This document discusses observations of the giant outflow Ou4, located near the HII region Sh 2-129. Spectroscopic observations of Ou4 reveal shock-excited gas consistent with a fast collimated outflow. Mid-infrared images show a bubble of hot dust emission inside Ou4 that corresponds to [OIII] features. The distance and properties of Ou4 are consistent with it being launched about 90,000 years ago from the young massive star cluster HR 8119, located at the center of Sh 2-129. However, the possibility that Ou4 is a planetary nebula or resulted from an eruptive event on a massive asymptotic giant branch star cannot be ruled out.
The document summarizes new HI observations of Hoag's Object obtained with the Westerbork Synthesis Radio Telescope. The key findings are:
1) The HI is detected in a ring that coincides with and extends beyond the optical ring of Hoag's Object. The entire HI structure is twice as large as the optical ring and shows a mild warp in its outer regions.
2) The HI kinematics are regular with no disturbances, providing evidence against a recent interaction being the source of the HI.
3) Two additional faint HI sources are detected near Hoag's Object, approximately 0.3 and 1 Mpc away in projected distance. At least one does
Herschel far infrared_spectroscopy_of_the_galactic_centerSérgio Sacani
The document summarizes observations from the Herschel Space Observatory of the Galactic Center region, focusing on a spectral scan toward Sagittarius A*. Key findings include:
1) Strong emission from atomic fine structure lines and rotationally excited lines of molecules like CO, H2O and HCO+ are detected.
2) The excitation of the CO ladder is consistent with either a hot isothermal gas component at 103.1 K and 104 cm-3, or a distribution of warmer gas at higher densities, with most CO at 300 K.
3) The detected molecular features suggest heating is from a combination of UV irradiation and shocks in the gas, rather than very enhanced X-ray or cosmic
1. The author measured proper motions of molecular hydrogen (H2) emission features in the Herbig-Haro 46/47 outflow system, finding tangential velocities ranging from tens to nearly 500 km/s.
2. The highest velocities were observed for H2 knots located along or near the jet/counterjet axes, while knots forming the wings of a large H2 bow shock moved more slowly.
3. Several H2 knots were found to have significantly changed luminosity over the 4-year study, indicating variability in H2 emission from young stellar object outflows for the first time.
Counterjet infrared symmetry of hh 34 and the size of the jet formation regionSérgio Sacani
The document summarizes new Spitzer IRAC images of the HH 34 outflow that detect both the southern jet and northern counterjet with comparable intensities and surprising symmetry. This removes the problem of apparent asymmetry close to the source versus large-scale symmetry. Quantitative analysis shows the counterjet knots are positioned symmetrically to within 0.11-1.57 pixels of the corresponding jet knots. This degree of symmetry implies the jet production region has a characteristic size less than 2.8 AU, providing the strongest constraint yet on the size of the region producing HH jets.
Mapping the complex_kinematics_of_l_lobjects_in_the_orion_nebulaSérgio Sacani
This document presents a study of the kinematics of two LL Orionis-type objects (LL objects) in the Orion nebula, LL 1 and LL 2, and their associated Herbig-Haro jets HH 888 and HH 505. The authors combine long-slit spectroscopic observations of the objects with proper motion measurements to construct 3D velocity maps. The maps reveal:
1) Low velocities (10-20 km/s) in the stellar bowshocks of LL 1 and LL 2, with LL 1 showing symmetric motions and LL 2 showing asymmetric motions following nebula gradients.
2) Jet knot velocities over 200 km/s near the stars declining to under 100 km/s farther out in HH 8
Alma observations of_the_hh46_47_molecular_outflowSérgio Sacani
ALMA observations of the HH 46/47 molecular outflow reveal striking differences between the blue and red lobes. The blue lobe morphology and kinematics are consistent with entrainment by a wide-angle wind, while the red lobe shows a more complex structure with evidence of entrainment by both a wide-angle wind and collimated episodic winds. Three major clumps along the red lobe axis have velocity distributions consistent with prompt entrainment by periodic mass ejection episodes occurring every few hundred years. Position-velocity cuts show velocity gradients increasing toward the outflow axis, inconsistent with outflow rotation.
This document reports the first detection of hydrogen peroxide (HOOH) in interstellar space. Four HOOH transitions were detected toward the ρ Oph A molecular cloud core, including three transitions mapped over the densest part of the core. Analysis of the line intensities using a rotation diagram method derived a HOOH rotation temperature of 22 K and column density of 8×1012 cm-2, corresponding to an abundance relative to H2 of about 1×10-10. This detection provides evidence that HOOH plays a role in oxygen and water chemistry in molecular clouds.
The document summarizes research from images taken by the New Horizons spacecraft of Charon, Pluto's largest moon. The images reveal Charon has a reddish polar cap at its north pole. Thermal models show the pole experiences long periods of extreme cold temperatures due to Charon's high obliquity and long seasons. The researchers hypothesize that methane and other volatiles escaping from Pluto's atmosphere become cold-trapped at Charon's winter pole, where they are processed by radiation into non-volatile organic compounds that remain on the surface to form the red cap. Spectral and compositional evidence supports this mechanism of seasonal accumulation of photolyzed volatiles to explain Charon's unique polar color
The document summarizes new HI observations of Hoag's Object obtained with the Westerbork Synthesis Radio Telescope. The key findings are:
1) The HI is detected in a ring that coincides with and extends beyond the optical ring of Hoag's Object. The entire HI structure is twice as large as the optical ring and shows a mild warp in its outer regions.
2) The HI kinematics are regular with no disturbances, providing evidence against a recent interaction being the source of the HI.
3) Two additional faint HI sources are detected near Hoag's Object, approximately 0.3 and 1 Mpc away in projected distance. At least one does
Herschel far infrared_spectroscopy_of_the_galactic_centerSérgio Sacani
The document summarizes observations from the Herschel Space Observatory of the Galactic Center region, focusing on a spectral scan toward Sagittarius A*. Key findings include:
1) Strong emission from atomic fine structure lines and rotationally excited lines of molecules like CO, H2O and HCO+ are detected.
2) The excitation of the CO ladder is consistent with either a hot isothermal gas component at 103.1 K and 104 cm-3, or a distribution of warmer gas at higher densities, with most CO at 300 K.
3) The detected molecular features suggest heating is from a combination of UV irradiation and shocks in the gas, rather than very enhanced X-ray or cosmic
1. The author measured proper motions of molecular hydrogen (H2) emission features in the Herbig-Haro 46/47 outflow system, finding tangential velocities ranging from tens to nearly 500 km/s.
2. The highest velocities were observed for H2 knots located along or near the jet/counterjet axes, while knots forming the wings of a large H2 bow shock moved more slowly.
3. Several H2 knots were found to have significantly changed luminosity over the 4-year study, indicating variability in H2 emission from young stellar object outflows for the first time.
Counterjet infrared symmetry of hh 34 and the size of the jet formation regionSérgio Sacani
The document summarizes new Spitzer IRAC images of the HH 34 outflow that detect both the southern jet and northern counterjet with comparable intensities and surprising symmetry. This removes the problem of apparent asymmetry close to the source versus large-scale symmetry. Quantitative analysis shows the counterjet knots are positioned symmetrically to within 0.11-1.57 pixels of the corresponding jet knots. This degree of symmetry implies the jet production region has a characteristic size less than 2.8 AU, providing the strongest constraint yet on the size of the region producing HH jets.
Mapping the complex_kinematics_of_l_lobjects_in_the_orion_nebulaSérgio Sacani
This document presents a study of the kinematics of two LL Orionis-type objects (LL objects) in the Orion nebula, LL 1 and LL 2, and their associated Herbig-Haro jets HH 888 and HH 505. The authors combine long-slit spectroscopic observations of the objects with proper motion measurements to construct 3D velocity maps. The maps reveal:
1) Low velocities (10-20 km/s) in the stellar bowshocks of LL 1 and LL 2, with LL 1 showing symmetric motions and LL 2 showing asymmetric motions following nebula gradients.
2) Jet knot velocities over 200 km/s near the stars declining to under 100 km/s farther out in HH 8
Alma observations of_the_hh46_47_molecular_outflowSérgio Sacani
ALMA observations of the HH 46/47 molecular outflow reveal striking differences between the blue and red lobes. The blue lobe morphology and kinematics are consistent with entrainment by a wide-angle wind, while the red lobe shows a more complex structure with evidence of entrainment by both a wide-angle wind and collimated episodic winds. Three major clumps along the red lobe axis have velocity distributions consistent with prompt entrainment by periodic mass ejection episodes occurring every few hundred years. Position-velocity cuts show velocity gradients increasing toward the outflow axis, inconsistent with outflow rotation.
This document reports the first detection of hydrogen peroxide (HOOH) in interstellar space. Four HOOH transitions were detected toward the ρ Oph A molecular cloud core, including three transitions mapped over the densest part of the core. Analysis of the line intensities using a rotation diagram method derived a HOOH rotation temperature of 22 K and column density of 8×1012 cm-2, corresponding to an abundance relative to H2 of about 1×10-10. This detection provides evidence that HOOH plays a role in oxygen and water chemistry in molecular clouds.
