Com o auxílio do telescópio VISTA instalado no Observatório do Paranal do ESO, astrônomos descobriram uma componente anteriormente desconhecida da Via Láctea. Ao mapear a localização de uma classe de estrelas que variam em brilho chamadas Cefeidas, foi descoberto um disco de estrelas jovens enterradas por trás de espessas nuvens de poeira no bojo central.
O rastreio público do ESO VISTA Variables in the Vía Láctea (VVV) [1] usa o telescópio VISTA instalado no Observatório do Paranal para obter imagens múltiplas em épocas diferentes das regiões centrais da nossa Galáxia nos comprimentos de onda do infravermelho [2]. O rastreio está descobrindo uma enorme quantidade de novos objetos, incluindo estrelas variáveis, aglomerados e estrelas em explosão (eso1101, eso1128, eso1141).
Uma equipe de astrônomos, liderada por Istvan Dékány da Pontificia Universidad Católica de Chile, utilizou dados deste rastreio, obtidos entre 2010 e 2014, para fazer uma descoberta notável — um componente anteriormente desconhecido da Via Láctea, a Galáxia que nos acolhe.
This document reports the first detections of Blue Straggler Stars (BSS) in the Milky Way bulge. Proper motions and variability measurements from Hubble Space Telescope observations were used to separate a clean bulge sample and identify BSS candidates. Of 42 candidate BSS identified, variability measurements indicate that at least 18 are genuine BSS, while contamination estimates suggest the true BSS population could be as high as 37 objects. This establishes for the first time that BSS exist as a population in the Milky Way bulge.
Candels the correlation_between_galaxy_morphology_and_star_formation_activity...Sérgio Sacani
This document summarizes a study investigating the relationship between galaxy morphology and star formation activity at z ~ 2 using a sample of 1,671 galaxies from CANDELS images in the GOODS-South field. The sample separates into massive, red, passive galaxies and less massive, blue, star-forming galaxies, correlating well with morphological properties. Star-forming galaxies show a variety of morphologies including clumpy structures and bulges mixed with faint disks, while passive galaxies often have compact morphologies resembling local spheroids. Similar trends are seen in local massive galaxies, suggesting the Hubble sequence was in place by z ~ 2.
This study analyzed high-resolution spectra of 125 compact stellar systems (CSSs) in the giant elliptical galaxy NGC 5128 to measure their radial velocities and velocity dispersions. Combining these measurements with structural parameters from imaging, dynamical masses were derived for 112 CSSs, including 89 for the first time. Two distinct sequences were found in the dynamical mass-to-light ratio vs dynamical mass plane, which can be approximated by power laws. The shallower sequence corresponds to bright globular clusters, while the steeper relation appears to be populated by objects requiring significant dark matter such as central black holes or concentrated dark matter. This suggests different formation histories for these CSSs compared to classical globular clusters in NGC 5128 and
This document introduces the VLT-FLAMES Tarantula Survey, which obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. The survey aims to detect massive binary systems through variations in radial velocities and to characterize the properties of O- and B-type stars, addressing questions about stellar and cluster evolution. Spectral classifications are provided for newly discovered emission-line stars, including a new Wolf-Rayet star. The survey data and reduction procedures are overviewed, and upcoming analyses of the massive star properties are announced.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
This document describes the Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES) catalog, which contains 1342 very wide (projected separation >500 AU), low-mass (at least one mid-K to mid-M dwarf component) common proper motion pairs identified from the Sloan Digital Sky Survey. The catalog was constructed using astrometry, photometry, and proper motions to identify pairs with a probability of chance alignment ≤0.05. The catalog is intended to be a resource for detailed study of low-mass binary star systems and preliminary results describe the properties and characteristics of the wide, low-mass pairs.
This document discusses the apparent evolution in average size of quenched early-type galaxies (Q-ETGs) over time. It finds that:
1) The median size of Q-ETGs increases with decreasing redshift, with half-light radii about 2-3x smaller at z=2 than locally.
2) This size evolution is primarily driven by the addition over time of larger, more diffuse Q-ETGs, not physical growth of individual galaxies.
3) Compact Q-ETGs seen at early epochs appear to be a stable population that does not evolve much in size. Their colors are consistent with passive evolution of stellar populations.
4) Newly quenched galaxies
This document summarizes a study that uses U-band photometry to determine photometric distances to young stars in the inner Galactic disk. The study focuses on the line of sight towards the Galactic longitude of 314 degrees. Photometric data is collected and calibrated using two open clusters in the field. Three groups of stars are detected at distances of 1.5, 2.5, and 5.1 kpc, which are consistent with the Carina-Sagittarius and Scutum-Crux spiral arms. The use of U-band photometry is shown to be an effective method for characterizing young star populations and making predictions about spiral structure in the Milky Way.
This document reports the first detections of Blue Straggler Stars (BSS) in the Milky Way bulge. Proper motions and variability measurements from Hubble Space Telescope observations were used to separate a clean bulge sample and identify BSS candidates. Of 42 candidate BSS identified, variability measurements indicate that at least 18 are genuine BSS, while contamination estimates suggest the true BSS population could be as high as 37 objects. This establishes for the first time that BSS exist as a population in the Milky Way bulge.
Candels the correlation_between_galaxy_morphology_and_star_formation_activity...Sérgio Sacani
This document summarizes a study investigating the relationship between galaxy morphology and star formation activity at z ~ 2 using a sample of 1,671 galaxies from CANDELS images in the GOODS-South field. The sample separates into massive, red, passive galaxies and less massive, blue, star-forming galaxies, correlating well with morphological properties. Star-forming galaxies show a variety of morphologies including clumpy structures and bulges mixed with faint disks, while passive galaxies often have compact morphologies resembling local spheroids. Similar trends are seen in local massive galaxies, suggesting the Hubble sequence was in place by z ~ 2.
This study analyzed high-resolution spectra of 125 compact stellar systems (CSSs) in the giant elliptical galaxy NGC 5128 to measure their radial velocities and velocity dispersions. Combining these measurements with structural parameters from imaging, dynamical masses were derived for 112 CSSs, including 89 for the first time. Two distinct sequences were found in the dynamical mass-to-light ratio vs dynamical mass plane, which can be approximated by power laws. The shallower sequence corresponds to bright globular clusters, while the steeper relation appears to be populated by objects requiring significant dark matter such as central black holes or concentrated dark matter. This suggests different formation histories for these CSSs compared to classical globular clusters in NGC 5128 and
This document introduces the VLT-FLAMES Tarantula Survey, which obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. The survey aims to detect massive binary systems through variations in radial velocities and to characterize the properties of O- and B-type stars, addressing questions about stellar and cluster evolution. Spectral classifications are provided for newly discovered emission-line stars, including a new Wolf-Rayet star. The survey data and reduction procedures are overviewed, and upcoming analyses of the massive star properties are announced.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
This document describes the Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES) catalog, which contains 1342 very wide (projected separation >500 AU), low-mass (at least one mid-K to mid-M dwarf component) common proper motion pairs identified from the Sloan Digital Sky Survey. The catalog was constructed using astrometry, photometry, and proper motions to identify pairs with a probability of chance alignment ≤0.05. The catalog is intended to be a resource for detailed study of low-mass binary star systems and preliminary results describe the properties and characteristics of the wide, low-mass pairs.
This document discusses the apparent evolution in average size of quenched early-type galaxies (Q-ETGs) over time. It finds that:
1) The median size of Q-ETGs increases with decreasing redshift, with half-light radii about 2-3x smaller at z=2 than locally.
2) This size evolution is primarily driven by the addition over time of larger, more diffuse Q-ETGs, not physical growth of individual galaxies.
3) Compact Q-ETGs seen at early epochs appear to be a stable population that does not evolve much in size. Their colors are consistent with passive evolution of stellar populations.
4) Newly quenched galaxies
This document summarizes a study that uses U-band photometry to determine photometric distances to young stars in the inner Galactic disk. The study focuses on the line of sight towards the Galactic longitude of 314 degrees. Photometric data is collected and calibrated using two open clusters in the field. Three groups of stars are detected at distances of 1.5, 2.5, and 5.1 kpc, which are consistent with the Carina-Sagittarius and Scutum-Crux spiral arms. The use of U-band photometry is shown to be an effective method for characterizing young star populations and making predictions about spiral structure in the Milky Way.
New m embers_of_the_tw_hydrae_association_and_two_accreting_m_dwarfs_in_scorp...Sérgio Sacani
Uma descoberta acidental de uma coleção de jovens estrelas do tipo anãs vermelhas perto do nosso Sistema Solar, poderiam nos dar uma rara ideia da formação planetária em câmera lenta. Os astrônomos da The Australian National University a ANU e a University of New South Wales, a UNSW, em Canberra, descobriram grandes discos de poeira ao redor de duas estrelas, mostrando sinais de planetas em processo de formação.
“Nós achamos que a Terra e todos os planetas se formaram de discos como esses, assim é fascinante ver um potencial novo sistema solar se formando”, disse o principal pesquisador Dr. Simon Murphy, da ANU Research School of Astronomy and Astrophysics.
“Contudo, outras estrelas dessa idade normalmente não têm mais discos. Os discos das anãs vermelhas parecem viver mais do que os de estrelas mais quentes como o Sol. Nós não entendemos por que”, disse o Dr. Murphy.
This document discusses evidence from WISE and GALEX imaging that nearby early type galaxies experienced multi-stage formation histories. Strong color gradients were found between inner and outer radii, with the outer radii being bluer by ~1 magnitude. This color difference suggests the outer regions formed ~1 Gyr after the inner regions through an inside-out formation process involving rapid early star formation within cores and later starburst events.
How to tell an accreting boson star from a black hole h. olivares et al (2020)SOCIEDAD JULIO GARAVITO
Abstract
The tentative evidences for late time “echoes” in LIGO gravitational
waves (GWs) have been claimed to be signatures of horizonless compact
objects rather than vacuum black holes (BHs) possessing horizons. In
general, in the past, many authors have considered the possibility that
the so-called BHs might be only BH mimickers (BHMs). And recently
it has been suggested that the true astrophysical BH having no intrinsic
magnetic fields may be differentiated from magnetized BHMs by studying
the radial variations of magnetic fields around pertinent compact objects
(Lobanov, Nat. Astron. 2017). Here we highlight that close to the surface
of BHMs, the magnetic field pattern differs significantly from the same for
non-relativistic Neutron Stars (B ∼ r −3 ). In particular, we point out that
for ultra- compact BHMs, the polar field is weaker than the equatorial field
1by an extremely large factor of ∼ z s /lnz s , where z s ≫ 1 is the surface
gravitational redshift. We suggest that by studying the of radial variation
as well as such significant asymmetry of magnetic field structure near the
compact object, future observations may differentiate a theoretical black
hole from a astrophysical BH mimicker (a compact object). This study
also shows that even if some BHMs would be hypothesized to possess
magnetic fields even stronger than that of magnetars, in certain cases, they
may effectively behave as atoll type neutron stars possessing extremely low
magnetic fields.
Keywords: X-ray Binaries; Active Galactic Nuclei; Magnetic Field;
Black Hole Mimickers; Relativistic Astrophysics.
PACS numbers: 04.40.Dg, 97.80.Jp, 97.60.Gb, 95.86.Nv.
This document summarizes a study that identified 195 compact elliptical galaxies across different environments using data from optical and ultraviolet sky surveys. The researchers constructed the sample by selecting galaxies that were outliers from the universal color-magnitude relation and had small sizes and high stellar velocity dispersions based on spectral modeling. They found that 7 of the galaxies were isolated, not belonging to any known galaxy groups. For these isolated galaxies, the researchers identified possible host galaxies located up to 3.3 Mpc away. The stellar populations of the isolated compact elliptical galaxies were found to be similar to those in galaxy groups and clusters, suggesting a common formation mechanism.
