-redshift galaxies harboring low-
luminosity AGNs; such sources are common in deep X-ray observations (e.g., Brandt & Hasinger
2005). A concentration of X-ray sources near zero mid-infrared colors are predominantly low-
redshift (z < 0.6) early-type galaxies: such galaxies have little or no star formation and therefore
∼
lack the dust and PAH emission which causes a horizontal extension in this mid-infrared color-color
space. Finally, deep Chandra surveys are also sensitive to X-ray emission from low-mass Galactic
stars, which likewise reside in this same region of color-color space (e.g., Stern et al. 2002a).
More interesting is the vertical extension seen in Fig. 7: 41 of the WISE-selected AGN candi-
dates have C-COSMOS counterparts. Most of the WISE+IRAC AGN candidates lacking Chandra
18. – 18 –
counterparts in Fig. 7 are from outside the C-COSMOS FoV. Six (e.g., 13%) of the WISE-selected
AGN candidates whose IRAC colors are consistent with the Stern et al. (2005) AGN selection
criteria were observed by, but not detected by Chandra. We list these sources in Table 1. All are
at least 9′′ from the nearest Chandra source. These mid-infrared sources are strong candidates for
Compton-thick AGN (e.g., NH ≥ 1024 cm−2 ): sources with so much internal absorption that their
X-ray emission below 10 keV is heavily absorbed, undetected in the ∼ 100 ks Chandra observa-
tions. The absorbing material, however, is heated up and is easily detected in ∼ 100 s integrations
with WISE. We also note, as expected, that the small number of WISE AGN contaminants with
W 1−W 2 ≥ 0.8 but whose IRAC colors are not consistent with an AGN are undetected by Chandra.
Fig. 8 shows the relationship between hard X-ray (2 − 10 keV) fluxes of S-COSMOS sources
and their hardness ratios HR ≡ (H − S)/(H + S), where H and S are the numbers of hard and
soft X-ray photons detected, respectively. We compare the full sample (smallest black dots) to
the subset with WISE counterparts (small black circles) to the smaller set of sources with IRAC
and/or WISE colors indicative of AGN activity (larger symbols). Note that many of the brightest
X-ray sources in the field are identified as AGN candidates by WISE, regardless of their hardness
ratio.
3.3.2. XMM-Newton Observations
The XMM-Newton wide-field survey of the COSMOS field (XMM-COSMOS; Hasinger et al.
2007; Brusa et al. 2010) observed the entire 2 deg2 COSMOS field to medium depth (∼ 60 ks). The
survey detected nearly 2000 X-ray sources down to limiting fluxes of ∼ 5×10−16 ergs cm−2 s−1 in the
0.5 − 2 keV (soft) band and ∼ 3 × 10−15 ergs cm−2 s−1 in the 2 − 10 keV (hard) band. Thus, XMM-
COSMOS covers a wider area than C-COSMOS, albeit to shallower depth. We use the November
2008 XMM-Newton point-like source catalog, available thru IRSA, which contains 1887 sources.
Table 1. WISE+IRAC AGN candidates undetected by Chandra.
WISE ID i W1 W2 W1 − W2 [5.8]−[8.0] z Notes
J095855.40+022037.4 19.43 15.41 14.59 0.82 1.39 [0.38] bright galaxy
J095937.35+021905.9 22.30 16.00 14.70 1.30 1.17 0.927
J100006.19+015535.3 20.90 15.53 14.19 1.34 1.05 0.661
J100043.70+014202.5 21.77 15.89 14.89 1.00 1.40 0.741
J100046.91+020726.5 21.86 14.87 13.14 1.73 1.18 1.158 faint
J100135.61+022104.8 25.11 16.98 14.97 2.01 1.49 ··· faint
Note. — Bracketed redshift indicates photometric redshift.
19. – 19 –
Fig. 8.— X-ray hardness ratio HR ≡ (H − S)/(H + S), where H (S) is the number of detected
hard (soft) X-ray counts, plotted against hard X-ray flux. All X-ray data is from Chandra; at
the depth of these data, most X-ray sources are expected to be AGN. We identify no Chandra
counterparts for the WISE-selected AGN candidates whose IRAC colors are indicative of being
normal, non-active galaxies. Note that many (but not all) of the brightest hard X-ray sources are
identified as AGN candidates by both WISE and IRAC.
′′
Using a 3. 5 matching radius — slightly larger than used for C-COSMOS to account for the poorer
spatial resolution of XMM-Newton — we identify WISE counterparts for 244 XMM-COSMOS
sources, of which 92 have W 1 − W 2 ≥ 0.8. The mid-infrared color distribution of XMM sources is
similar to what was seen for C-COSMOS, though more of the mid-infrared AGN candidates have
X-ray detections courtesy of the wider spatial coverage of this survey (Fig. 9). Thirty-three WISE
sources whose IRAC colors suggest an active nucleus (out of 123) are undetected by XMM-Newton,
though seven are from outside the XMM-Newton coverage; the other 26 are listed in Table 2. All
six of the sources from Table 1 remain undetected by XMM-Newton.