The document summarizes research from images taken by the New Horizons spacecraft of Charon, Pluto's largest moon. The images reveal Charon has a reddish polar cap at its north pole. Thermal models show the pole experiences long periods of extreme cold temperatures due to Charon's high obliquity and long seasons. The researchers hypothesize that methane and other volatiles escaping from Pluto's atmosphere become cold-trapped at Charon's winter pole, where they are processed by radiation into non-volatile organic compounds that remain on the surface to form the red cap. Spectral and compositional evidence supports this mechanism of seasonal accumulation of photolyzed volatiles to explain Charon's unique polar color
This document summarizes observations of the W49 giant molecular cloud (GMC) using the PMO 14m telescope and the Submillimeter Array (SMA). The PMO observations mapped the entire GMC in various molecular lines at scales up to 113 pc, while the SMA mosaic mapped the central star-forming region W49N at scales down to 0.5 pc. The observations are used to derive the mass structure of the GMC across all scales. The main findings are that the W49 GMC has a total gas mass of 1.1 million solar masses within 60 pc and 2x10^5 solar masses within 6 pc. The mass is distributed in a hierarchical network of filaments converging toward the central
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.
Uranus is the seventh planet from the Sun. It has the third largest planetary radius and fourth largest planetary mass. Uranus is similar in composition to Neptune and both are different than the larger gas giants like Jupiter and Saturn. Uranus has a ring system, magnetosphere, and numerous moons. William Herschel discovered Uranus in 1781 but it was originally thought to be a comet. Uranus rotates on its side with an axial tilt of 97.77 degrees. Voyager 2 is the only spacecraft to have visited Uranus, providing the first close up observations of the planet in 1986.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
A wide and collimated radio jet in 3C84 on the scale of a few hundred gravita...Sérgio Sacani
This document summarizes key findings from a study of the radio jet in galaxy 3C84 using very long baseline interferometry (VLBI) with the RadioAstron space telescope. The observations resolve the edge-brightened jet structure only 30 microarcseconds from the core, corresponding to ~350 gravitational radii. This is 10 times closer to the central engine than previous ground-based observations. The measurements show the jet has an initially wide opening angle of 130 degrees that rapidly collimates into an almost cylindrical profile out to ~8,000 gravitational radii. The wide jet observed so close to the core poses challenges for models where the jet originates from the black hole ergosphere.
Observed glacier and volatile distribution on Pluto from atmosphere–topograph...Sérgio Sacani
Pluto has a variety of surface frosts and landforms as well as a
complex atmosphere1. There is ongoing geological activity related
to the massive Sputnik Planum glacier, mostly made of nitrogen (N2)
ice mixed with solid carbon monoxide and methane2, covering the
4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planum1,3
near the anti-Charon point. The glacier has been suggested to arise
from a source region connected to the deep interior, or from a sink
collecting the volatiles released planetwide1. Thin deposits of N2
frost, however, were also detected at mid-northern latitudes and
methane ice was observed to cover most of Pluto except for the
darker, frost-free equatorial regions2. Here we report numerical
simulations of the evolution of N2, methane and carbon monoxide
on Pluto over thousands of years. The model predicts N2 ice
accumulation in the deepest low-latitude basin and the threefold
increase in atmospheric pressure that has been observed to occur
since 19884–6. This points to atmospheric–topographic processes as
the origin of Sputnik Planum’s N2 glacier. The same simulations also
reproduce the observed quantities of volatiles in the atmosphere and
show frosts of methane, and sometimes N2, that seasonally cover the
mid- and high latitudes, explaining the bright northern polar cap
reported in the 1990s7,8 and the observed ice distribution in 20152.
The model also predicts that most of these seasonal frosts should
disappear in the next decade.
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.
Alma observations of_feeding_and_feedback_in_nearby_seyfert_galaxies_outflow_...Sérgio Sacani
ALMA observations of the Seyfert 2 galaxy NGC 1433 reveal a nuclear gaseous spiral structure within a nuclear ring encircling a nuclear stellar bar. Near the nucleus, there is intense high-velocity CO emission interpreted as an AGN-driven molecular outflow. The outflow involves a molecular mass of 3.6 million solar masses and a flow rate of about 7 solar masses per year. Continuum emission at the center is likely thermal dust emission from a molecular torus expected in this Seyfert 2 galaxy. The observations probe gas dynamics within 24 parsecs of the active galactic nucleus.
Rapid formation of large dust grains in the luminous supernova SN 2010jlGOASA
This document summarizes observations of rapid dust formation in the luminous supernova SN 2010jl over multiple epochs from 26 to 868 days past peak brightness. Analysis of emission line profiles shows increasing extinction over time, indicating continuous dust formation. The extinction curve implies the presence of very large (>1 micron) dust grains. Thermal emission models suggest dust temperatures declining from 2300K to 1100K over time, requiring carbonaceous rather than silicate dust. Combined extinction and emission data indicate a dust mass of ~0.0025 solar masses at 868 days, growing rapidly and expected to reach ~0.5 solar masses by 8000 days if production continues. The results provide evidence for very efficient and rapid dust formation in the dense
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
The ASTRODEEP Frontier Fields catalogues II. Photometric redshifts and rest f...Sérgio Sacani
This document describes a public release of photometric redshifts and galaxy properties from multi-wavelength data in the Abell-2744 and MACS-J0416 galaxy cluster fields observed as part of the Frontier Fields program. Photometric redshifts were estimated using six different methods and have an accuracy of 3-5%. Accounting for gravitational lensing magnification, the H-band number counts agree with CANDELS at bright magnitudes but extend to intrinsically fainter galaxies of H=32-33. The Frontier Fields data allow probing galaxy stellar masses 0.5-1.5 dex lower than in wide fields, including sources with masses of 107-108 solar masses at z>5. Star formation rates can be detected 1
Detectcion of noble_gas_molecular_ion_arh_in_the_crab_nebulaSérgio Sacani
Scientists detected emission lines from the ionized argon hydride (36ArH+) molecule in spectra of the Crab Nebula obtained with the Herschel Space Observatory. The detection of 36ArH+ confirms that argon originated from explosive nucleosynthesis during the core-collapse supernova that created the Crab Nebula. The likely excitation mechanism is electron collisions in partially ionized regions with electron densities of a few hundred per cubic centimeter. This is the first detection of a noble gas molecule in space.
One tenth solar_abundances_along_the_body_of-the_streamSérgio Sacani
This document summarizes a study that analyzed spectra from four background quasars to measure the chemical abundances along the Magellanic Stream. Two key findings are:
1) The sightlines toward RBS 144 and NGC 7714 yielded metallicities of around 0.1 times the solar value, indicating a uniform low abundance along the main body of the Stream. This supports models where the Stream was stripped from the SMC around 1-2.5 billion years ago when the SMC had a metallicity of around 0.1 solar.
2) A higher metallicity of around 0.5 solar was found in the inner Stream toward Fairall 9, sampling a filament traced to the LMC. This shows the bifurc
Galaxy dynamics and the mass density of the universeSérgio Sacani
Dynamical evidence accumulated over the
past 20 years has convinced astronomers that luminous matter
in a spiral galaxy constitutes no more than 10% of the mass of
a galaxy. An additional 90% is inferred by its gravitational
effect on luminous material. Here I review recent observations
concerning the distribution of luminous and nonluminous
matter in the Milky Way, in galaxies, and in galaxy clusters.
Observations of neutral hydrogen disks, some extending in
radius several times the optical disk, confirm that a massive
dark halo is a major component of virtually every spiral. A
recent surprise has been the discovery that stellar and gas
motions in ellipticals are enormously complex. To date, only for
a few spheroidal galaxies do the velocities extend far enough to
probe the outer mass distribution. But the diverse kinematics
of inner cores, peripheral to deducing the overall mass distribution,
offer additional evidence that ellipticals have acquired
gas-rich systems after initial formation. Dynamical results are
consistent with a low-density universe, in which the required
dark matter could be baryonic. On smallest scales of galaxies
[10 kiloparsec (kpc); H. = 50 kmsec'lmegaparsec'11 the
luminous matter constitutes only 1% of the closure density. On
scales greater than binary galaxies (i.e., .100 kpc) all systems
indicate a density -10% of the closure density, a density
consistent with the low baryon density in the universe. If
large-scale motions in the universe require a higher mass
density, these motions would constitute the first dynamical
evidence for nonbaryonic matter in a universe of higher
density.
A candidate redshift z < 10 galaxy and rapid changes in that population at...Sérgio Sacani
The document summarizes the findings of a study searching for galaxies at redshift z > 10 using deep imaging data from the Hubble Ultra Deep Field. The key points are:
1) The study detects one possible galaxy candidate at z ~ 10.3, the earliest galaxy reported to date.
2) Regardless of detections, the star formation rate density is found to be much smaller (~10%) at z ~ 10 than just 200 million years later at z ~ 8, demonstrating rapid galaxy build-up in the first 500 million years.
3) The 100-200 million years before z ~ 10 appears to be a crucial phase in the early assembly of galaxies.
Observations of gas_flows_inside_a_protoplanetary_gapSérgio Sacani
1) ALMA observations of the protoplanetary disk around HD 142527 reveal diffuse CO gas and denser HCO+ filaments inside the dust gap.
2) The HCO+ filaments extend from the outer disk towards the inner disk and star, indicating gas flowing across the gap.
3) Estimates of the gas flow rate through the filaments are sufficient to sustain the observed rate of accretion onto the star, supporting the interpretation that the filaments are planet-induced gap-crossing accretion streams.