A spectroscopic sample_of_massive_galaxiesSérgio Sacani
This document describes a study of 16 massive galaxies at z ~ 2 selected from the 3D-HST spectroscopic survey based on the detection of a strong 4000 Angstrom break in their spectra. Spectroscopy and imaging from HST/WFC3 are used to determine accurate redshifts, stellar population properties, and structural parameters. The sample significantly increases the number of spectroscopically confirmed evolved galaxies at z ~ 2 with robust size measurements. The analysis populates the mass-size relation and finds it is consistent with local relations but with smaller sizes by a factor of 2-3. A model is presented where the observed size evolution is explained by quenching of increasingly larger star-forming galaxies at a rate set by
This document summarizes evidence that submillimeter galaxies (SMGs) at redshift 3-6 may be progenitors of compact quiescent galaxies observed at redshift 2. It compares properties of a sample of z~2 quiescent galaxies with a statistical sample of z>3 SMGs in the COSMOS field. It finds that the formation redshifts of the z~2 galaxies match the observed redshift distribution of z>3 SMGs. It also finds that the space densities and properties such as sizes, stellar masses, and internal velocities of the two populations are consistent with an evolutionary connection, assuming SMG starbursts have a duty cycle of 42+40 Myr. This suggests SMGs may represent an early burst
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
A dynamical signature_of_multiple_stellar_populations_in_47_tucanaeSérgio Sacani
The document analyzes proper motion data from Hubble Space Telescope images of the globular cluster 47 Tucanae taken over 10 years. It finds differing proper motion anisotropies between the bluest and reddest main sequence stars in 47 Tucanae, suggesting different kinematic properties for the different stellar populations. The bluest stars also exhibit the strongest central concentration. These results provide dynamical evidence for multiple stellar populations in 47 Tucanae and implications for their formation scenarios.
The Search for Distant Objects in the Solar System Using Spacewatch - Astrono...Eric Roe
This document describes a survey conducted by the Spacewatch Project to search for distant and slow-moving bright objects in the outer solar system beyond Neptune. The survey used data taken over 34 months with multiple night detections to achieve sensitivity to motions as slow as 0.012 arcsec/hr. This allowed the survey to be sensitive to Mars-sized objects out to 300 AU and Jupiter-sized planets out to 1200 AU. No large objects were found at low inclinations despite having sufficient sensitivity, allowing the authors to rule out more than one or two Pluto-sized objects to 100 AU and one or two Mars-sized objects to 200 AU for low inclinations.
This document provides a summary of Annalisa Calamida's background and experience. She is currently a postdoctoral research associate at the National Optical Astronomy Observatory studying faint white dwarfs with Hubble Space Telescope images. Her research interests include globular clusters, the Galactic bulge, stellar evolution, and variable stars. She has extensive experience reducing imaging and spectroscopic data as well as simulating observations for future telescopes. Calamida has authored or co-authored over 15 refereed publications on topics related to globular clusters and the Galactic bulge.
Disc dark matter_in_the_galaxy_and_potential_cycles_of_extraterrestrial_impac...Sérgio Sacani
This document discusses potential periodic cycles of extraterrestrial impacts, mass extinctions, and geological events on Earth. It proposes that:
1) Mass extinctions and impact cratering may exhibit cycles of around 26-30 million years that could be linked to the Sun's vertical oscillations through the Galactic plane around every 30-42 million years.
2) Near the Galactic plane, comets in the Oort Cloud could be perturbed by Galactic tidal forces and a possible thin dark matter disc, producing periodic comet showers and impacts on Earth linked to extinction events.
3) Records of geological events like tectonism and volcanism also show a potential cycle of around 30 million years that could be linked to the
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
The document summarizes a study of an extreme molecular cloud in the Antennae galaxies that has properties consistent with forming a globular cluster. ALMA observations reveal a cloud with a radius of 24 pc and mass greater than 5 million solar masses. While capable of forming a globular cluster, a lack of associated thermal radio emission indicates star formation has not yet begun to alter the environment, suggesting the cloud is in an early stage of evolution. For the cloud to be confined as observed, an external pressure over 10,000 times greater than typical interstellar pressure is required, supporting the theory that high pressures are needed to form globular clusters in extreme environments like mergers.
The ionized nebula_surrounding_the_w26_in_westerlund_1Sérgio Sacani
The document summarizes observations of an ionized nebula surrounding the red supergiant star W26 in the massive star cluster Westerlund 1. H-alpha images reveal a circumstellar shell or ring 0.1 pc in diameter surrounding the star, as well as a triangular nebula 0.2 pc away with a complex filamentary structure. Spectroscopy confirms the nebula is ionized but the excitation mechanism is unclear given red supergiants do not produce ionizing photons. The nebula and star's high luminosity and spectral variability suggest W26 is a highly evolved red supergiant experiencing extreme mass loss, making it an important case study for understanding the late stages of massive star evolution.
This thesis examines methods for detecting and estimating the masses of supermassive black holes (SMBHs) in bulgeless galaxies based on broad H-alpha emission lines. The author gathered a sample of 923 bulgeless galaxy candidates from Galaxy Zoo classifications of Sloan Digital Sky Survey images. Spectral data from SDSS was analyzed to measure properties of the H-alpha lines, which can indicate the presence of an SMBH according to the virial equation relating line width and luminosity to black hole mass. Estimated SMBH masses were compared to known relationships with host galaxy properties to test this method for identifying hidden SMBHs in bulgeless galaxies.
This document presents an analysis of metallicity gradients in the Milky Way disk as observed by the SEGUE survey. The key findings are:
1) The radial metallicity gradient (change in [Fe/H] with Galactic radius R) becomes flatter at heights above the plane (|Z|) greater than 1 kpc.
2) The median metallicity at large |Z| is consistent with outer disk open clusters, which also exhibit a flat radial gradient of [Fe/H] ∼ -0.5.
3) A flat metallicity gradient at high |Z| has implications for models of thick disk formation, as different formation scenarios predict different metallicity patterns in the thick disk.
The small blue_straggler_star_population_in_the_dense_galactic_globular_clust...Sérgio Sacani
This document summarizes a study of blue straggler star (BSS) populations in the globular cluster NGC 6752. The study used high-resolution Hubble Space Telescope images of the cluster core and wide-field ground-based images covering the outer regions. A total of 28 BSS candidates were identified in the HST images, and an additional 15 BSS candidates were found in the outer regions from the ground-based images. The radial distribution of BSS will be analyzed to understand the dynamical evolution of the cluster.
Creation of cosmic structure in the complex galaxy cluster merger abell 2744Sérgio Sacani
Abell 2744 is one of the most actively merging galaxy clusters known, appearing to have "dark", "ghost", "bullet", and "stripped" substructures of around 1014 solar masses each. The cluster shows a complex phenomenology that will challenge simulations to reproduce. The authors present a detailed strong lensing, weak lensing, and X-ray analysis of Abell 2744, identifying 34 strongly lensed images around the massive Southern core and producing the most detailed mass map to date. They find evidence that the Southern core and Northwestern substructure are post-merger systems similar to the Bullet Cluster viewed from an angle, and derive a new constraint on the self-interaction cross section of dark matter particles. They
Supplementary information spectral_evidence_for_hydrated_salts_on_mars_slopesSérgio Sacani
Novas descobertas feitas pela sonda Mars Reconnaissance Orbiter, a MRO, da NASA fornecem FORTES EVIDÊNICAS de que existe água líquida fluindo atualmente na superfície de Marte. Prestem atenção, não foi detectada água em Marte, não foi, o que foram detectadas foram indicações indiretas de que determinadas feições na superfície marciana podem ser causadas por água fluindo atualmente em sua superfície.
Ah, mas por que isso resolve um grande mistério? Pois, depois de muitas análises, do desenvolvimento de novos algoritmos de análise de imagens e de dados espectrométricos os cientistas puderam definir que as marcas escuras encontradas nos taludes de determinadas crateras podem ser causadas por água salgada fluindo na superfície. Essas marcas já foram identificadas há muitos anos, mas agora, com essas novas técnicas foi possível chegar a essa conclusão.
Usando um espectrômetro de imageamento, a bordo da sonda MRO, os pesquisadores detectaram assinaturas de minerais hidratados nos taludes onde misteriosas listras são vistas no Planeta Vermelho. Essas listras escurecidas aparecem como fluxos e refluxos no passar do tempo. Elas se escurecem e parecem fluir pelos íngremes taludes durante as estações mais quentes, e então se apagam nas estações mais frias. Elas aparecem em alguns locais em Marte quando as temperaturas estão acima de -23 graus Celsius, e desaparecem em épocas mais frias.
O telescópio de rastreio VISTA do ESO encontrou uma horda de galáxias massivas anteriormente ocultas por poeira, que existiram quando o Universo era ainda bebê. Ao descobrir e estudar uma grande quantidade deste tipo de galáxias, os astrônomos descobriram, exatamente e pela primeira vez, quando é que tais monstros apareceram pela primeira vez no Universo.
O simples fato de contar o número de galáxias que existem em determinada área do céu permite aos astrônomos testar teorias de formação e evolução galática. No entanto, uma tarefa aparentemente tão fácil torna-se mais difícil quando tentamos contar galáxias cada vez mais distantes e tênues e é mais complicada ainda devido ao fato das galáxias mais brilhantes e fáceis de observar — as mais massivas no Universo — se tornarem mais raras à medida que os astrônomos observam o passado do Universo, enquanto que as galáxias menos brilhantes, mas muito mais numerosas, são ainda mais difíceis de detectar.
Uma equipe de astrônomos liderada por Karina Caputi do Instituto Astronômico Kapteyn da Universidade de Groningen, descobriu muitas galáxias distantes que não tinham sido detectadas anteriormente. A equipe utilizou imagens do rastreioUltraVISTA, um dos seis projetos que usam o VISTA para mapear o céu no infravermelho próximo, e fez um censo das galáxias tênues quando a idade do Universo estava compreendida entre 0,75 e 2,1 bilhões de anos.
New m embers_of_the_tw_hydrae_association_and_two_accreting_m_dwarfs_in_scorp...Sérgio Sacani
Uma descoberta acidental de uma coleção de jovens estrelas do tipo anãs vermelhas perto do nosso Sistema Solar, poderiam nos dar uma rara ideia da formação planetária em câmera lenta. Os astrônomos da The Australian National University a ANU e a University of New South Wales, a UNSW, em Canberra, descobriram grandes discos de poeira ao redor de duas estrelas, mostrando sinais de planetas em processo de formação.
“Nós achamos que a Terra e todos os planetas se formaram de discos como esses, assim é fascinante ver um potencial novo sistema solar se formando”, disse o principal pesquisador Dr. Simon Murphy, da ANU Research School of Astronomy and Astrophysics.
“Contudo, outras estrelas dessa idade normalmente não têm mais discos. Os discos das anãs vermelhas parecem viver mais do que os de estrelas mais quentes como o Sol. Nós não entendemos por que”, disse o Dr. Murphy.
This document discusses evidence from WISE and GALEX imaging that nearby early type galaxies experienced multi-stage formation histories. Strong color gradients were found between inner and outer radii, with the outer radii being bluer by ~1 magnitude. This color difference suggests the outer regions formed ~1 Gyr after the inner regions through an inside-out formation process involving rapid early star formation within cores and later starburst events.
How to tell an accreting boson star from a black hole h. olivares et al (2020)SOCIEDAD JULIO GARAVITO
Abstract
The tentative evidences for late time “echoes” in LIGO gravitational
waves (GWs) have been claimed to be signatures of horizonless compact
objects rather than vacuum black holes (BHs) possessing horizons. In
general, in the past, many authors have considered the possibility that
the so-called BHs might be only BH mimickers (BHMs). And recently
it has been suggested that the true astrophysical BH having no intrinsic
magnetic fields may be differentiated from magnetized BHMs by studying
the radial variations of magnetic fields around pertinent compact objects
(Lobanov, Nat. Astron. 2017). Here we highlight that close to the surface
of BHMs, the magnetic field pattern differs significantly from the same for
non-relativistic Neutron Stars (B ∼ r −3 ). In particular, we point out that
for ultra- compact BHMs, the polar field is weaker than the equatorial field
1by an extremely large factor of ∼ z s /lnz s , where z s ≫ 1 is the surface
gravitational redshift. We suggest that by studying the of radial variation
as well as such significant asymmetry of magnetic field structure near the
compact object, future observations may differentiate a theoretical black
hole from a astrophysical BH mimicker (a compact object). This study
also shows that even if some BHMs would be hypothesized to possess
magnetic fields even stronger than that of magnetars, in certain cases, they
may effectively behave as atoll type neutron stars possessing extremely low
magnetic fields.