Therefore, 75% of the WISE-selected AGN candidates have XMM-Newton counterparts, but
20. – 20 –
Fig. 9.— Mid-infrared color-color diagram of WISE-selected sources in the COSMOS field, with
WISE W 1 − W 2 plotted against IRAC [5.8] − [8.0]. Dots show all WISE sources in the field, larger
filled circles show WISE sources with XMM counterparts.
that still leaves a significant number of WISE-selected AGN — including those whose IRAC colors
indicate an AGN — that are undetected by XMM-Newton. We also note that two of the sources
with W 1 − W 2 ≥ 0.8 but outside of the Stern et al. (2005) IRAC wedge are detected in the X-rays;
both have IRAC colors very close to the wedge defined in that paper.
Similar to the Chandra results, we find that the WISE-selected AGN are brighter and have
softer spectra than typical XMM-Newton sources in XMM-COSMOS. However, Fig. 10 also shows
quite clearly that the brightest X-ray sources tend to be identified as AGN candidates from their
WISE colors, regardless of X-ray hardness ratio. For comparison, we also plot the expected point
source sensitivity of the all-sky eROSITA telescope. The brightest soft X-ray sources, F0.5−2keV >∼
2 × 10−14 erg cm−2 s−1 , will basically all already have been identified as AGN candidates by WISE.
At the sensitivity limit of eROSITA, however, large numbers of X-ray sources are expected that are
not identified by WISE; these are likely lower luminosity AGN at lower redshifts (e.g., Eckart et al.
21. – 21 –
Fig. 10.— X-ray hardness ratio HR from XMM-Newton plotted against X-ray flux (right: soft-
band, 0.5 − 2 keV; left: hard-band, 2 − 10 keV). Note that many (but not all) of the brightest hard
X-ray sources are identified as AGN candidates by both the WISE criterion and by their IRAC
colors (large black circles). The vertical dashed line in the left panel shows the expected soft-band
point source sensitivity of the all-sky eROSITA survey; the hard-band point source sensitivity
corresponds approximately to the right-hand axis of the high-energy panel. While the brightest
soft X-ray sources are expected to also be identified by eROSITA, many WISE-selected AGN
candidates are below the eROSITA flux limits. Conversely, eROSITA is expected to identify many
lower luminosity AGN that are not identified as AGN candidates by WISE.
2010; Donley et al. 2012). WISE also detects a significant population of fainter, harder spectrum X-
ray sources, below the sensitivity limit of eROSITA. These results, particularly Fig. 10, emphasizes
the complementarity of X-ray and mid-infrared AGN selection: each selection technique identifies
samples of AGN missed by the other technique.
Finally, using the greater statistics of the XMM-Newton sample, we consider if there are any
trends between X-ray hardness ratio and mid-infrared W 1−W 2 color. Though no strong correlation
is evident, we do find the expected general trend of redder mid-infrared sources having harder X-
ray spectra. Splitting the X-ray sample at HR = 0, the softer mid-infrared AGN candidates (e.g.,
HR < 0) have a mean WISE color of W 1 − W 2 = 1.18. In contrast, the harder mid-infrared
AGN candidates (e.g., HR > 0) have a mean WISE color of W 1 − W 2 = 1.32. However, there
are examples of very hard X-ray sources with relatively blue WISE colors, as well as very soft X-ray
sources with relatively red WISE colors.
23. – 23 –
Fig. 11.— Mid-infrared color-color diagram of WISE-selected sources in the COSMOS field, with
WISE W 1 − W 2 plotted against IRAC [5.8] − [8.0]. Plotted sources and symbols are as in Fig. 5,
with large black circles added for all WISE sources with VLA counterparts in the VLA-COSMOS
survey.
3.4. Radio Properties of WISE AGN
The Very Large Array (VLA) obtained deep radio images of the COSMOS field at 20 cm. The
goals, observing strategy, and data reductions for this large program, called the VLA-COSMOS
survey, are described in Schinnerer et al. (2007). The survey entailed nearly 350 hr of exposure
time, primarily in the highest resolution, or A, configuration. The Large project imaged the full 2
deg2 COSMOS field with a resolution of 1. 5 to a sensitivity of ∼ 11µJy (1σ) (Bondi et al. 2008).
′′
We use the joint catalog of Schinnerer et al. (2010), which combines an improved analysis of the
Large project with data from the Deep project that doubled the integration time in the central 0.84
deg2 region of the survey. The Joint catalog includes 2865 sources, of which 131 consist of multiple
components.