A rare case of FR I interaction with a hot X-ray bridge in the A2384 galaxy c...Sérgio Sacani
Clusters of varying mass ratios can merge and the process significantly disturbs
the cluster environments and alters their global properties. Active radio galaxies are
another phenomenon that can also affect cluster environments. Radio jets can interact
with the intra-cluster medium (ICM) and locally affect its properties. Abell 2384
(hereafter A2384) is a unique system that has a dense, hot X-ray filament or bridge
connecting the two unequal mass clusters A2384(N) and A2384(S). The analysis of its
morphology suggests that A2384 is a post-merger system where A2384(S) has already
interacted with the A2384(N), and as a result hot gas has been stripped over a ∼ 1
Mpc region between the two bodies. We have obtained its 325 MHz GMRT data,
and we detected a peculiar FR I type radio galaxy which is a part of the A2384(S).
One of its radio lobes interacts with the hot X-ray bridge and pushes the hot gas in
the opposite direction. This results in displacement in the bridge close to A2384(S).
Based on Chandra and XMM-Newton X-ray observations, we notice a temperature and
entropy enhancement at the radio lobe-X-ray plasma interaction site, which further
suggests that the radio lobe is changing thermal plasma properties. We have also
studied the radio properties of the FR I radio galaxy, and found that the size and
radio luminosity of the interacting north lobe of the FR I galaxy are lower than those
of the accompanying south lobe.
Detection of highvelocity_material_from_the_win_wind_collision_zone_of_eta_ca...Sérgio Sacani
This document reports on observations of the Eta Carinae binary system using infrared spectroscopy from 2008-2009 and archival ultraviolet and optical data. It detects high-velocity material of up to -1900 km/s in He I absorption during the 2009 periastron passage, as well as up to -2100 km/s in Si IV absorption in earlier data. Lower ionization lines only show absorption up to -1200 km/s, indicating the high-velocity material is faster and more ionized than the primary star's wind. Additional observations over multiple cycles detect high-velocity He I absorption near periastron. The high-velocity material likely originates in the wind collision zone 15-45 AU from the primary star.
This document summarizes observations of the W49 giant molecular cloud (GMC) using the PMO 14m telescope and the Submillimeter Array (SMA). The PMO observations mapped the entire GMC in various molecular lines at scales up to 113 pc, while the SMA mosaic mapped the central star-forming region W49N at scales down to 0.5 pc. The observations are used to derive the mass structure of the GMC across all scales. The main findings are that the W49 GMC has a total gas mass of 1.1 million solar masses within 60 pc and 2x10^5 solar masses within 6 pc. The mass is distributed in a hierarchical network of filaments converging toward the central
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.
Uranus is the seventh planet from the Sun. It has the third largest planetary radius and fourth largest planetary mass. Uranus is similar in composition to Neptune and both are different than the larger gas giants like Jupiter and Saturn. Uranus has a ring system, magnetosphere, and numerous moons. William Herschel discovered Uranus in 1781 but it was originally thought to be a comet. Uranus rotates on its side with an axial tilt of 97.77 degrees. Voyager 2 is the only spacecraft to have visited Uranus, providing the first close up observations of the planet in 1986.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
A wide and collimated radio jet in 3C84 on the scale of a few hundred gravita...Sérgio Sacani
This document summarizes key findings from a study of the radio jet in galaxy 3C84 using very long baseline interferometry (VLBI) with the RadioAstron space telescope. The observations resolve the edge-brightened jet structure only 30 microarcseconds from the core, corresponding to ~350 gravitational radii. This is 10 times closer to the central engine than previous ground-based observations. The measurements show the jet has an initially wide opening angle of 130 degrees that rapidly collimates into an almost cylindrical profile out to ~8,000 gravitational radii. The wide jet observed so close to the core poses challenges for models where the jet originates from the black hole ergosphere.
Observed glacier and volatile distribution on Pluto from atmosphere–topograph...Sérgio Sacani
Pluto has a variety of surface frosts and landforms as well as a
complex atmosphere1. There is ongoing geological activity related
to the massive Sputnik Planum glacier, mostly made of nitrogen (N2)
ice mixed with solid carbon monoxide and methane2, covering the
4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planum1,3
near the anti-Charon point. The glacier has been suggested to arise
from a source region connected to the deep interior, or from a sink
collecting the volatiles released planetwide1. Thin deposits of N2
frost, however, were also detected at mid-northern latitudes and
methane ice was observed to cover most of Pluto except for the
darker, frost-free equatorial regions2. Here we report numerical
simulations of the evolution of N2, methane and carbon monoxide
on Pluto over thousands of years. The model predicts N2 ice
accumulation in the deepest low-latitude basin and the threefold
increase in atmospheric pressure that has been observed to occur
since 19884–6. This points to atmospheric–topographic processes as
the origin of Sputnik Planum’s N2 glacier. The same simulations also
reproduce the observed quantities of volatiles in the atmosphere and
show frosts of methane, and sometimes N2, that seasonally cover the
mid- and high latitudes, explaining the bright northern polar cap
reported in the 1990s7,8 and the observed ice distribution in 20152.
The model also predicts that most of these seasonal frosts should
disappear in the next decade.
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.
Alma observations of_feeding_and_feedback_in_nearby_seyfert_galaxies_outflow_...Sérgio Sacani
ALMA observations of the Seyfert 2 galaxy NGC 1433 reveal a nuclear gaseous spiral structure within a nuclear ring encircling a nuclear stellar bar. Near the nucleus, there is intense high-velocity CO emission interpreted as an AGN-driven molecular outflow. The outflow involves a molecular mass of 3.6 million solar masses and a flow rate of about 7 solar masses per year. Continuum emission at the center is likely thermal dust emission from a molecular torus expected in this Seyfert 2 galaxy. The observations probe gas dynamics within 24 parsecs of the active galactic nucleus.
Rapid formation of large dust grains in the luminous supernova SN 2010jlGOASA
This document summarizes observations of rapid dust formation in the luminous supernova SN 2010jl over multiple epochs from 26 to 868 days past peak brightness. Analysis of emission line profiles shows increasing extinction over time, indicating continuous dust formation. The extinction curve implies the presence of very large (>1 micron) dust grains. Thermal emission models suggest dust temperatures declining from 2300K to 1100K over time, requiring carbonaceous rather than silicate dust. Combined extinction and emission data indicate a dust mass of ~0.0025 solar masses at 868 days, growing rapidly and expected to reach ~0.5 solar masses by 8000 days if production continues. The results provide evidence for very efficient and rapid dust formation in the dense
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
The ASTRODEEP Frontier Fields catalogues II. Photometric redshifts and rest f...Sérgio Sacani
This document describes a public release of photometric redshifts and galaxy properties from multi-wavelength data in the Abell-2744 and MACS-J0416 galaxy cluster fields observed as part of the Frontier Fields program. Photometric redshifts were estimated using six different methods and have an accuracy of 3-5%. Accounting for gravitational lensing magnification, the H-band number counts agree with CANDELS at bright magnitudes but extend to intrinsically fainter galaxies of H=32-33. The Frontier Fields data allow probing galaxy stellar masses 0.5-1.5 dex lower than in wide fields, including sources with masses of 107-108 solar masses at z>5. Star formation rates can be detected 1
Detectcion of noble_gas_molecular_ion_arh_in_the_crab_nebulaSérgio Sacani
Scientists detected emission lines from the ionized argon hydride (36ArH+) molecule in spectra of the Crab Nebula obtained with the Herschel Space Observatory. The detection of 36ArH+ confirms that argon originated from explosive nucleosynthesis during the core-collapse supernova that created the Crab Nebula. The likely excitation mechanism is electron collisions in partially ionized regions with electron densities of a few hundred per cubic centimeter. This is the first detection of a noble gas molecule in space.
One tenth solar_abundances_along_the_body_of-the_streamSérgio Sacani
This document summarizes a study that analyzed spectra from four background quasars to measure the chemical abundances along the Magellanic Stream. Two key findings are:
1) The sightlines toward RBS 144 and NGC 7714 yielded metallicities of around 0.1 times the solar value, indicating a uniform low abundance along the main body of the Stream. This supports models where the Stream was stripped from the SMC around 1-2.5 billion years ago when the SMC had a metallicity of around 0.1 solar.
2) A higher metallicity of around 0.5 solar was found in the inner Stream toward Fairall 9, sampling a filament traced to the LMC. This shows the bifurc
Galaxy dynamics and the mass density of the universeSérgio Sacani
Dynamical evidence accumulated over the
past 20 years has convinced astronomers that luminous matter
in a spiral galaxy constitutes no more than 10% of the mass of
a galaxy. An additional 90% is inferred by its gravitational
effect on luminous material. Here I review recent observations
concerning the distribution of luminous and nonluminous
matter in the Milky Way, in galaxies, and in galaxy clusters.