Keywords: X-ray Binaries; Active Galactic Nuclei; Magnetic Field;
Black Hole Mimickers; Relativistic Astrophysics.
PACS numbers: 04.40.Dg, 97.80.Jp, 97.60.Gb, 95.86.Nv.
This document summarizes a study that identified 195 compact elliptical galaxies across different environments using data from optical and ultraviolet sky surveys. The researchers constructed the sample by selecting galaxies that were outliers from the universal color-magnitude relation and had small sizes and high stellar velocity dispersions based on spectral modeling. They found that 7 of the galaxies were isolated, not belonging to any known galaxy groups. For these isolated galaxies, the researchers identified possible host galaxies located up to 3.3 Mpc away. The stellar populations of the isolated compact elliptical galaxies were found to be similar to those in galaxy groups and clusters, suggesting a common formation mechanism.
A spectroscopic sample_of_massive_galaxiesSérgio Sacani
This document describes a study of 16 massive galaxies at z ~ 2 selected from the 3D-HST spectroscopic survey based on the detection of a strong 4000 Angstrom break in their spectra. Spectroscopy and imaging from HST/WFC3 are used to determine accurate redshifts, stellar population properties, and structural parameters. The sample significantly increases the number of spectroscopically confirmed evolved galaxies at z ~ 2 with robust size measurements. The analysis populates the mass-size relation and finds it is consistent with local relations but with smaller sizes by a factor of 2-3. A model is presented where the observed size evolution is explained by quenching of increasingly larger star-forming galaxies at a rate set by
This document summarizes evidence that submillimeter galaxies (SMGs) at redshift 3-6 may be progenitors of compact quiescent galaxies observed at redshift 2. It compares properties of a sample of z~2 quiescent galaxies with a statistical sample of z>3 SMGs in the COSMOS field. It finds that the formation redshifts of the z~2 galaxies match the observed redshift distribution of z>3 SMGs. It also finds that the space densities and properties such as sizes, stellar masses, and internal velocities of the two populations are consistent with an evolutionary connection, assuming SMG starbursts have a duty cycle of 42+40 Myr. This suggests SMGs may represent an early burst
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
A dynamical signature_of_multiple_stellar_populations_in_47_tucanaeSérgio Sacani
The document analyzes proper motion data from Hubble Space Telescope images of the globular cluster 47 Tucanae taken over 10 years. It finds differing proper motion anisotropies between the bluest and reddest main sequence stars in 47 Tucanae, suggesting different kinematic properties for the different stellar populations. The bluest stars also exhibit the strongest central concentration. These results provide dynamical evidence for multiple stellar populations in 47 Tucanae and implications for their formation scenarios.
The Search for Distant Objects in the Solar System Using Spacewatch - Astrono...Eric Roe
This document describes a survey conducted by the Spacewatch Project to search for distant and slow-moving bright objects in the outer solar system beyond Neptune. The survey used data taken over 34 months with multiple night detections to achieve sensitivity to motions as slow as 0.012 arcsec/hr. This allowed the survey to be sensitive to Mars-sized objects out to 300 AU and Jupiter-sized planets out to 1200 AU. No large objects were found at low inclinations despite having sufficient sensitivity, allowing the authors to rule out more than one or two Pluto-sized objects to 100 AU and one or two Mars-sized objects to 200 AU for low inclinations.
This document provides a summary of Annalisa Calamida's background and experience. She is currently a postdoctoral research associate at the National Optical Astronomy Observatory studying faint white dwarfs with Hubble Space Telescope images. Her research interests include globular clusters, the Galactic bulge, stellar evolution, and variable stars. She has extensive experience reducing imaging and spectroscopic data as well as simulating observations for future telescopes. Calamida has authored or co-authored over 15 refereed publications on topics related to globular clusters and the Galactic bulge.
Disc dark matter_in_the_galaxy_and_potential_cycles_of_extraterrestrial_impac...Sérgio Sacani
This document discusses potential periodic cycles of extraterrestrial impacts, mass extinctions, and geological events on Earth. It proposes that:
1) Mass extinctions and impact cratering may exhibit cycles of around 26-30 million years that could be linked to the Sun's vertical oscillations through the Galactic plane around every 30-42 million years.
2) Near the Galactic plane, comets in the Oort Cloud could be perturbed by Galactic tidal forces and a possible thin dark matter disc, producing periodic comet showers and impacts on Earth linked to extinction events.
3) Records of geological events like tectonism and volcanism also show a potential cycle of around 30 million years that could be linked to the
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
The document summarizes a study of an extreme molecular cloud in the Antennae galaxies that has properties consistent with forming a globular cluster. ALMA observations reveal a cloud with a radius of 24 pc and mass greater than 5 million solar masses. While capable of forming a globular cluster, a lack of associated thermal radio emission indicates star formation has not yet begun to alter the environment, suggesting the cloud is in an early stage of evolution. For the cloud to be confined as observed, an external pressure over 10,000 times greater than typical interstellar pressure is required, supporting the theory that high pressures are needed to form globular clusters in extreme environments like mergers.
The ionized nebula_surrounding_the_w26_in_westerlund_1Sérgio Sacani
The document summarizes observations of an ionized nebula surrounding the red supergiant star W26 in the massive star cluster Westerlund 1. H-alpha images reveal a circumstellar shell or ring 0.1 pc in diameter surrounding the star, as well as a triangular nebula 0.2 pc away with a complex filamentary structure. Spectroscopy confirms the nebula is ionized but the excitation mechanism is unclear given red supergiants do not produce ionizing photons. The nebula and star's high luminosity and spectral variability suggest W26 is a highly evolved red supergiant experiencing extreme mass loss, making it an important case study for understanding the late stages of massive star evolution.
This thesis examines methods for detecting and estimating the masses of supermassive black holes (SMBHs) in bulgeless galaxies based on broad H-alpha emission lines. The author gathered a sample of 923 bulgeless galaxy candidates from Galaxy Zoo classifications of Sloan Digital Sky Survey images. Spectral data from SDSS was analyzed to measure properties of the H-alpha lines, which can indicate the presence of an SMBH according to the virial equation relating line width and luminosity to black hole mass. Estimated SMBH masses were compared to known relationships with host galaxy properties to test this method for identifying hidden SMBHs in bulgeless galaxies.
This document presents an analysis of metallicity gradients in the Milky Way disk as observed by the SEGUE survey. The key findings are:
1) The radial metallicity gradient (change in [Fe/H] with Galactic radius R) becomes flatter at heights above the plane (|Z|) greater than 1 kpc.
2) The median metallicity at large |Z| is consistent with outer disk open clusters, which also exhibit a flat radial gradient of [Fe/H] ∼ -0.5.
3) A flat metallicity gradient at high |Z| has implications for models of thick disk formation, as different formation scenarios predict different metallicity patterns in the thick disk.
The small blue_straggler_star_population_in_the_dense_galactic_globular_clust...Sérgio Sacani
This document summarizes a study of blue straggler star (BSS) populations in the globular cluster NGC 6752. The study used high-resolution Hubble Space Telescope images of the cluster core and wide-field ground-based images covering the outer regions. A total of 28 BSS candidates were identified in the HST images, and an additional 15 BSS candidates were found in the outer regions from the ground-based images. The radial distribution of BSS will be analyzed to understand the dynamical evolution of the cluster.
Creation of cosmic structure in the complex galaxy cluster merger abell 2744Sérgio Sacani
Abell 2744 is one of the most actively merging galaxy clusters known, appearing to have "dark", "ghost", "bullet", and "stripped" substructures of around 1014 solar masses each. The cluster shows a complex phenomenology that will challenge simulations to reproduce. The authors present a detailed strong lensing, weak lensing, and X-ray analysis of Abell 2744, identifying 34 strongly lensed images around the massive Southern core and producing the most detailed mass map to date. They find evidence that the Southern core and Northwestern substructure are post-merger systems similar to the Bullet Cluster viewed from an angle, and derive a new constraint on the self-interaction cross section of dark matter particles. They
Supplementary information spectral_evidence_for_hydrated_salts_on_mars_slopesSérgio Sacani
Novas descobertas feitas pela sonda Mars Reconnaissance Orbiter, a MRO, da NASA fornecem FORTES EVIDÊNICAS de que existe água líquida fluindo atualmente na superfície de Marte. Prestem atenção, não foi detectada água em Marte, não foi, o que foram detectadas foram indicações indiretas de que determinadas feições na superfície marciana podem ser causadas por água fluindo atualmente em sua superfície.
Ah, mas por que isso resolve um grande mistério? Pois, depois de muitas análises, do desenvolvimento de novos algoritmos de análise de imagens e de dados espectrométricos os cientistas puderam definir que as marcas escuras encontradas nos taludes de determinadas crateras podem ser causadas por água salgada fluindo na superfície. Essas marcas já foram identificadas há muitos anos, mas agora, com essas novas técnicas foi possível chegar a essa conclusão.
Usando um espectrômetro de imageamento, a bordo da sonda MRO, os pesquisadores detectaram assinaturas de minerais hidratados nos taludes onde misteriosas listras são vistas no Planeta Vermelho. Essas listras escurecidas aparecem como fluxos e refluxos no passar do tempo. Elas se escurecem e parecem fluir pelos íngremes taludes durante as estações mais quentes, e então se apagam nas estações mais frias. Elas aparecem em alguns locais em Marte quando as temperaturas estão acima de -23 graus Celsius, e desaparecem em épocas mais frias.
O telescópio de rastreio VISTA do ESO encontrou uma horda de galáxias massivas anteriormente ocultas por poeira, que existiram quando o Universo era ainda bebê. Ao descobrir e estudar uma grande quantidade deste tipo de galáxias, os astrônomos descobriram, exatamente e pela primeira vez, quando é que tais monstros apareceram pela primeira vez no Universo.
O simples fato de contar o número de galáxias que existem em determinada área do céu permite aos astrônomos testar teorias de formação e evolução galática. No entanto, uma tarefa aparentemente tão fácil torna-se mais difícil quando tentamos contar galáxias cada vez mais distantes e tênues e é mais complicada ainda devido ao fato das galáxias mais brilhantes e fáceis de observar — as mais massivas no Universo — se tornarem mais raras à medida que os astrônomos observam o passado do Universo, enquanto que as galáxias menos brilhantes, mas muito mais numerosas, são ainda mais difíceis de detectar.
Uma equipe de astrônomos liderada por Karina Caputi do Instituto Astronômico Kapteyn da Universidade de Groningen, descobriu muitas galáxias distantes que não tinham sido detectadas anteriormente. A equipe utilizou imagens do rastreioUltraVISTA, um dos seis projetos que usam o VISTA para mapear o céu no infravermelho próximo, e fez um censo das galáxias tênues quando a idade do Universo estava compreendida entre 0,75 e 2,1 bilhões de anos.
The search for_extraterrestrial_civilizations_with_large_energy_suppliesSérgio Sacani
This document discusses potential signatures that could distinguish transiting megastructures from exoplanets. It identifies nine potential anomalous signatures:
1) Non-disk shapes could produce anomalous transit light curves.
2) Non-gravitational forces could cause orbits inconsistent with the star's density.
3) "Swarms" of many structures could cause irregular or aperiodic transit signals.
4) Structures large enough to completely occult the star could be detected.
5) Very low inferred masses would be anomalous for objects blocking significant starlight.
6) Nearly achromatic eclipses would differ from exoplanets' atmosphere-influenced transits.
3d modeling of_gj1214b_atmosphere_formation_of_inhomogeneous_high_cloouds_and...Sérgio Sacani
Uma equipe de cientistas da Universidade de Washington e da Universidade de Toronto foram os primeiros a simular nuvens exóticas em 3D na atmosfera de um exoplaneta.
O objeto em questão, é o GJ 1214b, um exoplaneta chamado de mini-Netuno que foi descoberto, seis anos atrás pelos astrônomos no Harvard-Smithsonian Center for Astrophysics.