24. – 24 –
We match the full Joint catalog to the full WISE source list of 3618 sources using a 1. 5 ′′
matching radius. We find 333 matches, of which 33 have multiple components in the VLA data.
Fig. 11 shows the mid-infrared colors of the VLA sources, which shows many radio-detected sources
on both sides of our W 1 − W 2 = 0.8 color cut. This is unsurprising, as these extremely deep radio
data detect emission related to stellar processes (e.g., supernova remnants) as well as AGN activity
at a range of Eddington ratios. Considering the WISE-selected AGN candidates, 55 of the 130
candidates (42%) have radio matches; five of these are flagged as consisting of multiple components
in the radio data. Of the 123 AGN candidates identified by both WISE and IRAC, 52 (42%) are
detected by these very deep radio data. For the WISE-selected AGN not flagged as likely AGN by
IRAC, three (43%) are detected by the VLA. All of these fractions are much higher than the 8%
of sources with W 1 − W 2 < 0.8 which are detected by the VLA-COSMOS survey.
Assuming a typical quasar radio spectral index α = −0.5 (Sν ∝ ν α ) and adopting the Gregg
et al. (1996) cutoff value for the 1.4 GHz specific luminosity, L1.4GHz = 1032.5 h−2 erg s−1 Hz−1
50
(≈ 1024 h−2 W Hz−1 sr−1 ), to discriminate radio-loud and AGN radio-quiet populations, only two of
50
98 the WISE-selected AGN with spectroscopic redshifts are radio-loud13 . The results are unchanged
if we assume α = −0.8, as might be more typical for quasars without the jet aligned along our line
of sight. Both of these sources are SDSS quasars at z > 1 (WISE J095821.65+024628.2 at z = 1.405
and WISE J095908.32+024309.6 at z = 1.318). These two sources come from a total of 45 WISE-
selected AGN that are optically bright and have spectroscopy from the SDSS; all are classified as
broad-lined, and 35 are at z > 1 implying that they are clearly luminous quasars. Considering
just this SDSS subsample of WISE-selected AGN, our results are statistically consistent with the
canonical value of ∼ 10% of quasars being radio-loud (e.g., Stern et al. 2000b). However, the fact
that none of the 53 other sources with spectroscopic redshifts are radio-loud is surprising, suggesting
that the radio-loud fraction might be different for type 2 AGN. We note, however, that Zakamska
et al. (2004) found no change in the radio-loud fraction for their sample of SDSS-selected obscured
quasars.
Note that radio-loud AGN do not fall below the 5σ VLA-COSMOS sensitivity until beyond
z ∼ 10; e.g., the survey is sensitive enough to detect all radio-loud AGN that WISE is likely to
detect. All of the WISE-selected AGN candidates without redshifts that were detected by the
VLA-COSMOS survey have Sν < 0.72 mJy, implying that they would have to be at z > 3.4 in
order to be radio-loud.
13
For consistency with previous work in terms of defining the boundary between radio-loud and radio-quiet popu-
lations, 1.4 GHz specific luminosity is calculated for an Einstein-de Sitter cosmology; e.g., see Stern et al. (2000b).
25. – 25 –
Fig. 12.— Histograms of SDSS r-band (left) and Subaru r + -band (right) optical magnitudes of all
WISE-selected sources in the COSMOS field (open histogram). Solid histograms show distributions
for WISE-selected AGN candidates. Dotted lines show the fraction of WISE sources that are AGN
candidates as a function of optical magnitude (in 0.5 mag bins). While very few sources brighter
than ∼ 19th mag are AGN candidates, the fraction increases to > 50% at the faintest magnitudes.
3.5. Optical Magnitudes and Colors of WISE AGN
We next consider the optical properties of the WISE-selected AGN candidates. Fig. 12 shows
the r-band magnitude distributions of all WISE sources in the COSMOS field (open histogram) as
well as the AGN candidates with W 1 − W 2 ≥ 0.8 (solid histogram). All photometry is in the AB
system and comes from the COSMOS photometry catalog of Capak et al. (2007), which is available
through IRSA. The left panel shows r-band photometry from the second data release (DR2) of
the SDSS (Abazajian et al. 2004). Objects as bright as 10th mag have good photometry in the
SDSS imaging, and the imaging depth, defined as the 95% completeness limit for point sources,
is r ∼ 22.2. Similar data is available over more than 11,000 deg2 . However, many of the WISE
sources are fainter than this limiting depth, so in the right panel of Fig. 12 we show the Subaru r +
photometry in the COSMOS field obtained with the Suprime-Cam instrument (Komiyama et al.
2003). These data reach a 5σ depth (3′′ aperture) of 26.6 and detect all of the WISE-selected AGN
26. – 26 –
Fig. 13.— Distribution of r-band magnitudes for WISE-selected AGN candidates identified over
4000 deg2 of the SDSS.
candidates. Many of the brighter sources in the Subaru data are unresolved, leading to saturation
issues. This causes the truncation seen at r + < 18.