Observations of neutral hydrogen disks, some extending in
radius several times the optical disk, confirm that a massive
dark halo is a major component of virtually every spiral. A
recent surprise has been the discovery that stellar and gas
motions in ellipticals are enormously complex. To date, only for
a few spheroidal galaxies do the velocities extend far enough to
probe the outer mass distribution. But the diverse kinematics
of inner cores, peripheral to deducing the overall mass distribution,
offer additional evidence that ellipticals have acquired
gas-rich systems after initial formation. Dynamical results are
consistent with a low-density universe, in which the required
dark matter could be baryonic. On smallest scales of galaxies
[10 kiloparsec (kpc); H. = 50 kmsec'lmegaparsec'11 the
luminous matter constitutes only 1% of the closure density. On
scales greater than binary galaxies (i.e., .100 kpc) all systems
indicate a density -10% of the closure density, a density
consistent with the low baryon density in the universe. If
large-scale motions in the universe require a higher mass
density, these motions would constitute the first dynamical
evidence for nonbaryonic matter in a universe of higher
density.
A candidate redshift z < 10 galaxy and rapid changes in that population at...Sérgio Sacani
The document summarizes the findings of a study searching for galaxies at redshift z > 10 using deep imaging data from the Hubble Ultra Deep Field. The key points are:
1) The study detects one possible galaxy candidate at z ~ 10.3, the earliest galaxy reported to date.
2) Regardless of detections, the star formation rate density is found to be much smaller (~10%) at z ~ 10 than just 200 million years later at z ~ 8, demonstrating rapid galaxy build-up in the first 500 million years.
3) The 100-200 million years before z ~ 10 appears to be a crucial phase in the early assembly of galaxies.
Observations of gas_flows_inside_a_protoplanetary_gapSérgio Sacani
1) ALMA observations of the protoplanetary disk around HD 142527 reveal diffuse CO gas and denser HCO+ filaments inside the dust gap.
2) The HCO+ filaments extend from the outer disk towards the inner disk and star, indicating gas flowing across the gap.
3) Estimates of the gas flow rate through the filaments are sufficient to sustain the observed rate of accretion onto the star, supporting the interpretation that the filaments are planet-induced gap-crossing accretion streams.
A rare case of FR I interaction with a hot X-ray bridge in the A2384 galaxy c...Sérgio Sacani
Clusters of varying mass ratios can merge and the process significantly disturbs
the cluster environments and alters their global properties. Active radio galaxies are
another phenomenon that can also affect cluster environments. Radio jets can interact
with the intra-cluster medium (ICM) and locally affect its properties. Abell 2384
(hereafter A2384) is a unique system that has a dense, hot X-ray filament or bridge
connecting the two unequal mass clusters A2384(N) and A2384(S). The analysis of its
morphology suggests that A2384 is a post-merger system where A2384(S) has already
interacted with the A2384(N), and as a result hot gas has been stripped over a ∼ 1
Mpc region between the two bodies. We have obtained its 325 MHz GMRT data,
and we detected a peculiar FR I type radio galaxy which is a part of the A2384(S).
One of its radio lobes interacts with the hot X-ray bridge and pushes the hot gas in
the opposite direction. This results in displacement in the bridge close to A2384(S).
Based on Chandra and XMM-Newton X-ray observations, we notice a temperature and
entropy enhancement at the radio lobe-X-ray plasma interaction site, which further
suggests that the radio lobe is changing thermal plasma properties. We have also
studied the radio properties of the FR I radio galaxy, and found that the size and
radio luminosity of the interacting north lobe of the FR I galaxy are lower than those
of the accompanying south lobe.
Detection of highvelocity_material_from_the_win_wind_collision_zone_of_eta_ca...Sérgio Sacani
This document reports on observations of the Eta Carinae binary system using infrared spectroscopy from 2008-2009 and archival ultraviolet and optical data. It detects high-velocity material of up to -1900 km/s in He I absorption during the 2009 periastron passage, as well as up to -2100 km/s in Si IV absorption in earlier data. Lower ionization lines only show absorption up to -1200 km/s, indicating the high-velocity material is faster and more ionized than the primary star's wind. Additional observations over multiple cycles detect high-velocity He I absorption near periastron. The high-velocity material likely originates in the wind collision zone 15-45 AU from the primary star.
Artigo descreve a descoberta dos astrônomos de 4 imagens de uma supernova geradas pelo efeito de lente gravitacional e formando o raro padrão da Cruz de Einstein.
Spitzer as microlens_parallax_satellite_mass_measurement_for_exoplanet_and_hi...Sérgio Sacani
This document summarizes a study using Spitzer and ground-based observations to measure the microlens parallax vector πE for the first time for a planetary microlensing event, OGLE-2014-BLG-0124L. The πE measurement allows the mass and distance of the planet and its host star to be determined. Spitzer observations provided a 2.5% precision measurement of πE, substantially improving upon the 22% precision from ground data alone. The planet has a mass of about 0.5 Jupiter masses and orbits a star of about 0.7 solar masses at a projected distance of about 3.1 AU.
The behaviour of_dark_matter_associated_with_4_bright_cluster_galaxies_in_the...Sérgio Sacani
The document presents new Hubble Space Telescope imaging and Very Large Telescope integral-field spectroscopy of galaxy cluster Abell 3827. It finds that each of the four central galaxies in the cluster's 10 kpc core retains an associated massive dark matter halo. At least one galaxy is offset from its dark matter halo, with an offset of 1.62+0.50−0.47 kpc, within the uncertainties of mass modeling and statistical errors. If interpreted as evidence for self-interacting dark matter, this offset implies a dark matter self-interaction cross-section of (1.7 ± 0.7)×10−4 cm2/g.
Wind from the_black_hole_accretion_disk_driving_a_molecular_outflow_in_an_act...Sérgio Sacani
Artigo descreve estudo inédito que mostra que os ventos gerados pelos buracos negros nos centros das galáxias pode acabar com o processo de formação de estrelas nas galáxias hospedeiras.
The non gravitational_interactions_of_dark_matter_in_colliding_galaxy_clustersSérgio Sacani
1) The document analyzes 72 galaxy cluster collisions observed with Hubble and Chandra telescopes to test theories of non-gravitational dark matter interactions.
2) It detects the existence of dark matter at 7.6 sigma significance by comparing the positions of dark mass concentrations to stars and gas.
3) Combining measurements from all collisions, it constrains the dark matter self-interaction cross-section to be less than 0.47 cm^2/g (95% confidence level), ruling out some proposed dark matter models with stronger interactions.
Know the star_know_the_planet_discovery_of_l_ate_type_companions_to_two_exopl...Sérgio Sacani
This document summarizes the discovery of additional late-type stellar companions to two exoplanet host stars, HD 2638 and 30 Ari B, using adaptive optics imaging. For both systems, the companions were found to share common proper motion with the primaries, indicating they are physically associated. The estimated orbital periods of the new companions are 130 years for HD 2638 and 80 years for 30 Ari B. This makes 30 Ari B the second confirmed quadruple star system known to host an exoplanet. The discoveries provide additional examples of how binary companions can influence exoplanet dynamics and formation.
Old supernova dust_factory_revealed_at_galactic_centerSérgio Sacani
The document appears to be a research paper containing scientific data and analysis across multiple pages. It includes tables of data with numerical values and variables. The paper examines different regions and calculates total mass and ratios of mass between variables. Graphs and statistical analysis are referenced but not included.
Saturns fast spin_determined_from_its_gravitational_field_and_oblatenessSérgio Sacani
ARtigo descreve o novo método usado para determinar com precisão o período de rotação do planeta Saturno. Uma das grandes questões da astronomia. De acordo com o artigo o período de rotação de Saturno é de 10 horas 32 minutos e 45 segundos (+/- 46 segundos).
The computational limit_to_quantum_determinism_and_the_black_hole_information...Sérgio Sacani
The document discusses the limits of quantum determinism and its implications for the black hole information paradox. It argues that assuming the Strong Exponential Time Hypothesis (SETH), which conjectures that known algorithms for solving computational NP-complete problems are optimal, quantum determinism cannot generally be used to predict the future state of a physical system, especially macroscopic systems. This is because even if the initial state were known precisely, it may be impossible in the real world to solve the system's Schrodinger equation in time to predict its final state before an observation. The breakdown of quantum determinism in black hole formation and evaporation may support SETH and help resolve the black hole information paradox.
High resolution image_of_a_cometary_globule_in_helix_nebulaSérgio Sacani
This document summarizes high-resolution observations of a cometary globule in the Helix Nebula made using the IRAM interferometer and SOFI infrared camera. The observations image the globule in the CO J=1-0 line and H2 v=1-0 S(1) line. They reveal that the head of the globule appears as a narrow peak in CO emission outlined by limb-brightened H2 emission facing the central star. Emission from both molecules extends into the tail region, providing new constraints on globule structure and evolution.
Hot white dwarfs and pre-white dwarfs discovered with SALTSérgio Sacani
The Southern African Large Telescope survey of helium-rich hot subdwarfs aims to explore evolutionary pathways among
groups of highly evolved stars. The selection criteria mean that several hot white dwarfs and related objects have also been
included. This paper reports the discovery and analysis of eight new very hot white dwarf and pre-white dwarf stars with effective
temperatures exceeding 100 000 K. They include two PG1159 stars, one DO white dwarf, three O(He), and two O(H) stars. One
of the O(H) stars is the central star of a newly discovered planetary nebula, and the other is the hottest ‘naked’ O(H) star. Both
of the PG1159 stars are GW Vir variables, one being the hottest GW Vir star measured and a crucial test for pulsation stability
models. The DO white dwarf is also the hottest in its class.
Beyond the disk: EUV coronagraphic observations of the Extreme Ultraviolet Im...Sérgio Sacani
Most observations of the solar corona beyond 2 R consist of broadband visible light imagery carried out with coronagraphs.