Também conhecido como Gliese 1214b, esse mundo tem cerca de 2.7 vezes o diâmetro da Terra e uma massa quase 7 vezes maior que a massa do nosso planeta. Ele está localizado a cerca de 52 anos-luz de distância na constelação de Ophiuchus.
O planeta orbita a estrela anã vermelha, GJ 1214, a cada 38 horas, a uma distância de 1.3 milhões de milhas.
De acordo com estudos prévios, o planeta tem uma atmosfera rica em água ou hidrogênio com extensas nuvens.
“Deve existir altas nuvens ou uma névoa orgânica na atmosfera – como nós observamos em Titã. Sua temperatura atmosférica excede o ponto de fusão da água”, disse o Dr. Benjamin Charnay, um dos membros da equipe da Universidade de Washington.
The neowise discovered_comet_population_and_the_co_co2_production_ratesSérgio Sacani
Após o seu lançamento em 2009, a sonda NEOWISE da NASA já observou 163 cometas durante a missão primária WISE/NEOWISE. Essa amostra do telescópio espacial representa a maior pesquisa infravermelha de cometas já feitas até o momento. Os dados dessa pesquisa estão dando uma nova ideia sobre a poeira, o tamanho dos núcleos do cometa, e a taxa de produção dos gases difíceis de serem observados como dióxido de carbono e monóxido de carbono. Os resultados do censo do NEOWISE dos cometas foram recentemente publicados no Astrophysical Journal.
O monóxido de carbono (CO) e o dióxido de carbono (CO2) são moléculas comuns encontradas no ambiente do início do Sistema Solar, e nos cometas. Na maior parte das circunstâncias, a sublimação do gelo de água provavelmente guia a atividade nos cometas quando eles chegam perto do Sol, mas em distâncias maiores e em temperaturas mais frias, outras moléculas como o CO e o CO2 podem ser os principais guias. O dióxido e o monóxido de carbono são moléculas difíceis de serem detectadas da terra, devido a abundância dessas moléculas na própria atmosfera terrestre que podem obscurecer o sinal. A sonda NEOWISE vaga além da atmosfera da Terra, fazendo essas medidas dos gases emitidos pelos cometas possíveis.
“Essa é a primeira vez que nós observamos essa grande evidência estatística do monóxido de carbono obtida enquanto o gás do cometa é emitido quando ele está mais distante do Sol”, disse James Bauer, vice-principal pesquisador da missão NEOWISE do Laboratório de Propulsão a Jato da NASA em Pasadena, na Califórnia, e autor do artigo. “Emitindo o que é provavelmente monóxido de carbono além de 4 Unidades Astronômicas, ou seja, 600 milhões de quilômetros, isso nos mostra que os cometas podem ter guardado a maior parte dos gases quando eles se formaram, e ficaram ali guardados por bilhões de anos. A maioria dos cometas que nós observamos ativos além das 4 Unidades Astronômicas, são cometas de períodos longos, cometas com períodos orbitais maiores que 200 anos que gastam a maior parte da sua vida além da órbita de Netuno”.
This document summarizes observations of the star KIC 8462852 from the Kepler space telescope. Key points:
- Kepler observed irregular dips in the star's brightness up to 22% over its 4-year mission. These dips lasted from 5-80 days and occurred at irregular intervals.
- Follow-up observations characterized KIC 8462852 as a main sequence F3V/IV star with a rotation period of 0.88 days and no significant infrared excess.
- Various scenarios are considered to explain the dips, including dust clumps or exocomet fragments passing in front of the star. The scenario best fitting current data involves a family of exocomet fragments
Radio continum emission_of_35_edge_on_galaxies_observed_with_the_vlaSérgio Sacani
Usando um dos maiores rádio observatórios do mundo, o Very Large Array do National Radio Astronomy, um grupo de astrônomos descobriram que os halos ao redor dos discos das galáxias espirais são muito mais comuns do que se pensava anteriormente.
A equipe, dirigida pela Dra. Judith Irwin, da Universidade de Queens, em Kingston, ON, Canadá, observou 35 galáxias espirais próximas de lado, de 11 a 137 milhões de anos-luz de distância da Terra.
As galáxias espirais, como a nossa própria Via Láctea ou a famosa Galáxia de Andrômeda, possuem uma vasta maioria de suas estrelas, gás, e poeira num disco plano em rotação com braços espirais. A maior parte da luz e das ondas de rádio observadas com telescópios veem de objetos localizados nesse disco.
“Nós sabíamos antes que alguns halos existiam, mas, usando o poder total do VLA atualizado e o poder total de algumas técnicas de processamento de imagens, nós descobrimos que esses halos são muito mais comuns entre as galáxias espirais do que nós pensávamos antes”, explicou a Dra. Irwin.
On the theory_and_future_cosmic_planet_formationSérgio Sacani
A Terra chegou cedo para a festa no universo em evolução. De acordo com um novo estudo teórico, quando o nosso Sistema Solar nasceu a 4.6 bilhões de anos atrás, somente 8% dos planetas possivelmente habitáveis que serão formados no universo, existiam. E, a festa não terminaria até quando o Sol queimasse por outros 6 bilhões de anos. A totalidade desses planetas, 92%, não tinham nascido.
Essa conclusão é baseada no acesso dos dados coletados pelo Telescópio Espacial Hubble da NASA e o prolífico caçador de exoplanetas, o Observatório Espacial Kepler.
“Nossa principal motivação foi entender o lugar da Terra no contexto do resto do universo”, disse o autor do estudo Peter Behroozi do Space Telescope Science Institute (STScI), em Baltimore, Maryland, “Comparado a todos os planetas que irão se formar no universo, a Terra, na verdade chegou cedo”.
Olhando distante no espaço e no tempo, o Hubble, tem dado aos astrônomos um verdadeiro “álbum de família”, das observações da galáxia que mostra a história da formação do universo à medida que as galáxias cresciam. Os dados mostram que o universo estava gerando estrelas numa taxa elevada a 10 bilhões de anos atrás, mas a fração do gás hidrogênio e hélio do universo que estava envolvida era muito baixa. Hoje, o nascimento de estrelas está acontecendo numa taxa muito mais lenta do que a muito tempo atrás, mas existe muito gás deixado para trás disponível que o universo continuará gerando estrelas e planetas por muito tempo ainda.
First discovery of_a_magnetic_field_in_a_main_sequence_delta_scuti_star_the_k...Sérgio Sacani
Coralie Neiner do Laboratory for Space Studies and Astrophysics Instrumentation, LESIA (CNRS/Observatoire de Paris/UPMC/Université Paris Diderot) e Patricia Lampens (Royual OIbservatory of Belgium), descobriram a primeira estrela magnética do tipo delta Scuti, através de observações espectropolarimétricas, realizadas com o telescópio CFHT. As estrelas do tipo delta Scuti, são estrelas pulsantes, sendo que algumas delas mostram assinaturas atribuídas para um segundo tipo de pulsação. A descoberta mostra que isso é na verdade a assinatura de um campo magnético. Essa descoberta tem importantes implicações para o entendimento do interior das estrelas.
Dois tipos de estrelas pulsantes existem entre as estrelas com massa entre 1.5 e 2.5 vezes a massa do Sol: as estrelas do tipo delta Scuti e as estrelas do tipo gamma Dor. A teoria nos diz que as estrelas com temperatura entre 6900 e 7400 graus Kelvin podem ter ambos os tipos de pulsação. Essas são então chamadas de estrelas híbridas. Contudo, o satélite Kepler da NASA tem detectado um grande número de estrelas híbridas com temperaturas maiores ou menores do que esse limite pensado anteriormente. A existência dessas estrelas híbridas com temperaturas maiores é algo muito controverso, já que desafia o nosso entendimento sobre as estrelas pulsantes do tipo delta Scuti e gamma Dor.
Astrônomos, usando os dados do Telescópio Espacial de Raios-Gamma Fermi da NASA detectaram pistas de mudanças periódicas no brilho de uma chamada galáxia “ativa”, cujas emissões são alimentadas por um buraco negro gigante. Se confirmada, a descoberta marcaria a primeira emissão cíclica de raios-gamma com anos de duração, já detectada de qualquer galáxia, o que forneceria novas ideias sobre os processos físicos que ocorrem nas proximidades de um buraco negro.
“Observando muitos anos de dados obtidos pelo Large Area Telescope, o LAT, do Fermi, nós identificamos indicações de uma variação com aproximadamente dois anos de comprimento de raios-gamma emitidos pela galáxia conhecida como PG 1553+113”, disse Stefano Ciprini, que coordenou a equipe do Fermi no Centro de Dados Científicos, o ASDC, da Agência Espacial Italiana, em Roma. “Esse sinal é sutil, e dura menos do que 4 ciclos, assim, do mesmo modo que é algo espetacular de se ver é algo que precisa de mais observações”.
Buracos negros supermassivos com uma massa de milhões de vezes a massa do Sol, localizam-se no coração da maioria das galáxias, incluindo a nossa Via Láctea. Em cerca de 1% dessas galáxias, o buraco negro monstruoso, irradia energia equivalente à bilhões de vezes a energia do Sol, emissões que podem variar em escala de tempo de minutos a anos. Os astrônomos se referem a essas como sendo galáxias ativas.
Mais da metade das fontes de raios-gamma observadas pelo LAT do Fermi, são galáxias ativas, chamadas de blazars, como a PG 1553+113. À medida que a matéria cai em direção ao seu buraco negro supermassivo, algumas partículas subatômicas escapam numa velocidade próxima à velocidade da luz em um par de jatos apontados em direções opostas. O que faz um blazar tão brilhante é que um desses jatos de partículas podem estar diretamente apontados para nós.
Flaring from the_supermassive_black_hole_in_mrk335_studied_with_swift_and_nustarSérgio Sacani
Os comportamentos estranhos e desconcertantes dos buracos negros tornam-se cada dia menos misteriosos, com as novas observações feitas com as missões Swift e NuSTAR da NASA. Os dois telescópios espaciais registraram um buraco negro supermassivo no meio de uma gigantesca explosão de luz de raio-X, ajudando os astrônomos a tentarem resolver um grande quebra-cabeça: Como os buracos negros supermassivos emitem flares?
Os resultados sugerem que os buracos negros supermassivos emitem flares de raios-X, quando suas coroas circundantes, fontes de partículas extremamente energéticas, são atiradas ou lançadas para fora dos buracos negros.
“Essa é a primeira vez que nós somos capazes de linkar o lançamento da coroa com uma flare”, disse Dan Wilkins, da Universidade de Saint Mary em Halifax, no Canadá e principal autor do artigo que descreve os resultados na revista Monthly Notices of The Royal Astronomical Society. “Isso nos ajudará a entender como os buracos negros supermassivos alimentam alguns dos objetos mais brilhantes do universo”.
Os buracos negros supermassivos não emitem luz por si só, mas eles as vezes são circundados por discos de material quente e brilhante. A gravidade do buraco negro puxa o gás ao redor, aquecendo esse material e fazendo com que ele brilhe com diferentes tipos de luz. Outra fonte da radiação perto do buraco negro é a coroa. As coroas são feitas de partículas altamente energéticas que geram luz de raio-X, mas os detalhes sobre sua aparência, ou como elas se formam, ainda não são claros.
A rocky planet_transiting_a_nearby_low_mass_starSérgio Sacani
Um exoplaneta rochoso do tamanho da Terra, orbita uma estrela pequena e próxima, poderia ser o mundo mais importante já encontrado além do Sistema Solar, disseram os astrônomos.
O planeta localiza-se na constelação de Vela, no hemisfério sul do céu e é próximo o suficiente para que os telescópios possam observar qualquer atmosfera que ele possua, um procedimento que poderia ajudar a registrar algum tipo de vida, se ela existisse em outros planetas, no futuro.
Denominado de GJ 1132b, o exoplaneta é cerca de 16% maior que a Terra, e está localizado a cerca de 39 anos-luz de distância, o que faz com que ele seja três vezes mais próximo da Terra do que qualquer outro exoplaneta rochoso já descoberto. Nessa distância, espera-se que os telescópios sejam capazes de fazer uma análise química de sua atmosfera, a velocidade dos seus ventos e as cores do pôr-do-Sol, que acontecem no exoplaneta.