∼
Fig. 12 shows that very few of the WISE-selected AGN candidates are brighter than r ∼ 18,
and they represent less than 5% of the WISE source population at bright optical magnitudes.
However, the AGN candidates represent an increasing fraction of the optically fainter WISE sources,
accounting for ∼ 20% of WISE sources at r ∼ 21 and more than 50% of WISE sources with r > 23. ∼
In order to explore the optical brightnesses of WISE-selected AGN candidates with higher fidelity,
we identified AGN candidates over 4000 deg2 of the SDSS (c.f., Donoso et al. 2012; Yan et al. 2012).
Fig. 13 shows the resultant r-band distribution. While the majority of AGN candidates are well
detected in the SDSS imaging, their optical brightness distribution peaks at r ∼ 19.5, making them
fainter than the typical spectroscopic limits of SDSS, i ∼ 19.1 for quasars and r ∼ 17.8 for galaxies
(as discussed in the following section, approximately half of our WISE-selected AGN candidates
are spatially resolved).
27. – 27 –
Fig. 14.— Optical color-magnitude diagram of WISE sources in the COSMOS field. Optical
photometry is from SDSS, and symbols are indicated in the upper left. WISE-selected AGN
candidates tend to optical colors that are bluer than typical field sources, though a significant
fraction of the AGN candidates overlap with the field population.
Fig. 14 shows an optical color-magnitude diagram of WISE sources. At bright magnitudes, the
distribution is dominated by Galactic stars with r−i ∼ 0.1, while a second galaxy sequence becomes
evident at r > 18. Mid-infrared AGN candidates are, on average, bluer than typical galaxies,
∼
though the color distribution clearly overlaps with the galaxy sample. AGN candidates identified
by both WISE and Spitzer/IRAC, which represent the most robust AGN sample with the highest
rate of X-ray detections, tend to be bluer than galaxies at i < 21, though at fainter magnitudes
∼
where obscured AGN become more prevalent, the distribution fans out. This is partially due to
photometric errors, but also because a large fraction of the AGN candidates have colors similar to
galaxies. Not surprisingly, AGN candidates identified by Spitzer but not by WISE— e.g., sources
at the blue corner of the Stern et al. (2005) wedge and close to the galaxy locus in mid-infrared
color-color space — tend to have galaxy-like optical colors.
28. – 28 –
(a) (b)
WISE J095834.75+014502.4 WISE J100109.17+022254.3
(c) (d)
WISE J100005.98+015453.1 WISE J100049.63+014048.6
Fig. 15.— Hubble/ACS I814 images of four WISE-selected AGN in the COSMOS field, showing
the range of optical morphologies. Approximately half of the sources are unresolved point sources
(e.g., panel a). The other half are spatially resolved (e.g., panels b-d), sometimes with rather faint
optical magnitudes. All four sources shown here are identified as candidate AGN by both WISE
and IRAC color criteria. Images are ∼ 4′′ on a side (e.g., smaller than the WISE PSF), with North
up and East to the left.
3.6. Morphologies of WISE AGN
Conventional wisdom states that the most luminous AGN in the universe are associated with
unresolved point sources at optical wavelengths. While this is true for the vast majority of unob-
scured, type 1 quasars, this is not the case for obscured, type 2 quasars. For instance, luminous
high-redshift radio galaxies often have a clumpy, irregular morphology at rest-frame ultraviolet
wavelengths, with the emission generally elongated and aligned with the radio source axis (e.g.,
McCarthy et al. 1987). At rest-frame optical wavelengths, where stars dominate the galaxy lumi-
nosity, the hosts of most luminous radio galaxies are normal elliptical galaxies with r 1/4 -law light
29. – 29 –
profiles (e.g., Zirm et al. 2003).
The cornerstone data set for the COSMOS survey is its wide-field Hubble Space Telescope
Advanced Camera for Surveys (ACS) imaging (Scoville et al. 2007; Koekemoer et al. 2007). With
583 single-orbit F814W (I814 hereafter) observations, these data cover (or define) the 1.8 deg2
COSMOS field and constitute the largest contiguous Hubble imaging survey to date. The data
′′
are extremely sensitive, with 0. 09 resolution (FWHM) and reaching a 50% completeness limit of
′′ 5 in diameter.
I814 = 26.0 (AB) for sources 0.