The associated diagnostics mainly consist of kinematics and derivations of the electron number density. While the measurement of the
properties of emission lines can provide crucial additional diagnostics of the coronal plasma (temperatures, velocities, abundances,
etc.), these types of observations are comparatively rare. In visible wavelengths, observations at these heights are limited to total
eclipses. In the ultraviolet (UV) to extreme UV (EUV) range, very few additional observations have been achieved since the pioneering
results of the Ultraviolet Coronagraph Spectrometer (UVCS).
Aims. One of the objectives of the Full Sun Imager (FSI) channel of the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter
mission has been to provide very wide field-of-view EUV diagnostics of the morphology and dynamics of the solar atmosphere in
temperature regimes that are typical of the lower transition region and of the corona.
Methods. FSI carries out observations in two narrowbands of the EUV spectrum centered on 17.4 nm and 30.4 nm that are dominated,
respectively, by lines of Fe ix/x (formed in the corona around 1 MK) and by the resonance line of He ii (formed around 80 kK in the
lower transition region). Unlike previous EUV imagers, FSI includes a moveable occulting disk that can be inserted in the optical path
to reduce the amount of instrumental stray light to a minimum.
Results. FSI detects signals at 17.4 nm up to the edge of its field of view (7 R), which is about twice further than was previously
possible. Operation at 30.4 nm are for the moment compromised by an as-yet unidentified source of stray light. Comparisons with
observations by the LASCO and Metis coronagraphs confirm the presence of morphological similarities and differences between the
broadband visible light and EUV emissions, as documented on the basis of prior eclipse and space-based observations.
Conclusions. The very-wide-field observations of FSI out to about 3 and 7 R, without and with the occulting disk, respectively, are
paving the way for future dedicated instruments.
The document summarizes findings from the Microwave Instrument on the Rosetta Orbiter (MIRO) regarding the subsurface properties and early activity of comet 67P/Churyumov-Gerasimenko. Key points:
- MIRO detected water vapor emissions from the comet beginning in early June 2014 and measured the total water production rate, which varied from 0.3 kg/s to 1.2 kg/s between June and August.
- Water outgassing displayed periodic variations correlated with the comet's 12.4-hour rotation period and seemed to originate primarily from the comet's "neck" region.
- Subsurface temperatures measured by MIRO showed seasonal and diurnal variations, indicating radiation
Dust in the_polar_region_as_a_major_contributor_to_the_infrared_emission_of_a...Sérgio Sacani
The mid-infrared emission of the active galactic nucleus NGC 3783 was observed using interferometry over multiple epochs, providing dense coverage of position angles and baselines. The emission was found to be strongly elongated along a position angle of -52 degrees, closely aligned with the polar axis orientation of -45 degrees. The half-light radii were measured to be 20.0 mas by 6.7 mas, corresponding to an axis ratio of 3:1. This implies that 60-90% of the 8-13 micron emission is from the polar-elongated component. The observations support a scenario where the majority of mid-infrared emission in Seyfert galaxies originates from a dusty wind in the polar region,
This document summarizes an observational study of 92 southern stars using near-infrared interferometry to search for hot exozodiacal dust. The study found an 11% detection rate of bright dust, with 9 confirmed and 3 tentative detections. The detection rate decreased for later spectral type stars and increased with stellar age. No correlation was found between the presence of cold dust and hot dust. Spectral analysis suggested the dust is extremely hot or emission is dominated by scattered light in most cases. The results provide insights into the prevalence and properties of dust near the habitable zones of other stars.
1. VFTS 682 is a very massive star located 29 pc in projection from the young massive cluster R136 in the Tarantula Nebula of the LMC.
2. Spectral modeling finds it has an unusually high luminosity of log(L/L) = 6.5, corresponding to a present-day mass of ~150 solar masses.
3. Its isolation and mass pose the question of whether it formed in situ, which would profoundly impact theories of massive star formation, or if it was ejected from R136, making it the most massive runaway star known.
Herschel galactic plane_survey_the_global_distribution_of_ism_gas_componnentSérgio Sacani
This document summarizes a study using Herschel observations of the [C ii] 158μm line to analyze the distribution of different gas components in the Milky Way galaxy. The observations provide high-resolution maps of [C ii] emission across the Galactic plane. By comparing these maps to observations of HI, CO, and other tracers, the study finds that [C ii] emission is associated with spiral arms between 4-10 kpc from the Galactic center. It estimates that [C ii] traces dense photon-dominated regions (47%), CO-dark H2 gas (28%), cold atomic gas (21%), and ionized gas (4%). The study also analyzes the distribution of cold neutral medium versus
Xray and protostars_in_the_trifid_nebulaSérgio Sacani
The document summarizes X-ray observations of the Trifid Nebula using ROSAT and ASCA. ROSAT images revealed around a dozen X-ray sources in the nebula, including the bright O7 star HD 164492 that provides much of the ionization. Ten X-ray sources were correlated with near-infrared sources identified as young stars or protostars. ASCA spectroscopy of the brightest source showed hard X-ray emission up to 10 keV including an iron K line, best fit with a two-temperature thermal model and absorption. The hotter component's temperature is unusually high and may originate from interaction with another object or protostellar flares.
Imaging the Inner Astronomical Unit of the Herbig Be Star HD 190073Sérgio Sacani
The inner regions of protoplanetary disks host many complex physical processes such as star–disk interactions,
magnetic fields, planet formation, and the migration of new planets. To study directly this region requires
milliarcsecond angular resolution, beyond the diffraction limit of the world's largest optical telescopes and even too
small for the millimeter-wave interferometer Atacama Large Millimeter/submillimeter Array (ALMA). However,
we can use infrared interferometers to image the inner astronomical unit. Here, we present new results from the
CHARA and VLTI arrays for the young and luminous Herbig Be star HD 190073. We detect a sub-astronomical
unit (sub-AU) cavity surrounded by a ring-like structure that we interpret as the dust destruction front. We model
the shape with six radial profiles, three symmetric and three asymmetric, and present a model-free image
reconstruction. All the models are consistent with a near face-on disk with an inclination 20°, and we measure an
average ring radius of 1.4 ± 0.2 mas (1.14 au). Around 48% of the total flux comes from the disk with 15% of that
emission appearing to emerge from inside the inner rim. The cause of emission is still unclear, perhaps due to
different dust grain compositions or gas emission. The skewed models and the imaging point to an off-center star,
possibly due to binarity. Our image shows sub-AU structure, which seems to move between the two epochs
inconsistently with Keplerian motion and we discuss possible explanations for this apparent change.
ALMA Observations of the Extraordinary Carina Pillars: A Complementary SampleSérgio Sacani
We present a study of six dusty and gaseous pillars (containing the HH 1004 and HH 1010 objects)
and globules (that contain the HH 666, HH 900, HH 1006, and HH 1066 objects) localized in the Carina
nebula using sensitive and high angular resolution (∼0.3′′) Atacama Large Millimeter/Sub-millimeter
Array (ALMA) observations. This is a more extensive study that the one presented in Cortes-Rangel
et al. (2020). As in this former study, we also analyzed the 1.3 mm continuum emission and C18O(2−1),
N2D+(3−2) and 12CO(2−1) spectral lines. These new observations revealed the molecular outflows
emanating from the pillars, the dusty envelopes+disks that are exciting them, and the extended HH
objects far from their respective pillars. We reveal that the masses of the disks+envelopes are in a
range of 0.02 to 0.38 M⊙, and those for the molecular outflows are of the order of 10−3 M⊙, which
suggests that their exciting sources might be low- or intermediate-mass protostars as already revealed
in recent studies at infrared and submillimeter bands. In the regions associated with the objects HH
900 and HH 1004, we report multiple millimeter continuum sources, from where several molecular
outflows emanate.
This document summarizes research on determining temperatures, luminosities, and masses of the coldest known brown dwarfs. The key findings are:
1) Precise distances were measured for a sample of late-T and Y dwarfs using Spitzer Space Telescope astrometry, allowing accurate calculation of absolute fluxes, luminosities, and temperatures.
2) Y0 dwarfs were found to have temperatures of 400-450 K, significantly warmer than previous estimates, and masses of 5-20 times Jupiter's mass.
3) While having similar temperatures, Y dwarfs showed diverse spectral energy distributions, suggesting temperature alone does not determine spectra. Physical properties like gravity, clouds and chemistry also influence spectra.
This document summarizes the discovery of two planetary companions orbiting the metal-poor star HIP 11952 based on radial velocity measurements. The star HIP 11952 was observed over a period of 16 months using the FEROS spectrograph. Analysis of the spectra revealed periodic radial velocity variations of 6.95 days and 290 days, indicating the presence of two planets with minimum masses of 0.78 MJup and 2.93 MJup orbiting at 0.07 AU and 0.81 AU, respectively. HIP 11952 is a metal-poor star with [Fe/H] of -1.95, making it one of the few known systems with planets orbiting a star with such low metallicity
The document analyzes Spitzer Infrared Spectrograph (IRS) observations of warm molecular hydrogen (H2) gas in M51. It finds that the six H2 lines observed have distinct emission distributions across the galaxy. Lower J lines like H2 S(0) peak in the spiral arms, while higher J lines like H2 S(3) peak at the nucleus. The observations are used to model the H2 excitation temperature and mass in a warm (100-300 K) and hot (400-1000 K) phase. The warm gas peaks at 11 M_sun/pc^2 in the spiral arms, while the hot gas peaks at 0.24 M_sun/pc^2 at the
The document summarizes observations of water in Jupiter's stratosphere made by the Herschel Space Observatory. Herschel/HIFI obtained a 5x5 pixel map of a water emission line, finding that water decreases from southern to northern latitudes. Herschel/PACS also obtained water maps. Infrared Telescope Facility observations of methane were used to constrain stratospheric temperatures. The latitudinal distribution of water cannot be explained by temperature variations and rules out interplanetary dust as the main water source. The observations provide evidence that Jupiter's stratospheric water originated from the 1994 Shoemaker-Levy 9 comet impacts.