Os astrônomos registraram o planeta à medida que ele passava na frente da sua estrela, uma estrela do tipo anã vermelha, com somente um quinto do tamanho do Sol. Apesar de muito mais fria e muito mais apagada que o Sol, o GJ 1132b, tem uma órbita tão próxima da estrela que as suas temperaturas superficiais atingem cerca de 260 graus Celsius.
Essa temperatura, obviamente, é muito alta para reter a água em estado líquido na superfície do exoplaneta, fazendo com que ele seja inóspito para a vida, mas não tão quente para queimar toda uma atmosfera que pode ter se formado no planeta.
Variability in a_young_lt_transition_planetary_mass_objectSérgio Sacani
Padrões climáticos num misterioso mundo além do nosso Sistema Solar tem sido revelado pela primeira vez, sugere um estudo.
Camadas de nuvens, feitas de poeira quente e gotículas de ferro derretido, foram detectadas num objeto parecido com um planeta descoberto a 75 anos-luz de distância da Terra, dizem os pesquisadores.
As descobertas poderiam melhorar a habilidade dos cientistas de descobrir se condições em planetas distantes seriam capazes de sustentar a vida.
Uma equipe de pesquisadores liderada pela Universidade de Edimburgo, usou um telescópio no Chile para estudar o sistema climático de um mundo distante, conhecido como PSO J318.5-22, que estima-se tenha cerca de 20 milhões de anos de vida.
Os pesquisadores capturaram centenas de imagens infravermelhas do objeto enquanto ele rotacionava em torno do seu próprio eixo num período de 5 horas. Comparando o brilho do PSO J318.5-22, com corpos vizinhos, a equipe descobriu que ele era coberto por múltiplas camadas de nuvens finas e espessas. Essas nuvens causaram as mudanças no brilho do mundo distante enquanto ele executava o seu movimento de rotação, dizem os cientistas.
A higher efficiency_of_converting_gas_to_stars_push_galaxies_at_z_1_6_well_ab...Sérgio Sacani
Galáxias formando estrelas em taxas extremas a nove bilhões de anos atrás eram mais eficientes do que a média das galáxias atuais, descobriram os pesquisadores.
A maioria das estrelas acredita-se localizam-se na sequência principal onde quanto maior a massa da galáxia, mais eficiente ela é na formação de novas estrelas. Contudo, de vez em quando uma galáxia apresentará uma explosão de novas estrelas que brilham mais do que o resto. Uma colisão entre duas grandes galáxias é normalmente a causa dessas fases de explosões de formação de estrelas, onde o gás frio que reside nas grandes nuvens moleculares torna-se o combustível para sustentar essas altas taxas de formação de estrelas.
A questão que os astrônomos têm feito é se essas explosões de estrelas no início o universo foram o resultado de se ter um suprimento de gás abundante, ou se as galáxias convertiam o gás de maneira mais eficiente.
Um novo estudo, publicado no Astrophysical Journal Letters de 15 de Outubro, liderado por John Silverman, do Kavli Institute for Physics and Mathematics of the Universe, estudou o conteúdo do gás monóxido de carbono (CO) em sete galáxias de explosão de estrelas muito distantes, quando o universo tinha apenas 4 bilhões de anos de vida. Isso foi possível devido a capacidade do Atacama Large Millimiter/Submillimiter Array (ALMA), localizado no platô no topo da montanha no Chile, que trabalha para detectar as ondas eletromagnéticas no comprimento de onda milimétrico (importante para se estudar o gás molecular) e um nível de sensibilidade que só agora começa a ser explorado pelos astrônomos.
Os pesquisadores descobriram que a quantidade de gás CO emitido já tinha diminuído, mesmo apesar da galáxia continuar a formar estrelas em altas taxas. Essas observações são similares àquelas registradas para as galáxias de explosões de estrelas próximas da Terra atualmente, mas a quantidade da depleção de gás não foi tão rápida quanto se esperava. Isso levou os pesquisadores a concluírem que poderia haver um contínuo aumento na eficiência, dependendo em de quanto acima da taxa de se formar estrelas ela está da sequência principal.
The document discusses key facts and figures about the International Space Station (ISS). It provides statistics on the number of spacewalks, launches, pressurized volume, weight in orbit, meals eaten, lines of code, power generated, and people involved. It lists 59 countries that have participated in ISS utilization and research accomplishments from Expeditions 0-24, including the number of investigations conducted, completed, led by international partners, and from national labs. Scientific publications from research on the ISS are also mentioned.
Astronaut Reid Wiseman tweeted a photo from the International Space Station showing a toy from his childhood floating in space. The document then provides a summary of the most impressive space photos from 2014, including photos taken by Wiseman from the ISS of Earth's landscapes, cities, natural disasters and the moon. It concludes with several close up photos of astronomical objects and phenomena taken by NASA satellites and space telescopes.
First results from_the_hubble_opal_program_jupiter_in_2015Sérgio Sacani
Os cientistas usando o Telescópio Espacial Hubble da NASA/ESA produziram novos mapas de Júpiter, que mostram as contínuas mudanças que ocorrem com a famosa Grande Mancha Vermelha. As imagens também revelam uma rara estrutura em forma de onda na atmosfera do planeta que não tinha sido vista por décadas. A nova imagem é a primeira de uma série de retratos anuais dos planetas externos do Sistema Solar, que nos darão um novo olhar desses mundos remotos, e ajudarão os cientistas a estudarem como eles mudam com o passar do tempo.
Nessa nova imagem de Júpiter, uma grande quantidade de feições foi capturada incluindo ventos, nuvens e tempestades. Os cientistas por trás dessas novas imagens, as obtiveram usando a Wide Field Camera 3 do Hubble, num período de observação de mais de 10 horas e produziram assim dois mapas completos do planeta, a partir das suas observações. Esses mapas fizeram com que fosse possível determinar a velocidade dos ventos em Júpiter, com a finalidade de identificar diferentes fenômenos na sua atmosfera além de traquear as suas feições mais famosas.
As novas imagens confirmam que a grande tempestade que tem existido na superfície de nuvens de Júpiter por no mínimo 300 anos, continua a encolher, mas mesmo que desapareça, ela irá morrer lutando. A tempestade, conhecida como Grande Mancha Vermelha, é vista aqui fazendo seus movimentos em espiral no centro da imagem do planeta. Ela tem diminuído de tamanho de maneira muito rápida de ano em ano. Mas agora, a taxa de encolhimento parece ter reduzido novamente, mesmo apesar da mancha ser cerca de 240 quilômetros menor do que era em 2014.
Reference Guide To The International Space StationSérgio Sacani
The International Space Station is a unique place – a convergence of science, technology and human innovation that demonstrates new technologies and makes research breakthroughs not possible on Earth.
It is a microgravity laboratory in which an international crew of six people live and work while traveling at a speed of five miles per second, orbiting Earth every 90 minutes.
The space station has been continuously occupied since November 2000. In that time, more than 200 people from 15 countries have visited.
Crew members spend about 35 hours each week conducting research in many disciplines to advance scientific knowledge in Earth, space, physical, and biological sciences for the benefit of people living on our home planet.
The station facilitates the growth of a robust commercial market in low-Earth orbit, operating as a national laboratory for scientific research and facilitating the development of U.S. commercial cargo and commercial crew space transportation capabilities.
More than an acre of solar arrays provide power to the station, and also make it the next brightest object in the night sky after the moon. You don’t even need a telescope to see it zoom over your house. And we’ll even send you a text message or email alert to let you know when (and where) to look up, spot the station, and wave!
Dark side of_comet_67_p_churyumov_gerasiemnko_in_august_october_2014Sérgio Sacani
Usando o instrumento Microwave Instrument for Rosetta Orbiter (MIRO), os cientistas estão estudando a região polar sul do cometa no final de sua longa estação de inverno. Os dados sugerem que essas regiões frias e escuras abrigam gelo nas suas primeiras dezenas de centímetros abaixo da superfície em quantidades muito maiores do que as encontradas em outras áreas do cometa.
Desde a sua chegada no Cometa 67P/Churyumov-Gerasimenko, a Rosetta tem pesquisado a superfície e o ambiente desse corpo de forma curiosa. Mas por um longo período de tempo, uma porção do núcleo, as regiões frias e escuras ao redor do polo sul do cometa, permaneceram inacessíveis para quase todos os instrumentos a bordo da sonda.
Devido a uma combinação de sua forma em lobo duplo e a inclinação do seu eixo de rotação, o cometa da Rosetta, tem um padrão sazonal muito peculiar durante a sua órbita de 6.5 anos. As estações estão distribuídas de maneira muito assimétrica entre os dois hemisférios, cada um deles compreende parte tanto dos lobos como do pescoço do cometa.
Na maior parte da órbita do cometa, o hemisfério norte experimenta um verão muito longo, durando cerca de 5.5 anos, e o hemisfério sul passa por um longo, frio e escuro inverno. Contudo, poucos meses antes do cometa passar pelo seu periélio, o ponto na sua órbita, mais próximo do Sol, a situação muda, e o hemisfério sul passa por um breve porém quente verão.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
Hubble Space Telescope Observations of NGC 253 Dwarf Satellites: Three Ultra-...Sérgio Sacani
We present deep Hubble Space Telescope (HST) imaging of five faint dwarf galaxies associated with the nearby
spiral NGC 253 (D ≈ 3.5 Mpc). Three of these are newly discovered dwarf galaxies, while all five were found in
the Panoramic Imaging Survey of Centaurus and Sculptor, a Magellan+Megacam survey to identify faint dwarfs
and other substructures in resolved stellar light around massive galaxies outside of the Local Group. Our HST data
reach 3 magnitudes below the tip of the red giant branch for each dwarf, allowing us to derive their distances,
structural parameters, and luminosities. All five systems contain mostly old, metal-poor stellar populations
(age ∼12 Gyr, [M/H] −1.5) and have sizes (rh ∼ 110–3000 pc) and luminosities (MV ∼ −7 to −12 mag) largely
consistent with Local Group dwarfs. The three new NGC 253 satellites are among the faintest systems discovered
beyond the Local Group. We also use archival H I data to place limits on the gas content of our discoveries. Deep
imaging surveys such as our program around NGC 253 promise to elucidate the faint end of the satellite luminosity
function and its scatter across a range of galaxy masses, morphologies, and environments in the decade to come
The fornax deep_survey_with_vst_i_the_extended_and_diffuse_stellar_halo_of_ng...Sérgio Sacani
We have started a new deep, multi-imaging survey of the Fornax cluster, dubbed Fornax Deep
Survey (FDS), at the VLT Survey Telescope. In this paper we present the deep photometry inside
two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that
the core of the Fornax cluster is characterised by a very extended and diffuse envelope surrounding
the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (∼ 192 kpc)
from the galaxy center and down to μg ∼ 31 mag arcsec−2 in the g band. The deep photometry
allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399
and towards NGC 1387. By analyzing the integrated colors of this feature, we argue that it
could be due to the ongoing interaction between the two galaxies, where the outer envelope of
NGC 1387 on its east side is stripped away. By fitting the light profile, we found that exists a
physical break radius in the total light distribution at R = 10 arcmin (∼ 58 kpc) that sets the
transition region between the bright central galaxy and the outer exponential halo, and that the
stellar halo contributes for 60% of the total light of the galaxy (Sec. 3.5). We discuss the main
implications of this work on the build-up of the stellar halo at the center of the Fornax cluster.
By comparing with the numerical simulations of the stellar halo formation for the most massive
BCGs (i.e. 13 < logM200/M⊙ < 14), we find that the observed stellar halo mass fraction is
consistent with a halo formed through the multiple accretion of progenitors with stellar mass in
the range 108 − 1011 M⊙. This might suggest that the halo of NGC 1399 has also gone through
a major merging event. The absence of a significant number of luminous stellar streams and
tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early
formation epoch. Therefore, differently from the Virgo cluster, the extended stellar halo around
NGC 1399 is characterised by a more diffuse and well-mixed component, including the ICL.