Griffith & Stern (2010) have recently analyzed the optical morphologies of AGN in the COS-
MOS field identified from a variety of methods: radio selection, X-ray selection, and mid-infrared
selection (see also Gabor et al. 2009). They find that the radio-selected AGN are likely to be hosted
by early-type galaxies, while X-ray and mid-infrared selected AGN are more often associated with
point sources and disk galaxies. Considering just the brighter X-ray and mid-infrared subsamples,
approximately half of the AGN are optically unresolved and a third are associated with disk galax-
ies. These morphological results conform with the results of Hickox et al. (2009) who studied the
colors and large-scale clustering of AGN, and found a general association of radio-selected AGN
with “red sequence” galaxies (an old, well-known result; e.g., Matthews et al. 1964), mid-infrared
selected AGN are associated with “blue cloud” galaxies, and X-ray selected AGN straddle these
samples in the “green valley”.
We find similar results here. Of the 130 WISE-selected AGN candidates, 94 are located within
the portion of COSMOS imaged by ACS. A bit more than half (52/94, or 55%) of the sources are
spatially resolved; the other AGN candidates are associated with point sources. As an aside, we
note that one of the contaminants, WISE J100050.63+024901.7 was flagged by Faure et al. (2008)
as one of the 20 most likely strong lensing systems in the COSMOS field (see also Jackson 2008).
The ACS I814 image of this system shows four faint arcs surrounding a bright early-type galaxy,
′′
with a radial separation of 1. 9. Inspection of the IRAC images for this system shows that the
mid-infrared data are still dominated by the optically bright lensing galaxy.
Fig. 15 shows Hubble/ACS I814 images of four example WISE-selected AGN. All four examples
were also identified as AGN candidates by their IRAC colors. Several are X-ray and/or radio
sources as well. Panel (a) shows WISE J095834.75+014502.4, a bright SDSS quasar at z = 1.889.
It is unresolved in the ACS image; approximately half of the WISE AGN candidates have similar
morphologies. Panel (b) shows WISE J100109.21+022254.2, one of the optically faintest WISE-
selected AGN candidates in the COSMOS field, with I814 = 22.9. As discussed in the next section,
we were unable to obtain a redshift for this source from deep Keck spectroscopy, though subsequent
to our observations, Brusa et al. (2010) reported that this source is as a narrow-lined AGN at
z = 1.582. Panels (c) and (d) show two z ∼ 0.9 type 2 (e.g., narrow-lined) AGN from Trump et al.
(2007). The former is WISE J100005.99+015453.3, which is a spiral galaxy with a very bright
nucleus. The latter is WISE J100013.42+021400.4, which has a more irregular morphology.
Fig. 16 presents a color-magnitude diagram of WISE sources in the COSMOS field, with
30. – 30 –
optical-to-mid-infrared color plotted against 4.6 µm brightness (W 2). For the AGN candidates,
we only plot the ∼ 70% of sources covered by the ACS imaging. There are several things to note
from this plot. First, the WISE-only AGN candidates (e.g., WISE-selected AGN candidates not
identified as AGN candidates from their Spitzer colors) clearly reside on the right side of Fig. 16,
with no contaminants brighter than W 2 = 14.8. This implies that caution should be applied before
extending our simple WISE color criterion to fainter limits. Indeed, in Assef et al. (2012) we
investigate the interloper fraction as a function of W 2 magnitude and derive a magnitude-dependent
WISE AGN selection criterion applicable to higher ecliptic latitude (e.g., deeper) portions of the
WISE survey.
Second, optically unresolved AGN candidates tend to have bluer r − W 2 colors, consistent
with the expectation that they suffer less extinction at optical wavelengths. Quantitatively, the
unresolved WISE+IRAC AGN candidates in Fig. 16 have r − W 2 = 5.18. Similarly selected
sources that are resolved in the Hubble imaging have r − W 2 = 7.29. The unresolved AGN
candidates are also slightly brighter, with W 2 = 14.54 as compared to W 2 = 14.69 for the
resolved WISE+IRAC AGN candidates. Importantly, however, we note that both resolved and
unresolved sources are found across the full W 2 range probed.
Finally, we also consider the optical properties of the WISE+IRAC AGN candidates that
are undetected by XMM-Newton (Table 2). These sources have an even fainter median mid-IR
brightness, W 2 = 14.72, and also have redder optical-to-mid-IR colors than typical WISE+IRAC
AGN candidates. Quantitatively, r − W 2 = 6.58 for the X-ray-undetected AGN candidates, while
r − W 2 = 5.85 for the X-ray detected WISE+IRAC AGN sample. This is consistent with the X-
ray undetected sources being associated with more heavily obscured AGN, diminishing both their
optical and X-ray fluxes.
3.7. Redshift Distribution of WISE AGN
In order to understand the redshift distribution and properties of WISE-selected AGN candi-
dates, we have both matched the candidate list to publically available spectroscopy in the COSMOS
field and obtained new observations. Published spectroscopy come from several papers: bright tar-
gets have spectroscopic redshifts from the SDSS (Abazajian et al. 2009); Prescott et al. (2006)
reports on MMT/Hectospec follow-up of optically selected quasar candidates in COSMOS; Lilly
et al. (2007) reports on zCOSMOS, a large VLT/VIMOS I-band magnitude-limited survey of the
COSMOS field; Trump et al. (2007) and Trump et al. (2009) report on Magellan/IMACS spec-
troscopy of X-ray- and radio-selected AGN candidates in the COSMOS field; and Brusa et al.