The document summarizes Spitzer observations of the supernova remnant IC 443. The MIPS images show the remnant's morphology in great detail, resembling a shell or loop. The dust temperature ranges from 18-30 K based on the 70/160um ratio. IRS spectroscopy confirms shock-excited atomic and molecular emission, with shock velocities of 60-90 km/s. H2 excitation diagrams show temperatures of 300-600 K and column densities varying across the remnant.
Discovery of a_probable_4_5_jupiter_mass_exoplanet_to_hd95086_by_direct_imagingSérgio Sacani
The document reports the discovery of a probable 4-5 Jupiter-mass exoplanet orbiting the young star HD 95086. Deep imaging observations using VLT/NaCo detected a faint source at a separation of 56 AU from the star. Follow-up observations over more than a year found the source to be co-moving with the star, suggesting it is bound. Its luminosity corresponds to a predicted mass of 4-5 Jupiter masses, making it the lowest mass exoplanet directly imaged around a star. If confirmed, this discovery could provide insights into giant planet formation and evolution.
A population of_fast_radio_bursts_ar_cosmological_distancesSérgio Sacani
1) Four fast radio bursts (FRBs) lasting only a few milliseconds were detected in a radio survey of the high Galactic latitude sky.
2) The bursts' properties indicate they are of celestial rather than terrestrial origin and likely originate from cosmological distances of 0.5 to 3 billion light years.
3) No coincident x-ray or gamma-ray signals were found associated with the bursts. Characterizing the population of FRBs could help determine the baryonic content of the universe.
This document summarizes a blind HI survey of the southern Milky Way zone of avoidance conducted with the Parkes radio telescope. The survey detected 883 galaxies at Galactic longitudes 212° < l < 36° and latitudes |b| < 5° to a sensitivity of 6 mJy per 27 km/s channel. Fifty-one percent of detections had known optical/near-infrared counterparts, while 27% had new counterparts identified. The survey delineated large-scale structures in the Puppis and Great Attractor regions for the first time. Several newly identified galaxy concentrations and clusters were revealed that help trace the Great Attractor Wall.
GOALS-JWST: Unveiling Dusty Compact Sources in the Merging Galaxy IIZw096Sérgio Sacani
We have used the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) to obtain the first
spatially resolved, mid-infrared images of IIZw096, a merging luminous infrared galaxy (LIRG) at z = 0.036.
Previous observations with the Spitzer Space Telescope suggested that the vast majority of the total IR luminosity
(LIR) of the system originated from a small region outside of the two merging nuclei. New observations with
JWST/MIRI now allow an accurate measurement of the location and luminosity density of the source that is
responsible for the bulk of the IR emission. We estimate that 40%–70% of the IR bolometric luminosity, or
3–5 × 1011 Le, arises from a source no larger than 175 pc in radius, suggesting a luminosity density of at least
3–5 × 1012 Le kpc−2
. In addition, we detect 11 other star-forming sources, five of which were previously
unknown. The MIRI F1500W/F560W colors of most of these sources, including the source responsible for the
bulk of the far-IR emission, are much redder than the nuclei of local LIRGs. These observations reveal the power
of JWST to disentangle the complex regions at the hearts of merging, dusty galaxies.
Similar to Gas physical conditions_and_kinematics_of_the_giant_outflow_ou4 (20)
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.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
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.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
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.
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.
GBSN - Biochemistry (Unit 6) Chemistry of Proteins
Gas physical conditions_and_kinematics_of_the_giant_outflow_ou4
1. Gas physical conditions and kinematics of the giant
outflow Ou4
Romano Corradi, Nicolas Grosso, Agn`es Acker, Robert Greimel, Patrick
Guillout
To cite this version:
Romano Corradi, Nicolas Grosso, Agn`es Acker, Robert Greimel, Patrick Guillout. Gas physical
conditions and kinematics of the giant outflow Ou4. Accepted for publication in Astronomy &
Astrophysics. 2014. <hal-01022286>
HAL Id: hal-01022286
https://hal.archives-ouvertes.fr/hal-01022286
Submitted on 10 Jul 2014
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2. Astronomy & Astrophysics manuscript no. ou4_high_res c ESO 2014
July 9, 2014
Gas physical conditions and kinematics of the giant outflow Ou4
Romano L.M. Corradi1, 2, , Nicolas Grosso3, , Agnès Acker3, Robert Greimel4, and Patrick Guillout3
1
Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain e-mail: rcorradi@iac.es
2
Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
3
Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, 67000 Strasbourg,
France
4
IGAM, Institut für Physik, Universität Graz, Universitätsplatz 5/II, A-8010 Graz, Austria
ABSTRACT
Context. Ou4 is a recently discovered bipolar outflow with a projected size of more than one degree in the plane of the sky. It is
apparently centred on the young stellar cluster – whose most massive representative is the triple system HR 8119 – inside the H ii
region Sh 2-129. The driving source, the nature, and the distance of Ou4 are not known.
Aims. The basic properties of Ou4 and its environment are investigated in order to shed light on the origin of this remarkable outflow.
Methods. Deep narrow-band imagery of the whole nebula at arcsecond resolution was obtained to study its detailed morphology.
Long-slit spectroscopy of the tips of the bipolar lobes was secured to determine the gas ionization mechanism, physical conditions,
and line-of-sight velocities. An estimate of the proper motions at the tip of the south lobe using archival plate images is attempted.
The existing multi-wavelength data for Sh 2-129 and HR 8119 are also comprehensively reviewed.
Results. The observed morphology of Ou4, its emission-line spatial distribution, line flux ratios, and the kinematic modelling de-
veloped adopting a bow-shock parabolic geometry, illustrate the expansion of a shock-excited fast collimated outflow. The observed
radial velocities of Ou4 and its reddening are consistent with those of Sh 2-129 and HR 8119. The improved determination of the
distance to HR 8119 (composed of two B0 V and one B0.5 V stars) and Sh 2-129 is 712 pc. We identify in WISE images a 5 -radius
(1 pc at the distance above) bubble of emission at 22 µm emitted by hot (107 K) dust grains, located inside the central part of Ou4 and
corresponding to several [O iii] emission features of Ou4.
Conclusions. The apparent position of Ou4 and the properties studied in this work are consistent with the hypothesis that Ou4 is
located inside the Sh 2-129 H ii region, suggesting that it was launched some 90,000 yrs ago by HR 8119. The outflow total kinetic
energy is estimated to be ≈ 4 × 1047
ergs. However, the alternate possibility that Ou4 is a bipolar planetary nebula, or the result of an
eruptive event on a massive AGB or post–AGB star not yet identified, cannot be ruled out.
Key words. ISM: individual objects: Ou4 – ISM: jets and outflows – (ISM:) HII regions – (ISM:) planetary nebulae: general Stars:
winds, outflows – Stars: early-type
1. Introduction
The remarkable nebula Ou4 was discovered by the French am-
ateur astronomer Nicolas Outters while imaging the Sh 2-129
nebula in June 2011 by means of a 12.5 hour CCD exposure
with a F/5 106mm-diameter refractor (resulting in a plate scale
of 3.5 pix−1
) and a narrow (∼30 Å FWHM) [O iii] filter. It is a
clear example of the relevant science that can be done with very
small telescopes: the long integrations that can be obtained by
dedicated amateur astronomers allow very faint detection levels
to be reached, which are sometimes difficult to achieve with pro-
fessional telescopes given the limited amount of time available1
.
Ou4 was introduced and discussed by Acker et al. (2012). Its
highly bipolar morphology is mainly visible in the [O iii] 5007 Å
light. The total length of the nebula is 1◦.2 on the sky. The driving
Based on observations, obtained under Director’s Discretionary
Time of the Spanish Instituto de Astrofí sica de Canarias, with the
2.5m INT and the 4.2m WHT telescopes operated on the island of La
Palma by the Isaac Newton Group of Telescopes in the Spanish Obser-
vatorio of the Roque de Los Muchachos.
These authors equally contributed to this work.
1
Note that the detection limit per resolution element of an extended,
uniform source does not depend on the telescope size, but only on its
focal ratio.
source, the nature, and the distance of Ou4 are not known. Acker
et al. (2012) discussed several possibilities, including the one
that Ou4 is a very nearby planetary nebula (PN).
Motivated by the impressive size and remarkable morphol-
ogy of Ou4, we have obtained new optical images and spectra
with the aim to shed light on its origin. In Sect. 2, we describe
the relative position in the sky of Ou4 and the H ii region Sh 2-
129, and discuss the distance to the latter. Our imaging and spec-
troscopic observations are presented in Sect. 3. We analyse these
results in Sect. 4, and discuss the nature of Ou4 in Sect. 5.