Exploring the nature and synchronicity of early cluster formation in the Larg...Sérgio Sacani
We analyse Hubble Space Telescope observations of six globular clusters in the Large Magel- lanic Cloud (LMC) from programme GO-14164 in Cycle 23. These are the deepest available observations of the LMC globular cluster population; their uniformity facilitates a precise comparison with globular clusters in the Milky Way. Measuring the magnitude of the main- sequence turn-off point relative to template Galactic globular clusters allows the relative ages of the clusters to be determined with a mean precision of 8.4 per cent, and down to 6 per cent for individual objects. We find that the mean age of our LMC cluster ensemble is identical to the mean age of the oldest metal-poor clusters in the Milky Way halo to 0.2 ± 0.4 Gyr. This provides the most sensitive test to date of the synchronicity of the earliest epoch of globular cluster formation in two independent galaxies. Horizontal branch magnitudes and subdwarf fitting to the main sequence allow us to determine distance estimates for each cluster and examine their geometric distribution in the LMC. Using two different methods, we find an average distance to the LMC of 18.52 ± 0.05.
Star formation at the smallest scales; A JWST study of the clump populations ...Sérgio Sacani
We present the clump populations detected in 18 lensed galaxies at redshifts 1 to 8.5 within the lensing cluster field SMACS0723.
The recent JWST Early Release Observations of this poorly known region of the sky have revealed numerous point-like sources
within and surrounding their host galaxies, undetected in the shallower HST images. We use JWST multiband photometry and
the lensing model of this galaxy cluster to estimate the intrinsic sizes and magnitudes of the stellar clumps. We derive optical
restframe effective radii from <10 to hundreds pc and masses ranging from ∼ 105
to 109 M, overlapping with massive star
clusters in the local universe. Clump ages range from 1 Myr to 1 Gyr. We compare the crossing time to the age of the clumps
and determine that between 45 and 60 % of the detected clumps are consistent with being gravitationally bound. On average,
the dearth of Gyr old clumps suggests that the dissolution time scales are shorter than 1 Gyr. We see a significant increase in the
luminosity (mass) surface density of the clumps with redshift. Clumps in reionisation era galaxies have stellar densities higher
than star clusters in the local universe. We zoom in into single galaxies at redshift < 6 and find for two galaxies, the Sparkler and
the Firework, that their star clusters/clumps show distinctive colour distributions and location surrounding their host galaxy that
are compatible with being accredited or formed during merger events. The ages of some of the compact clusters are between
1 and 4 Gyr, e.g., globular cluster precursors formed around 9-12 Gyr ago. Our study, conducted on a small sample of galaxies,
shows the potential of JWST observations for understanding the conditions under which star clusters form in rapidly evolving
galaxies.
A giant thin stellar stream in the Coma Galaxy ClusterSérgio Sacani
The study of dynamically cold stellar streams reveals information about the gravitational potential where they reside and provides
important constraints on the properties of dark matter. However, the intrinsic faintness of these streams makes their detection beyond
Local environments highly challenging. Here, we report the detection of an extremely faint stellar stream (µg,max = 29.5 mag arcsec−2
)
with an extraordinarily coherent and thin morphology in the Coma Galaxy Cluster. This Giant Coma Stream spans ∼510 kpc in length
and appears as a free-floating structure located at a projected distance of 0.8 Mpc from the center of Coma. We do not identify any
potential galaxy remnant or core, and the stream structure appears featureless in our data. We interpret the Giant Coma Stream as
being a recently accreted, tidally disrupting passive dwarf. Using the Illustris-TNG50 simulation, we identify a case with similar
characteristics, showing that, although rare, these types of streams are predicted to exist in Λ-CDM. Our work unveils the presence
of free-floating, extremely faint and thin stellar streams in galaxy clusters, widening the environmental context in which these objects
are found ahead of their promising future application in the study of the properties of dark matter.
This pilot survey used modest aperture telescopes to image 8 nearby spiral galaxies in order to search for stellar tidal streams. Ultra-deep imaging revealed 6 previously undetected extensive (up to 30 kpc) stellar structures likely from tidally disrupted satellites. A diversity of tidal feature morphologies was found, including great circle-like streams, remote shells, and jets emerging from disks. Simulations predict tidal debris should be common and match the observed variety, providing evidence minor mergers have shaped disk galaxies since z=1.
This document discusses a study that used difference imaging techniques to search for variable stars and microlensing events in the elliptical galaxy Centaurus A. The study obtained deep photometric data over almost two months using the Wide Field Imager on the ESO/MPG 2.2 m telescope. It detected 271 variable stars in Centaurus A with a detection limit of magnitude 24.5. Based on a simple model of Centaurus A's halo, the study estimated it could detect around 4 microlensing events per year, but a higher sensitivity is needed for a meaningful microlensing survey. The spatial distribution of any microlensing events could help constrain the shape of Centaurus A's dark matter halo.
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
The massive relic galaxy NGC 1277 is dark matter deficient From dynamical mod...Sérgio Sacani
According to the Λ cold dark matter (ΛCDM) cosmology, present-day galaxies with stellar masses M? > 1011 M should contain
a sizable fraction of dark matter within their stellar body. Models indicate that in massive early-type galaxies (ETGs) with M? ≈
1.5 × 1011 M, dark matter should account for ∼15% of the dynamical mass within one effective radius (1 Re) and for ∼60% within
5 Re
. Most massive ETGs have been shaped through a two-phase process: the rapid growth of a compact core was followed by the
accretion of an extended envelope through mergers. The exceedingly rare galaxies that have avoided the second phase, the so-called
relic galaxies, are thought to be the frozen remains of the massive ETG population at z & 2. The best relic galaxy candidate discovered
to date is NGC 1277, in the Perseus cluster. We used deep integral field George and Cynthia Mitchel Spectrograph (GCMS) data to
revisit NGC 1277 out to an unprecedented radius of 6 kpc (corresponding to 5 Re). By using Jeans anisotropic modelling, we find
a negligible dark matter fraction within 5 Re (fDM(5 Re) < 0.05; two-sigma confidence level), which is in tension with the ΛCDM
expectation. Since the lack of an extended envelope would reduce dynamical friction and prevent the accretion of an envelope, we
propose that NGC 1277 lost its dark matter very early or that it was dark matter deficient ab initio. We discuss our discovery in the
framework of recent proposals, suggesting that some relic galaxies may result from dark matter stripping as they fell in and interacted
within galaxy clusters. Alternatively, NGC 1277 might have been born in a high-velocity collision of gas-rich proto-galactic fragments,
where dark matter left behind a disc of dissipative baryons. We speculate that the relative velocities of ≈2000 km s−1
required for the
latter process to happen were possible in the progenitors of the present-day rich galaxy clusters.
1) The VVV survey discovered a new globular cluster candidate, named VVV CL001, near the known globular cluster UKS 1 in the direction of the Galactic bulge.
2) Photometry of UKS 1 from the VVV survey was used to measure its reddening as E(B-V)=2.2 mag, distance modulus as (m-M)0=16.01 mag, and distance as 15.9 kpc.
3) Near-infrared color-magnitude diagrams of VVV CL001 suggest it has similar reddening as UKS 1 and is at least as metal-poor, though its distance remains uncertain. Further observations are needed to confirm if they are
This summarizes a scientific study on long-distance quantum teleportation between two laboratories separated by 55 meters but connected by 2 kilometers of fiber optic cable. The key points are:
1) Researchers teleported quantum states (qubits) carried by photons at 1.3 micrometer wavelengths onto photons at 1.55 micrometer wavelengths between the two laboratories.
2) The qubits were encoded in time-bin superpositions and entanglement rather than polarization to make them more robust against decoherence in optical fibers.
3) A partial Bell state measurement was performed using linear optics at the receiving end to probabilistically teleport the quantum states over the long distance.
A three-dimensional map of the Milky Way using 66,000 Mira variable starsSérgio Sacani
We study the three-dimensional structure of the Milky Way using 65,981 Mira variable stars discovered
by the Optical Gravitational Lensing Experiment (OGLE) survey. The spatial distribution of the Mira
stars is analyzed with a model containing three barred components that include the X-shaped boxy
component in the Galactic center (GC), and an axisymmetric disk. We take into account the distance
uncertainties by implementing the Bayesian hierarchical inference method. The distance to the GC is
R0 = 7.66 ± 0.01(stat.) ± 0.39(sys.) kpc, while the inclination of the major axis of the bulge to the
Sun-GC line-of-sight is θ = 20.2
◦ ± 0.6
◦
(stat.) ± 0.7
◦
(sys.). We present, for the first time, a detailed
three-dimensional map of the Milky Way composed of young and intermediate-age stellar populations.
Our analysis provides independent evidence for both the X-shaped bulge component and the flaring
disk (being plausibly warped). We provide the complete dataset of properties of Miras that were used
for calculations in this work. The table includes: mean brightness and amplitudes in nine photometric
bands (covering a range of wavelength from 0.5 to 12 µm), photometric chemical type, estimated
extinction, and calculated distance with its uncertainty for each Mira variable. The median distance
accuracy to a Mira star is at the level of 6.6%.
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
A giant ring_like_structure_at_078_z_086_displayed_by_gr_bsSérgio Sacani
This document describes the discovery of a giant ring-like structure in the observable universe displayed by 9 gamma ray bursts (GRBs) between redshifts of 0.78 and 0.86. The ring has a diameter of 1720 Mpc, over five times larger than the expected transition scale to homogeneity. The ring lies at a distance of 2770 Mpc with major and minor diameters of 43° and 30°, respectively. The probability of this structure occurring by random chance is calculated to be 2 × 10-6. This ring-shaped feature contradicts the cosmological principle of large-scale homogeneity and isotropy, and the physical mechanism responsible is unknown.
Two super-Earths at the edge of the habitable zone of the nearby M dwarf TOI-...Sérgio Sacani
The main scientific goal of TESS is to find planets smaller than Neptune around stars bright enough to allow further characterization studies. Given
our current instrumentation and detection biases, M dwarfs are prime targets to search for small planets that are in (or nearby) the habitable zone
of their host star. Here we use photometric observations and CARMENES radial velocity measurements to validate a pair of transiting planet
candidates found by TESS. The data was fitted simultaneously using a Bayesian MCMC procedure taking into account the stellar variability
present in the photometric and spectroscopic time series. We confirm the planetary origin of the two transiting candidates orbiting around TOI-
2095 (TIC 235678745). The star is a nearby M dwarf (d = 41:90 0:03 pc, Te = 3759 87 K, V = 12:6 mag) with a stellar mass and radius
of M? = 0:44 0:02 M and R? = 0:44 0:02 R, respectively. The planetary system is composed of two transiting planets: TOI-2095b with an
orbital period of Pb = 17:66484 (7 105) days and TOI-2095c with Pc = 28:17232 (14 105) days. Both planets have similar sizes with
Rb = 1:250:07 R and Rc = 1:330:08 R for planet b and c, respectively.We put upper limits on the masses of these objects with Mb < 4:1 M
for the inner and Mc < 7:4 M for the outer planet (95% confidence level). These two planets present equilibrium temperatures in the range of 300
- 350 K and are close to the inner edge of the habitable zone of their star.
Sdss1133 an unsually_perssitent_transient_in_a_nearby_dwarf_galaxySérgio Sacani
This document summarizes observations of SDSS1133, an unusual transient object offset from the center of a nearby dwarf galaxy. SDSS1133 has been detected in observations spanning 63 years, and exhibits broad emission lines and strong variability. While initially classified as a supernova due to its non-detection in 2005, more recent observations over the past decade show it has rebrightened over a magnitude and displays properties consistent with both an active galactic nucleus and luminous blue variable star eruptions. Its nature remains ambiguous between an extreme example of pre-supernova mass loss or a potential candidate for a recoiling supermassive black hole.
Similar to The vvv survey_reveals_classical_cepheids_tracing_a_young_and_thin_stellar_disk_across_the_galaxys_bulge (20)
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 (
�
(
�
−
�
)
∼
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-
�
Ca-rich population. Although such an object is too red for any low-
�
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
�
) with
Λ
CDM. Therefore unlike low-
�
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-
�
truly diverge from their low-
�
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.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfSelcen Ozturkcan
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
Travis Hills of MN is Making Clean Water Accessible to All Through High Flux ...Travis Hills MN
By harnessing the power of High Flux Vacuum Membrane Distillation, Travis Hills from MN envisions a future where clean and safe drinking water is accessible to all, regardless of geographical location or economic status.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
Targeting Hsp90 and its pathogen Orthologs with Tethered Inhibitors as a Diagnostic and Therapeutic Strategy for cancer and infectious diseases with Dr. Timothy Haystead.