(2010) report on spectroscopy of X-ray sources from the XMM-Newton wide-field survey of the
COSMOS field, synthesizing both previously published results and new spectroscopy from Keck.
We obtained additional spectroscopy on UT 2010 March 12-15 using the Low Resolution
Imaging Spectrometer (LRIS; Oke et al. 1995) and the DEep Imaging Multi-Object Spectrograph
31. – 31 –
Fig. 16.— Optical-to-mid-infrared vs. mid-infrared color-magnitude diagram of WISE-selected
sources in the COSMOS field. Optical photometry is from SDSS, and symbols are indicated in the
upper left. Only those AGN candidates covered by the COSMOS Hubble images are plotted, and
they are flagged by their ACS morphologies.
(DEIMOS; Faber et al. 2003). We observed three Keck slitmasks in the COSMOS field. On UT
2010 March 12 we observed cos10b for 5200 s using the dual-beam LRIS instrument. We used
the 400 ℓ mm−1 grism on the blue arm of the spectrograph (blazed at 3400 ˚; resolving power
A
R ≡ λ/∆λ ∼ 600), the 400 ℓ mm −1 grating on the red arm of the spectrograph (blazed at 8500 ˚;
A
R ∼ 700) and 6800 A ˚ dichroic. On UT 2010 March 13 we observed cos10a for 1200 s using LRIS.
The red CCD was non-functional that night, so we channeled all of the light to the blue arm of
the spectrograph and again used the 400 ℓ mm−1 grism blazed at 3400 ˚. On UT 2010 March 14
A
we observed cos10d for 3600 s with DEIMOS in cloudy conditions, using the 600 ℓ mm−1 grating
(blazed at 7500 ˚; R ∼ 1600) and the 4000 ˚ order-blocking filter. Masks all used ∼ 1. 2 wide
A A ′′
slitlets. Data reduction followed standard procedures, and we flux calibrated the data using ob-
servations of standard stars from Massey & Gronwall (1990). Note that the DEIMOS data were
32. – 32 –
taken in non-photometric conditions, resulting in an uncertainty in the flux scale of those sources.
Target selection was done prior to access to the WISE data in the COSMOS field, though
we had already anticipated that red W 1 − W 2 colors would be an effective method to identify a
large population of AGN. We sought to test that hypothesis using Spitzer/IRAC imaging from the
S-COSMOS survey (Sanders et al. 2007), assuming that W 1 ∼ [3.6] and W 2 ∼ [4.5]. Additional
targets were selected using the Stern et al. (2005) IRAC AGN wedge selection criteria. Fig. 17 and
Table 3 present the results for the six COSMOS targets that subsequently were found to match our
W 1−W 2 ≥ 0.8 AGN candidate selection criterion. All six would also be selected by the Stern et al.
(2005) IRAC criteria. Table 4 in the Appendix presents the results for the additional COSMOS
targets observed on these masks. Our new Keck results are occasionally slightly discrepant with
previous results, but typically with ∆z ≤ 0.01. The signal-to-noise ratio of these new data are quite
high and the data were taken at relatively high spectral dispersion, suggesting that these redshifts
should take precedence over previous results.
Four of the sources show prominent AGN features, such as broadened Mg II 2800 emission.
WISE J100036.06+022830.5 does not show obvious AGN features; the spectrum shows narrow
emission lines from [O II], [Ne III], Hβ, and [O III], as well as Balmer absorption lines indicative of
a relatively young stellar population. We find log ([O III] / Hβ) ∼ 0.12, which is consistent with
both star-forming and AGN activity in the Baldwin et al. (1981) diagram; spectral features redward
of our data are required to distinguish the principle line excitation mechanism. We did not obtain
a redshift for WISE J100109.23+022254.5 with our data, though Brusa et al. (2010) identify this
source as a narrow-lined AGN z = 1.582 on the basis of their deep Keck/DEIMOS spectroscopy;
the quality of the redshift is not indicated. Our spectroscopy does not show any features such as
redshifted C IV emission or absorption to confirm that redshift. However, we note that strongest
feature at this redshift is likely to be [O II] emission at 9623 ˚. This is beyond the wavelength
A
coverage of our Keck spectroscopy.
Fig. 18 presents the distribution of spectroscopic redshifts for the WISE AGN candidates. We
have spectroscopic redshifts for 101 of the 130 candidates (72%); the median redshift is z = 1.11.