2. Ou4 and the Sh 2-129 nebula
2.1. Multi-wavelength view of the Sh 2-129 nebula
A multi-wavelength view of the Sh 2-129 H ii region is pre-
sented in Fig. 1. The R-band DDS2 image mainly shows the
Hα line emission. This defines the boundary of this ionised re-
gion, which consists of a bright semicircle on the east side and
a fainter elongated bubble protruding towards the north-west di-
rection. This morphology is typical of an evolved H ii region in
the Champagne phase (Tenorio-Tagle 1979): the ionising flux of
a hot young star originally embedded near the edge of a molec-
ular cloud produced an expanding spherical H ii region which
Article number, page 1 of 13
3. A&A proofs: manuscript no. ou4_high_res
15m00s 10m00s 05m00s 21h00m00s
61d00m00s30m00s60d00m00s30m00s59d00m00s
Right Ascension (J2000)
Declination(J2000)
5 pc @ 712 pc
Fig. 1. The blister H ii region Sh2-129 and Ou4. The DSS2 R-band im-
age is shown in greyscale in the background. The red contour map is
the Green Bank 6 cm survey (Condon et al. 1994) using 10 contours
from 0.01 to 2.8 Jy/beam with a linear step. The green contour map is
a smoothed and thresholded [O iii] image. The image and contour map
scales are logarithmic. The white arrowed line has a length of 1◦.2 and
indicates the position of the giant outflow Ou4. HR 8119, the young
massive star ionising Sh 2-129, is close to the middle of this line.
pierced the cloud surface producing a flow of ionised gas (e.g.,
Yorke et al. 1983).
The Green Bank 6 cm survey (Condon et al. 1994; red con-
tour map in Fig. 1) shows the free-free continuum emission from
the border of this blister H ii region. In a large field-of-view
[O iii] image of Sh 2-1292
(green contour map) the [O iii] emis-
sion of Ou4 appears as superposed and centred on the fainter
emission from the hot gas that fills the semi-spherical H ii region
of Sh 2-129 and cools within the Champagne flow.
Infrared images obtained with the Wide-field Infrared Sur-
vey Explorer (WISE; Wright et al. 2010) unveil the dust emis-
sion in this area (Fig. 2). Bright dust pillars are present at the
eastern border of the bubble, but they are associated to a smaller
H ii region according to Anderson et al. (2014). This small H ii
region and dust pillars are typical of star-forming region. This
star-forming region may have been triggered by the expansion
of Sh 2-129. In the central part of Sh 2-129 a 5 -radius bubble
of emission at 22 µm shows up. Such an emission is usually ob-
served inside H ii regions where the central hot star heats dust
grains (e.g., Deharveng et al. 2010); for instance, the dust pillars
of the smaller H ii region are also surrounded by 22-µm emis-
sion. The morphology of the Sh 2-129 mid-infrared bubble and
its relation with Ou4 will be discussed in Sect. 4.5.
We used 2MASS (Skrutskie et al. 2006) to identify young
star candidates in the central part of Sh 2-129, in a radius of 30
2
The original image was obtained by another French amateur as-
tronomer, Stéphane Zoll, on August 2012 by means of a 7.3 hour
CCD-exposure with a F/3.6 106mm-diameter refractor (plate scale of
4 pix−1
) and a narrow (∼50 Å FWHM) [O iii] filter, and posted on
www.astrosurf.com . We used Aladin (Bonnarel et al. 2000) to register
it to the DSS2 image.
15m00s 21h10m00s
30m00s60d00m00s59d30m00s
Right Ascension (J2000)Declination(J2000)
5 pc @ 712 pc
G099.087+07.503
G098.490+07.891
Fig. 2. Mid-infrared image of Sh 2-129 obtained from the WISE All-
Sky Atlas. The blue, green, and red colours code to the WISE infrared
bands W2, W3, and W4 centred at 4.6, 12, and 22 µm-filters, respec-
tively. The green contour map is the same [O iii] image shown in Fig. 1.
The dashed white circles indicates the two (radio quiet) H ii regions in
the WISE catalog of Galactic H ii regions (Anderson et al. 2014). The
red diamonds mark the classical T Tauri star candidates that we have
identified inside the 30 -radius red circle centered on HR 8119 (see la-
bels in Fig. 3).
Fig. 3. Near-infrared colour-colour diagram of sources around
HR 8119. Grey asterisks are 2MASS sources with good photometry lo-
cated at a maximum angular distance of 30 from HR 8119 (see red cir-
cle in Fig. 2). Contours indicate the source density. The continuous and
dashed lines are the locii of main-sequence and giant stars of Bessell
& Brett (1988). The dotted-dashed line is the locus of the classical T
Tauri stars (Meyer et al. 1997). The arrows show the extinction vectors
(Cohen et al. 1981). The classical T Tauri star candidates are labelled.
from HR 8119. We selected only sources with good photome-
try (AAA flag) to build a colour-colour near-infrared diagram in
the 2MASS photometric system (Fig. 3). The comparison with
Article number, page 2 of 13
4. Romano L.M. Corradi et al.: Gas physical conditions and kinematic of the giant outflow Ou4
the locus of classical T Tauri stars (CTTSs) in this diagram3
.
allows us to identify four CTTS candidates by their infrared-
excess. There is no source with stronger infrared-excess in this
area, i.e., no protostars. These CTTS candidates are not located
in the vicinity of HR 8119, but close to the east border of our se-
lection area; one object has an optical extinction of about 7 mag,
whereas the other sources do not have an optical extinction larger
than 1 mag.
2.2. The distance to HR 8119 and Sh 2-129
Georgelin & Georgelin (1970) identified the hot (spectral type
B0 V, Hiltner 1956) star HR 8119 (a.k.a. HD 202214) as the ion-
ising source of Sh 2-129. Consequently, HR 8119 and Sh 2-129
must be located at the same distance. We also note that HR 8119
is the star with the earliest spectral type in the stellar group that
is visible at the centre of this blister H ii region according to
SIMBAD. This young star is a member of the Cepheus OB2 mas-
sive stars association (see, e.g., Fig. 3 of Patel et al. 1998)4
.
HR 8119 also lies in the central part of Ou4, as noted by Acker
et al. (2012).
Acker et al. (2012) estimated the distance of HR 8119
to be ∼870 pc by assuming no foreground extinction and an
absolute magnitude for main-sequence stars, but the distance
mostly used in the literature for Sh 2-129 is 400 pc. This latter
value is the spectrophotometric distance derived by Georgelin
& Georgelin (1970) assuming that HR 8119 is a single star.
However, HR 8119 is a triple system, where the separations ob-
tained from speckle interferometry between the primary and the
Ab and B components were 0.045 and 1.021, respectively, at
epoch 2005.8654 (Mason et al. 2009). We improve the distance
determination by combining the dynamical mass of HR 8119A
with evolutionary tracks of massive stars with solar metallicity
(Bertelli et al. 1994)5
. The orbital elements of the HR 8119Aa
and Ab components were published by Zirm & Rica (2012) and
flagged as reliable in the Sixth Catalog of Orbits of Visual Bi-
nary Stars6
. From the orbit semi-major axis (a = 0.066) and the
period (P = 56.93 yr), the following dynamical mass is obtained
for HR 8119A: Mdyn/M = 32.1×(P/56.93 yr)−2
×(a/0.066)3
×
(d/712 pc)3
, where d is the distance to HR 8119. The follow-
ing observational constraints are used: the spectral type B0 V
for the primary component, which corresponds to an effective
temperature of 31,500 K (Pecaut & Mamajek 2013); the differ-
ential V-band magnitude between the Ab and Aa components
(0.6 mag) in The Washington Visual Double Star Catalog (Ma-
son et al. 2001); and the Tycho-2 magnitudes of HR 8119A and
B, BT = 6.151 and 6.864 mag, and VT = 6.092 and 6.768 mag,
respectively (Høg et al. 2000), which are converted to B = 6.132
and 6.838 mag, and V = 6.085 and 6.757 mag, respectively,
using the filter transformations of Mamajek et al. (2002). Com-
parison of these photometric data with the evolutionary tracks
provides a best-fit age of 3.7 Myr, which gives a total mass of
32.0 M for HR 8119A7
, a distance of 712 pc, and a foreground
3
We use the colour transformations for the final 2MASS data release
at http://www.astro.caltech.edu/∼jmc/2mass/v3/transformations .
4
Note in particular that HR 8119 cannot belong to the Trumpler 37
stellar cluster which is located inside the IC 1396 H ii region (a.k.a.
Sh 2-131) at an angular distance of 4◦.3 east from Sh 2-129.
5
The CMD 2.5 web interface available at: http://stev.oapd.inaf.it/cgi-
bin/cmd was used.
6
Catalog available on-line at: http://www.usno.navy.mil/USNO/astro-
metry/optical-IR-prod/wds/orb6 .
7
For the Aa, Ab, and B components, respectively: the masses are 17.8,
14.2, and 16.7 M ; the effective temperatures are 31500, 29100, and
visual extinction of 1.1 mag. The latter is consistent with the
computed colour excess of HR 8119B (adopting RV = 3.1). The
age determination is consistent with the rather evolved evolu-
tionary status of this H ii region and the lack of 2MASS sources
(Skrutskie et al. 2006) with near-infrared excess (i.e., accretion
circumstellar disc) in the vicinity of HR 8119. Therefore, we
adopt a distance of 712 pc to HR 8119 and Sh 2-129.