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...
The vvv survey_reveals_classical_cepheids_tracing_a_young_and_thin_stellar_disk_across_the_galaxys_bulge
1. The VVV Survey reveals classical Cepheids tracing a young and
thin stellar disk across the Galaxy’s bulge
I. D´ek´any1,2
, D. Minniti3,1,4
, D. Majaess5,6
, M. Zoccali2,1
, G. Hajdu2,1
, J. Alonso-Garc´ıa7,1
,
M. Catelan2,1
, W. Gieren8,1
, J. Borissova9,1
1
Instituto Milenio de Astrof´ısica, Santiago, Chile.
2
Instituto de Astrof´ısica, Facultad de F´ısica, Pontificia Universidad Cat´olica de Chile, Av.
Vicu˜na Mackenna 4860, Santiago, Chile.
3
Departamento de F´ısica, Facultad de Ciencias Exactas, Universidad Andres Bello,
Rep´ublica 220, Santiago, Chile.
4
Vatican Observatory, V00120 Vatican City State, Italy.
5
Saint Mary’s University, Halifax, Nova Scotia, Canada.
6
Mount Saint Vincent University, Halifax, Nova Scotia, Canada.
7
Unidad de Astronom´ıa, Universidad de Antofagasta, Av. U. de Antofagasta 02800,
Antofagasta, Chile.
8
Departamento de Astronom´ıa, Universidad de Concepci´on, Casilla 160-C, Concepci´on,
Chile
9
Instituto de F´ısica y Astronom´ıa, Universidad de Valpara´ıso, Av. Gran Breta˜na 1111,
Valparaso, Chile.
ABSTRACT
Solid insight into the physics of the inner Milky Way is key to understand-
ing our Galaxy’s evolution, but extreme dust obscuration has historically hin-
dered efforts to map the area along the Galactic mid-plane. New comprehensive
near-infrared time-series photometry from the VVV Survey has revealed 35 clas-
sical Cepheids, tracing a previously unobserved component of the inner Galaxy,
namely a ubiquitous inner thin disk of young stars along the Galactic mid-plane,
traversing across the bulge. The discovered period (age) spread of these classical
Cepheids implies a continuous supply of newly formed stars in the central region
of the Galaxy over the last 100 million years.
Subject headings: Galaxy:general, Galaxy:bulge, Galaxy:disk, Galaxy:stellar con-
tent, stars: variables: Cepheids
2. – 2 –
1. Introduction
The inner Milky Way is dominated by a peanut-shaped bulge (McWilliam & Zoccali
2010; Wegg & Gerhard 2013) that flares up from a prominent Galactic bar (Nakada et al.
1991), and its structural and kinematical properties are consistent with a formation scenario
driven by the instabilities of a multi-component stellar disk (Ness et al. 2013; Zoccali et al.
2014; Gardner et al. 2014; Ness et al. 2014; Di Matteo et al. 2015). The majority of its
constituent stars are very ( 8 billion years) old (Ortolani et al. 1995; Zoccali et al. 2003;
Brown et al. 2010), implying that its formation occurred at early epochs of the Milky Way’s
evolution. Although intermediate-age stars are also present in the bulge (van Loon et al. 2003;
Bensby et al. 2013), their origin, nature and ubiquity are poorly understood, owing partly
to sizable age uncertainties and possible biases from small sample sizes and contamination
by foreground disk stars. Yet it is well known that the innermost core (R 300 pc) of the
Galaxy hosts stars with ages ranging from a few million to several billion years (e.g., Serabyn
& Morris 1996; van Loon et al. 2003; Matsunaga et al. 2011). This “nuclear bulge” has rather
distinct physical properties from the rest of the bulge and is related to the Central Molecular
Zone, but neither its transition to the surrounding bulge regions nor the triggering process
for star formation and its history are well understood (see, e.g., Launhardt et al. 2002).
Our global picture of the inner Galaxy is linked primarily to observations of the outer
bulge, i.e., at Galactic latitudes higher than ∼ 2◦
. That deficit arises from extreme obscura-
tion by interstellar dust, high source density, and confusion with foreground disk populations.
The properties of the bulge region at low latitudes have thus remained largely unexplored,
leaving ambiguities concerning the interplay of the nuclear bulge and the various components
of the boxy bulge and surrounding outer stellar disk. The VISTA Variables in the V´ıa L´actea
(VVV) ESO Public Survey (Minniti et al. 2010) presents a means to ameliorate the situation
by opening the time-domain in the near-infrared. That is particularly important as classes
of variable stars, such as classical Cepheids, are indicators of young stellar populations (e.g.,
Catelan & Smith 2015), and can yield critical insight as demonstrated here.
2. Discovery and Characterisation of the Cepheids
We performed a comprehensive near-infrared variability search using VVV Survey data
collected between 2010 and 2014, in a ∼ 66 square degree area in the central bulge (−10.5◦
l +10◦
, −1.7◦
b +2◦
, aligned with VVV image borders). We excluded two fields
lying toward the nuclear bulge owing to extreme source crowding. Time-series photometry
for ∼ 108
point sources were analyzed, with up to 70 Ks-band measurements per object,
together with color information from 1–5 independent measurements in the Z, Y , J, and
3. – 3 –
H bands. The data processing, calibration, and light-curve analysis were conducted in the
same way as in our previous study on the Twin Cepheids beyond the bulge (D´ek´any et al.
2015), and are based on standard VVV Survey data products (Minniti et al. 2010; Irwin et
al. 2004; Catelan et al. 2013). We detected a sample of approximately 3 · 105
objects which
displayed putative light variations, and scanned the results for Cepheids possessing pulsation
periods in the range of 4–50 days. The lower limit mitigates confusion between the pulsation
modes (e.g., Macri et al. 2015), while the upper limit was constrained by the sampling of
the photometric time-series. We found 655 fundamental-mode Cepheid candidates based
on their periods, amplitudes, and asymmetric light-curve shapes. A large fraction of these
objects were only detected in the H and Ks bands given the extreme reddening.
For computing the distances and extinctions of the Cepheids, we employed the period-
luminosity (PL) relations (a.k.a. Leavitt Law, Monson et al. 2012; Matsunaga et al. 2009)
adopted in our previous study (D´ek´any et al. 2015), adjusted to match the latest and most
accurate distance modulus for the Large Magellanic Cloud (LMC, Pietrzy´nski et al. 2013).
The color excess was converted to an extinction using a selective-to-absolute extinction
ratio found towards the Galactic Center (GC, Nishiyama et al. 2009), once converted into
the VISTA photometric system (see D´ek´any et al. 2015). For each object, a distance and
extinction were computed under both the assumptions that the target is a classical and a
type II Cepheid. We subsequently identified the correct solution and class upon further
analysis.
Following the approach adopted in our previous study (D´ek´any et al. 2015), uncertainties
tied to the distance and extinction were estimated by Monte Carlo simulations. The distances
exhibit 1-3% precision and 8-10% accuracy. The latter is dominated by the uncertainty in
the adopted extinction curve. The systematic uncertainty might be larger, possibly up
to ∼ 20%, if variations in the extinction’s wavelength dependence, either as a function of
Galactic longitude or along the sight-line, significantly exceed those found previously toward
the inner bulge (Nishiyama et al. 2009).
Type II Cepheids, i.e. old, low-mass, He-shell burning pulsating stars in the classical
instability strip (Catelan & Smith 2015), populate the same range of periods as classical
Cepheids. The two Cepheid classes share similar near-infrared light-curves (see, e.g. Catelan
& Smith 2015; Matsunaga et al. 2011; D´ek´any et al. 2015). Since the bulge contains a
sizable population of type II Cepheids with a centrally concentrated distribution (Soszy´nski
et al. 2011), our sample is expected to be dominated by these objects. Therefore, additional
observational information is required to identify classical Cepheids in our sample. The critical
information is conveyed by an extinction map of the bulge, based on the analysis of its red
clump stars (Gonzalez et al. 2012).
4. – 4 –
Classical and type II Cepheids have similar intrinsic colors but rather different lumi-
nosities (Monson et al. 2012; Matsunaga et al. 2009), and consequently their PL relations
yield similar extinctions but very different distances when applied to the same object. A
Cepheid’s type can be determined if its distance and extinction are inconsistent with the
cumulative extinction up to the bulge in its direction, computed under one of the two possi-
ble assumptions for its type (Matsunaga et al. 2011; D´ek´any et al. 2015). Figure. 1a-b show
the difference between the extinction values predicted by the PL relations and the bulge
extinction map, normalized by its uncertainty as a function of distance, when extinction and
distance are computed under the assumption that all detected Cepheids are either classical
or type II. There are several Cepheids in our sample for which the computed extinction was
within 3σ agreement with, or higher than the predicted cumulative extinction up to the
bulge towards their sight-lines, but for which the type II assumption yields short distances
(3 − 4 kpc), making them bona fide classical Cepheid candidates. While most of them reside
in the disk at the far side of the bulge as expected, we found 35 stars (green points in Fig. 1)
that are likewise located within the bulge volume (see, e.g., Wegg & Gerhard 2013).
These 35 stars could be type II Cepheids only if they were located by chance beyond thick
dust clouds of small angular sizes (< 1 ), otherwise the 2 ×2 resolution of the VVV reddening
map would be sensitive to those. To investigate this unlikely possibility, we examined the
color images and analyzed the color-magnitude diagrams (CMD’s) of the stellar fields around
these Cepheids, in search of anomalously high gradients in the foreground extinction. In all
cases, the CMDs are inconsistent with the presence of such nearby foreground clouds, down
to angular sizes of ∼ 10 , where the surface density of the disk population becomes too
low for drawing such conclusion. That limiting angular scale would correspond to physical
sizes of 0.2 pc, smaller than a typical Bok globule (Das et al. 2015). The probability
for such chance alignment is negligible, and that it affects all 35 objects is virtually zero.
Consequently, we rule out the possibility that they are nearby type II Cepheids in the
Galactic disk, and classify them as classical Cepheids located inside the bulge volume. Their
light-curves are presented in Fig. 2, while Fig. 3 conveys their spatial distribution. Their
properties are summarized in Table 1.
By reversing the arguments above, 425 new type II Cepheids are identified in the central
bulge (Fig. 1a-b, red points), with extinctions consistent with predictions from the VVV
reddening map (Gonzalez et al. 2012). If these stars were classical Cepheids, they would be
located far beyond the bulge, and their corresponding extinctions would be inconsistent with
such large distances. The detailed study of these objects and the rest of the new classical
Cepheids beyond the bulge will be presented in forthcoming papers.
To bolster the classification of the classical and type II Cepheids in our sample, the
5. – 5 –
distributions of their amplitudes and positions were compared. The middle panel of Fig. 1
displays the period-amplitude diagram of these objects with previously known classical and
type II Cepheids. Although these parameters do not allow us to unambiguously separate the
two types, particularly at shorter periods, the locus of the newly discovered classical Cepheid
population agrees with that of other classical Cepheids in the Local Group. Furthermore,
the right panel of Fig. 1 compares the spatial distributions of classical and type II Cepheids
identified in this study. While the type II objects are expectedly concentrated towards the
GC (Soszy´nski et al. 2011), the classical Cepheids are rather evenly distributed. The lack of
classical Cepheids toward small longitudes, and the slightly offset peak from zero longitude
in the density of type II Cepheids, arise from the central gap in the coverage (cf. Fig. 3).
The sample of 35 new classical Cepheids is incomplete owing to the bright magnitude
limit of the VVV Survey. Brighter longer-period Cepheids (Monson et al. 2012) can be satu-
rated in the VVV images in the absence of significant foreground extinction. The asymmetry
in the classical Cepheids’ observed number density distribution, with more objects at the
far side of the bulge (Fig. 3), is an observational bias owing to that saturation limit. The
typical Ks limit where saturation cannot be calibrated out is ∼ 11 mag. The faint detection
limit towards the central bulge is Ks ∼ 15.5 mag. These estimates are time-varying, and
depend on the seeing, sky transparency, and crowding.