Seven of these candidates are from outside the IRAC AGN wedge, four of which have spectroscopic
redshifts. Two are broad-lined quasars at z ∼ 1; the other two are galaxies at z = 0.27 and z = 0.75
from zCOSMOS. This suggests that the 95% reliability rate derived in § 3.1 is actually a lower limit;
some of the WISE-selected candidates are indeed AGN despite not being identified as such by their
IRAC colors.
4. Conclusions
We use the deep, public, multiwavelength data in the ∼ 2 deg2 COSMOS survey to motivate a
very simple, empirical mid-infrared criterion to identify AGN candidates with the WISE satellite.
Selecting sources with W 1 − W 2 ≥ 0.8 identifies 61.9 ± 5.4 AGN candidates per deg2 at the 10σ
33. – 33 –
Fig. 17.— Results from Keck spectroscopy of sources identified as AGN candidates based on their
WISE colors, obtained in March 2010. All six sources here are also selected as AGN candidates
based on their Spitzer/IRAC colors (Stern et al. 2005). Prominent emission lines are marked,
as is the telluric A-band absorption at 7600 ˚. DEIMOS spectra (see Table 3) were obtained in
A
non-photometric conditions; the relative calibration of such sources should be reliable, though the
absolute scale is uncertain.
depth of the WISE COSMOS data (e.g., 160 µJy at 4.6 µm). Using deep Spitzer data in this field
and adopting the mid-infrared two-color AGN selection criteria of Stern et al. (2005) as the truth
sample, this simple WISE color cut is approximately 78% complete and 95% reliable at identifying
AGN. Of the seven ‘contaminants’ in the COSMOS field identified as AGN candidates using our
new WISE color criterion but not selected as an AGN candidate from the Spitzer color criteria,
two are identified as broad-lined quasars, implying that the reliability of this simple color selection
is better than 95% at the depth of the WISE COSMOS observations, W 2 ∼ 15.0. We caution,
however, that COSMOS, by design, is at very low ecliptic latitude implying that its WISE coverage
is shallower than average. In deeper WISE fields, this simple color cut suffers more contamination.
Here we show that the combined criteria W 1 − W 2 ≥ 0.8 and W 2 ≤ 15 robustly identifies an
34. – 34 –
Fig. 18.— Histogram of spectroscopic redshifts for WISE-selected AGN candidates in the COSMOS
field. Of the 130 such candidates, 101 have spectroscopic redshifts. The median redshift is z =
1.11.
extremely robust, highly complete AGN sample. In Assef et al. (2012), we use the deeper, wider-
area Bo¨tes field to derive a W 2-dependent AGN color selection criterion that is applicable in
o
deeper areas of the WISE all-sky survey.
Forty-six of the WISE-selected AGN candidates in the COSMOS field are known broad-lined
quasars previously identified by the SDSS (e.g., 21.9 type-1 quasars per deg2 ). The median optical-
to-mid-IR color of these type-1 AGN is i − W 2 = 4.75. The 10σ W 2 depth that we applied to
the WISE COSMOS observations corresponds to W 2 = 15.05, implying that our mid-IR WISE
AGN selection should identify unobscured quasars to an optical depth of i ∼ 19.8. Richards et al.
(2006b) combines the SDSS and 2QZ/6QZ quasar surveys to study the demographics and evolution
of quasars below the SDSS photometric limits. They find ∼ 20 type-1 quasars per deg2 to this
depth. Assuming that the other ∼ 40 WISE-selected AGN candidates per deg2 are type-2 quasars,
the implied obscured-to-unobscured ratio is ∼ 2 : 1 at these bright depths. This result is in-line
35. – 35 –
with expected ratios required to explain the intensity and hardness of the cosmic X-ray background
(e.g., Treister et al. 2004; Treister & Urry 2005; Gilli et al. 2007; Ballantyne et al. 2011).
All of the WISE-selected AGN candidates in COSMOS have optical identifications. Approxi-
mately half are spatially resolved. WISE-selected AGN tend to be amongst the optically faintest
WISE sources, accounting for essentially none of the WISE sources brighter than r = 18, ∼ 20%
of WISE sources at r = 21, and rising to > 50% of sources fainter than r = 23. The r-band dis-
tribution of WISE-selected AGN candidates peaks at r ∼ 19.5, but has a significant tail to fainter
magnitudes. Considering the 101 candidates with spectroscopic redshifts, the median redshift is
z = 1.11.
Most (∼ 75%) of the robust WISE AGN candidates covered by the deep Chandra and XMM-
Newton imaging of COSMOS are detected at X-ray energies, while few of the expected contaminants
are. Of particular note is the ∼ 25% of robust AGN candidates identified in 90 s WISE full-sky
images that are missed in extremely deep, 60+ ks pencil-beam surveys by these flagship-class soft
(< 10 keV) X-ray missions. Such sources are expected to be heavily obscured, luminous, Compton-
∼
thick AGN. In the next year, the NuSTAR satellite will map the COSMOS field in the 5 − 80 keV
hard X-ray energy range, reaching depths ∼ 200 more sensitive than previous surveys in this energy
range. We expect that several of the obscured WISE AGN candidates will be detected by NuSTAR.