Figure 4 conveys the detection threshold in period–extinction parameter space for clas-
sical Cepheids, at various distances. Short-period objects near the 4d
lower limit are detected
throughout the entire range of observed extinction. However, nearly half of our sample would
be overlooked in the absence of significant reddening if they were located at the near side of
the bulge. Consequently, the asymmetry in the objects’ observed spatial distribution, with
more Cepheids further away (Fig. 3), is an observational bias owing to the saturation limit
of the VVV Survey.
On the other hand, the observed small vertical spread of the classical Cepheids cannot be
attributed to a similar observational bias. While long-period classical Cepheids further from
the Galactic plane and occupying the bulge would remain undetected by the VVV Survey,
more than half our sample would still be detected if they were located at considerably higher
Galactic latitudes. That is apparent when comparing the distributions of Fig. 4 and the mean
bulge extinction as a function of Galactic latitude in the VVV extinction map (Gonzalez et
al. 2012, see also Fig. 3, lower panel). Bulge Cepheids exhibiting periods less than 15 days
would be detected up to latitudes of 1◦
at most longitudes, while those with periods below
8 days would be found at latitudes typically up to 2◦
.
6. – 6 –
3. The inner thin disk
The 35 new classical Cepheids inside the bulge volume span across the entire longitudinal
range of our study and lie in close proximity to the Galactic mid-plane. The standard
deviation of their vertical distances from it is only 22 pc, with the farthest Cepheid being
only 82 pc above it. This vertical distribution is less than estimates of relatively nearby
classical Cepheids (Majaess et al. 2009), whereby the latter exhibit a scale height of ∼ 75 pc.
All classical Cepheids discovered are younger than 100 Myr, since a Cepheid’s pulsation
period is closely linked to its age (Bono et al. 2005). The youngest Cepheid observed may be
∼ 25 million years old (Bono et al. 2005). We cannot exclude the possible presence of even
younger and brighter Cepheids, which would be saturated in the VVV Survey. Our objects
thus trace an underlying young and thin inner stellar disk along the Galactic plane. Although
their census may be incomplete, it is noteworthy that both short- and long-period Cepheids
were detected, while in the nuclear bulge only Cepheids with periods close to 20 days are
known. The period spread implies that they originate from continuous star formation along
the mid-plane in the central Galaxy over the last ∼ 100 million years.
A limiting factor that hinders a detailed analysis of the spatial distribution of Cepheids
in the inner Galaxy is the uncertainty in the wavelength dependence of interstellar extinction,
i.e., the properties of interstellar dust particles along the sight-line. However, the bulk of
the classical Cepheids in our sample remain within 3 kpc of the GC if we consider different
extinction curves (e.g., Cardelli et al. 1989; Fitzpatrick 1999), even if they have not been
observed to be valid towards the inner bulge. For instance, adopting the “standard” Galactic
extinction curve (Cardelli et al. 1989) would shift the mean Cepheid distance ∼ 1.5 kpc
closer, and only 2 objects would become further than 3 kpc from the GC (in the near disk).
The discovery of a thin star-forming inner disk across the bulge is immune to the effects of
potentially anomalous extinction.
Cepheid extinction estimates derived from PL relations were compared to the VVV
extinction map (Gonzalez et al. 2012). The comparison is nearly split between values that
generally agree, and Cepheids that exhibit significant (> 3σ) positive deviations from this
map’s predictions. These anomalies may originate from localized absorbing material rather
than scale height differences between the two populations. Since bulge red clump stars are
detected to small angular radii (∼ 10 ) around all the Cepheids, most of the material should
be distributed inside the bulge’s volume and along the sight-lines of objects with extreme
extinction. Several of these Cepheids are in the angular vicinity ( 30 ) of ionized hydrogen
bubbles, embedded young stellar objects, or extended mid-infrared objects visible in images
of the GLIMPSE (Churchwell et al. 2009) surveys (see Table 1).
7. – 7 –
4. Conclusion
The presence of numerous classical Cepheids demonstrate that the central Galaxy con-
tains a very young (< 100 Myr old) stellar population spanning well outside the nuclear
bulge. Our results transcend earlier evidence for intermediate-age stars in the bulge volume
(e.g., van Loon et al. 2003; Bensby et al. 2013) by exploring low-latitude regions where stud-
ies of stellar ages were unobtainable. A hitherto unobserved component of the inner Galaxy
was identified, namely a young inner thin disk along the Galactic mid-plane. The confined
vertical extent, together with the wide longitudinal breadth of the Cepheids’ spatial distri-
bution, suggest that this stellar disk has a smooth transition from both the nuclear bulge
and the Galactic thin disk that encompasses the bulge region.
The findings discussed here are in general agreement with recent numerical results con-
cerning the ages of stellar constituents residing in the inner Galaxy. In simulated disk galaxies
forming stars from cooling gas inside a dark matter halo, a sizable population of young and
metal-rich stars emerged in close proximity to the plane, within a radius of ∼ 2 kpc from the
centers. Having a median age of ∼ 1 Gyr and a large age dispersion, these simulated stars
show evidence that the presence of young stars in an old bulge can follow naturally from
a model galaxy’s evolution (Ness et al. 2014). Yet continued investigations are needed to
assess whether the Cepheids in the inner disk were born in situ, possibly from star formation
stemming from gas inflow towards the GC (e.g., Kormendy & Kennicutt 2004), or if they
originate from further out, either being formed at the bar ends (Phillips 1996) or captured
from the outer disk by a growing bar (Martinez-Valpuesta et al. 2006). Constraining the
Cepheids’ orbits by kinematical measurements would supply critical information for resolving
this point. Another important question is whether the young stars in the inner disk evolve
dynamically as old bulge stars once did, and thus will eventually flare into the boxy outer
bulge. Such a secular process could supply younger metal-rich stars to the predominantly
old outer bulge (Bensby et al. 2013). Given that disk galaxies with small bulges such as ours
are common, understanding their stellar components’ fundamental properties, interactions,
and coevolution is key in our quest to understand galaxy evolution as a whole.
We gratefully acknowledge the use of data from the ESO Public Survey program 179.B-
2002, taken with the VISTA telescope, and data products from the Cambridge Astronomical
Survey Unit. The authors acknowledge the following funding sources: BASAL CATA PFB-
06, the Chilean Ministry of Economy’s ICM grant IC120009, FIC-R Fund (project 30321072),
CONICYT-PCHA (Doctorado Nacional 2014-63140099), CONICYT Anillo ACT 1101, and
FONDECYT projects 1141141, 1130196, 3130552, 1120601, and 1150345.
Facilities: ESO:VISTA.
8. – 8 –
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This preprint was prepared with the AAS LATEX macros v5.2.
10. – 10 –
-5
0
5
10
15
20
2 4 6 8 10 12 14
dA(Ks)/[dA(Ks)]
distance if all type II [kpc]
a new bulge type II Cep.
bulge / inner disk classical Cep.
-5
0
5
10
15
20
5 10 15 20 25 30 35 40
dA(Ks)/[dA(Ks)]
distance if all classical [kpc]
b new bulge type II Cep.
bulge / inner disk classical Cep.
0
0.2
0.4
0.6
0.8
1
1.2
0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Ks-bandtotalamplitude[mag]
log ( Period / day )
cnew bulge type II Cep.
bulge+GC. type II Cep.
LMC+Gal. cl. Cep.
bulge / inner disk
classical Cep.
NumberofCepheids
Galactic longitude [deg.]
dnew bulge
type II Cep.
bulge / inner disk
classical Cep.
0
10
20
30
40
50
60
70
-12-10-8-6-4-2024681012
Fig. 1.— The selection of classical Cepheids. Panel a: Under the assumption that all
Cepheids in our sample are of type II, this figure shows the deviation of their computed
extinction relative to the VVV reddening map (Gonzalez et al. 2012) divided by the uncer-
tainty, as a function of the distance. Error bars show 1σ uncertainty ranges. Green points:
the 35 classical Cepheids inside the bulge volume; red points: new type II bulge Cepheids
with solid classifications; black points: rest of the sample. Black points at short distances
in this figure represent candidate classical Cepheids beyond the bulge, while those at larger
distances are type II Cepheid candidates outside the bulge or objects with uncertain clas-
sification. Panel b: As panel a, but showing values computed under the assumption that
all Cepheids are of the classical type. Panel c: Ks total amplitude vs log P diagram of
classical Cepheids from the LMC (Persson et al. 2004) and the Galactic field (Monson &
Pierce 2011) (blue crosses), previously known type II Cepheids in the bulge (Soszy´nski et al.
2011, Ks amplitudes derived from VVV data) and in Galactic globular clusters (Matsunaga
et al. 2006) (red triangles), and new type II Cepheids from our study (orange triangles).
Green points show the new classical Cepheids in the inner Galaxy. Panel d: Histograms of
the discovered classical and type II Cepheid sample as a function of Galactic longitude.
11. – 11 –
0.00
0.05
0.10
0.15
0.50
1.00
1.50
2.00
0 0.5 1
Ksmagnitude(arbitraryscale)
pulsation phase
1
2
3
4
0 0.5 1
pulsation phase
1
2
3
4
5
6
7
8
9
0 0.5 1
10
11
12
13
14
15
16
17
0 0.5 1
18
19
20
21
22
23
24
25
26
27
0 0.5 1
28
29
30
31
32
33
34
35
Fig. 2.— Ks-band phase diagrams of the classical Cepheids in the inner Galaxy (on arbitrary
magnitude scale). Curves denote Fourier series fits to the data, identifiers are shown on the
left.
12. – 12 –
Y[kpc]
X [kpc]
-4
-3
-2
-1
0
1
2
3
4
0 2 4 6 8 10 12 14
4
3
2
1
0
1
2
3
4
0 2 4 6 8 10 12 14
-10-50510
L [deg.]
-2
-1
0
1
2
B[deg.]
0
0.5
1
1.5
2
A(Ks)[mag]
-10-50510
L [deg.]
-2
-1
0
1
2
B[deg.]
-10-50510
L [deg.]
-2
-1
0
1
2
B[deg.]
-10-50510
L [deg.]
-2
-1
0
1
2
B[deg.]
Fig. 3.— Top panel: positions of the classical Cepheids projected onto the Galactic plane
and their errors (green symbols), overlaid on Robert Hurt’s illustration of the Milky Way.
Orange symbols mark the Twin Cepheids (D´ek´any et al. 2015) beyond the bulge, yellow
symbols represent the classical Cepheids in the nuclear bulge (Matsunaga et al. 2011, 2015).
The Galactic bar (Gonzalez et al. 2012) is outlined by a red curve, whereas the red “x” marks
the GC (D´ek´any et al. 2013). The solid and dashed cyan lines denote the longitudinal limits
of our study and the direction of the gap in coverage towards the GC, respectively. The
bottom panel shows the classical Cepheids’ positions in Galactic coordinates, overlaid on the
VVV bulge Ks extinction map (Gonzalez et al. 2012). Black lines denote the borders of the
surveyed area.
13. – 13 –
0
1
2
3
4
5
6
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
TotalKs-bandextinction(mag)
log ( Period / days )
d = 11 kpcd = 8.3 kpcd = 6 kpc
d = 11 kpcd = 8.3 kpcd = 6 kpc
inner disk classical Cepheids
nuclear bulge classical Cepheids
Fig. 4.— Approximate VVV Survey detection limits, showing the range of pulsation periods
and foreground Ks extinction where classical Cepheids in the inner Galaxy can be detected.
Dashed lines delineate the faint detection limits, whereas solid lines convey saturation limits
for Cepheids at three different distances, illustrating the distance to the GC (D´ek´any et al.
2013) and the corresponding near and far edges of the bulge (Wegg & Gerhard 2013). Blue
points mark the classical Cepheids discovered here, blue circles show the values of classical
Cepheids in the nuclear bulge (Matsunaga et al. 2011, 2015).