The 130 WISE-selected AGN candidates identified in the COSMOS field is sufficiently large to
characterize general properties of the population, and the expectation is that this selection criterion
will be valuable for a wide range of future studies, such as understanding the energetics of sources
identified at other wavelengths (e.g., Bond et al. 2012), comparing the environments of type 1 and
type 2 AGN, and probing the role of AGN in galaxy formation and evolution. A companion paper,
Assef et al. (2012), uses nearly an order of magnitude larger sample of WISE-selected AGN in the
∼ 10 deg2 Bo¨tes field to study the evolutionary properties of this population.
o
We gratefully acknowledge the anonymous referee for helpful comments that have made the
paper both clearer and stronger. We also thank P. Capak for providing two unpublished redshifts
obtained with DEIMOS. This publication makes use of data products from the Wide-field Infrared
Survey Explorer, which is a joint project of the University of California, Los Angeles, and the
Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics
and Space Administration. We gratefully acknowledge the COSMOS survey, and are thankful for
the extensive and high quality data products that they have publicly released. This publication
makes use of data obtained at Keck Observatory. The authors wish to recognize and acknowledge
the very significant cultural role and reverence that the summit of Mauna Kea has always had
within the indigenous Hawaiian community; we are most fortunate to have the opportunity to
conduct observations from this mountain. SDSS is funded by the Alfred P. Sloan Foundation, the
Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the
National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck
Society, and the Higher Education Funding Council for England. This research has made use
36. – 36 –
of the NASA/IPAC Infrared Science Archive (IRSA), which is operated by the Jet Propulsion
Laboratory, California Institute of Technology, under contract with the National Aeronautics and
Space Administration. This work is based in part on observations made with the Spitzer Space
Telescope, which is operated by the Jet Propulsion Laboratory/California Institute of Technology,
under a contract with NASA. This work is also based in part on observations made with the
NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract
NAS 5-26555. RJA is supported by an appointment to the NASA Postdoctoral Program at the
Jet Propulsion Laboratory, administered by Oak Ridge Associated Universities through a contract
with NASA.
c 2012. All rights reserved.
A. Additional Spectroscopic Redshifts in the COSMOS Field
The three slitmasks that we observed were designed to target WISE-selected AGN candidates
in the COSMOS field, though the low source density of such sources allowed for additional spec-
troscopic targets. We primarily filled out the masks with IRAC-selected AGN candidates, using
the two-color criteria of Stern et al. (2005). Given the interest and use of the COSMOS field by a
broad community, we include those additional sources here.
Table 4 presents the results for 26 COSMOS sources for which we obtained redshifts; the six
targeted sources are listed in Table 3. We include the quality (“Q”) of each spectroscopic redshift.
Quality flag “A” signifies an unambiguous redshift determination, typically relying upon multiple
emission or absorption features. Quality flag “B” signifies a less certain redshift determination,
such as the robust detection of an isolated emission line, but where the identification of the line
is uncertain (e.g., Stern et al. 2000a). Quality flag “B” might also be assigned to a source with a
robust redshift identification, but where some uncertainty remains as to the astrometric identity of
that spectroscopic source. We consider the quality “B” results likely to be correct, but additional
spectroscopy would be beneficial. All of the spectroscopic redshifts in Table 3 are of quality “A”.
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42. – 42 –
Table 3. Results of 2010 March Keck Observations.
I814 R.A. Dec. z Slitmask(s) Notes
20.52 10:00:14.09 +02:28:38.5 1.2591 D[6] QSO: MgII,[OII],[NeIII]
20.47 10:00:36.06 +02:28:30.5 0.6883 D[5] [OII],Hβ,[OIII]
22.91 10:01:09.23 +02:22:54.5 B,D[2] faint blue cont.; z = 1.582 in Brusa et al. (2010)
19.16 10:01:14.29 +02:23:56.8 1.7997 B,D[1] QSO: Lyα,CIV,CIII],MgII
20.04 10:01:18.58 +02:27:39.1 1.0420 B QSO: CIV,CIII],MgII,[NeV],[OII],[NeIII]
18.85 10:02:32.13 +02:35:37.3 0.6568 A QSO: MgII,[NeIV],[OII]; jet?
19.30 10:00:22.79 +02:25:30.6 0.3482 D[3] Hα
Note. — Masks A and B were observed with LRIS. Mask D was observed with DEIMOS; the bracketed numbers indicate
the DEIMOS slitlet number. All derived redshifts are of very high quality (Q = A; see Appendix A).