3. Observations
3.1. Imaging of Ou4
The imaging was carried out on 18 August 2012 at the F/3.3
2.5m Isaac Newton Telescope (INT) at the Observatorio del
Roque de los Muchachos (ORM), La Palma, Spain. Images were
taken with the Wide Field Camera (WFC) in three filters: a
narrow-band [O iii] filter, with a central wavelength of 5008 Å
and a bandpass of 100 Å; a narrow-band Hα filter, with a central
wavelength of 6568 Å and a bandpass of 95 Å, thus including
the [N ii] doublet around Hα; and a broadband Sloan g filter,
with a central wavelength of 4846 Å and a bandpass of 1285 Å.
The plate scale is 0.33 pix−1
, and the seeing varied from 1.2
to 2.0 during of the night. As the field of view of the WFC is
34×34 arcmin2
, in order to cover the totality of Ou4 and the gaps
between CCDs in the detector mosaic, six different telescope off-
sets, with generous overlapping among them, were adopted: at
each of them, we exposed for a total of between 15 min and 45
min in [O iii], 5 and 15 min in Hα, and 90 sec in the g filter. The
night was dark: any significant moonlight would prevent detec-
tion of the nebula over the background given its very low surface
brightness (see Sect. 4).
Images were reduced using the INT+WFC pipeline in Cam-
bridge (CASU). Precise astrometric solution allowed a careful
combination of all images using the swarp software (Bertin et al.
2002). The final mosaic has a field of view of roughly 0◦.9 × 1◦.4.
As Ou4 and the surrounding H ii region Sh 2-129 cover the whole
field of view of the camera, accurate background subtraction
proved to be difficult and had to be carefully tuned. Figure 4
shows the colour-composite INT image of Ou4, while Fig. 5
shows the [O iii] and Hα+[N ii] images with labels on the most
relevant morphological features discussed below.
3.2. Spectroscopy of the lobe tips
Spectra of Ou4 were obtained on 17 August 2012 with the
4.2m WHT telescope and the double-arm ISIS spectrograph.
The long slit of ISIS was opened to 1 -width and positioned
in the southern tip of the nebula at P.A.=344◦
, crossing the
bright ridge of the nebula at coordinates R.A.=21h
13m
23s.8 and
Dec=+59◦
23 40.5 (J2000.0), as indicated in Fig. 6 by the long
blue slit.
In the blue arm of ISIS, grating R300B was used, provid-
ing a dispersion of 1.7 Å per (binned ×2) pixel, a resolution of
3.5 Å, and a spectral coverage from 3600 to 5200 Å. In the red
arm, grating R158R gave a dispersion of 1.84 Å pix−1
, a reso-
lution of 3.5 Å, and a spectral coverage from 5400 to 7800 Å.
Total exposure times was 2 hours. The spatial scale was 0.4 per
binned pixel in the blue, and 0.44 in the red. Seeing was 1.0.
30800 K (corresponding to B0 V, B0.5 V, and B0 V spectral types
according to Pecaut & Mamajek 2013; the luminosities are 41370,
20398, and 33595 L ; the intrinsic (B−V)0 colours are −0.279, −0.265,
and −0.275; the observed V-band magnitudes are 6.579, 7.179, and
6.757 mag.
Article number, page 3 of 13
5. A&A proofs: manuscript no. ou4_high_res
21h10m00s
30m00s60d00m00s59d30m00s
Right Ascension (J2000)
Declination(J2000)
5 pc @ 712 pc
Fig. 4. Colour composite mosaic image of Ou4 obtained with the Wide Field Camera of the 2.5m INT. The [O iii] 5007 emission is mapped in
green, Hα+[N ii] in red, and the broadband g filter in blue. Intensity scale is logarithmic. The field of view is 1◦.36×0◦.89. The vertical line indicates
the linear size if Ou4 is at the adopted distance of HR 8119 and Sh 2-129 (712 pc). North is up, east is left.
Article number, page 4 of 13
6. Romano L.M. Corradi et al.: Gas physical conditions and kinematic of the giant outflow Ou4
21h10m00s
30m00s60d00m00s59d30m00s
Right Ascension (J2000)
Declination(J2000)
5 pc @ 712 pc
21h10m00s
30m00s60d00m00s59d30m00s
Right Ascension (J2000)
Declination(J2000)
5 pc @ 712 pc
21h10m00s
30m00s60d00m00s59d30m00s
Right Ascension (J2000)
Declination(J2000)
5 pc @ 712 pc
Fig. 5. The [O iii] 5007 (left and middle) and Hα+[N ii] (right) mosaic images of Ou4. The sharpness of the [O iii] 5007 image was enhanced in the
middle panel using a blurred mask. The colour scale is logarithmic in the left and the right panel. The field of view in each panel is 1◦
.36 × 0◦
.89.
North is up, east is left.
The spectrophotometric standard BD+28 4211 from Oke (1990)
was observed during the night for flux calibration.
In order to determine the basic kinematic properties of the
outflow, spectra at a higher resolution were also obtained on 24
October and 25 December 2012 using the same instrument but
grating 1200B. Useful data are limited to the [O iii] 5007 Å line,
at which a spectral dispersion of 0.22 Å pix−1
and a resolution of
0.84 Å was achieved with the adopted 0.9 slit width. The slits,
also indicated in Fig. 6 in red, cross the south and north tips of the
lobes of Ou4 at positions 21h
13m
25s.2, +59◦
23 46.7 (J2000) at
P.A.=340◦
, and 21h
10m
21s.8, +60◦
29 10.6 at P.A.=20◦
, respec-
tively. Total exposure times were 40 min in the south lobe, and
80 min in the fainter north lobe.
Spectra were reduced with the standard procedure using the
longslit package of iraf V2.168
.
4. Analysis
4.1. Overall morphology of Ou4
The bipolar nebula is mainly visible in the [O iii] 5007
light (green colour in Fig. 4, and left and middle pan-
els of Fig. 5), whose surface brightness ranges from a
few 10−16
erg cm−2
s−1
arcsec−2
(tip of southern lobe, see
Sect. 4.3) down to the detection limit of our images of several
10−17
erg cm−2
s−1
arcsec−2
(in regions not contaminated by the
diffraction halo of bright stars).
As described in Acker et al. (2012), Ou4 is mainly composed
of two collimated lobes with arc-shaped tips of enhanced [O iii]
8
Iraf is distributed by the National Optical Astronomy Observatory,
which is operated by the Association of Universities for Research in As-
tronomy (AURA) under cooperative agreement with the National Sci-
ence Foundation.
emission. Their extremities recall the bow-shocks observed in
collimated stellar outflows such as Herbig-Haro objects in the
outflows from Young Stellar objects (Reipurth & Bally 2001),
or in high velocity bipolar PNe. The south lobe, of cylindrical
shape, is longer than the northern one, which instead has a more
conical overall morphology. Neither lobe can be easily followed
back to the central region, where a large distorted “bubble” is
visible. This prevents a safe association of the nebula with one
of the stars near its symmetry centre. Only the eastern ridge of
the south lobe extends back enough to provide some useful in-
dication. The lobe is wide till close to centre, where its edge is
bowl shaped and bends toward a direction approximately point-
ing to HR 8119 (Fig. 7). However, detection of the faint emission
from the lobe at distances smaller than ∼ 2.2 from HR 8119
are prevented by the bright diffraction halo of this star. This
marked lobe curvature near the centre is similar, for instance,
to that of the inner lobes of the bipolar PN Mz 3 (Santander-
García et al. 2004) or of several proto-PN such as Hen 401 (Sahai
et al. 1999; Balick et al. 2013). The overall morphology of Ou4
is very similar to that of the giant bipolar PN KjPn 8 (López et al.
1995), which has a size of 7.3 pc × 2.1 pc for the kinematically-
determined distance of 1.8±0.3 kpc (Boumis & Meaburn 2013).
Compared to the discovery image, the INT mosaic reveals a
wealth of new details. In addition to the above-mentioned cen-
tral bubble, another elliptical bubble breaks the inner regions of
the northern lobe. Also, in the central region of the south lobe
a “hole” is visible as well as “ripples” directed perpendicularly
to its long-axis. East of the central distorted bubble, additional
features in the form of “streamers” and “arcs” can be identified
(Fig. 5). Finally, the tips of the lobes, and in particular the south-
ern one, are composed of complex systems of multiple arcs (see
also Fig. 6). The main properties of Ou4 determined in this work
are summarised in Table 1.
Article number, page 5 of 13
7. A&A proofs: manuscript no. ou4_high_res
3arcmin(0.6pc)
Fig. 6. Details of the north (top) and south (bottom) bow-shocks in the
[O iii] light. The field of view in each panel is 10 × 4 . North is up, east
is left. The slit position for the lower resolution spectrum is indicated
by the long (blue) slit. The reference star 2MASS J21131972+5925365
adopted as the zero–point of the x–axis in Fig. 8 is visible at its north
end. The positions for the higher resolution spectra are indicated by the
short (red) slits.
3arcmin(0.6pc)
Fig. 7. The innermost region of the south lobe in the [O iii] light. The
field of view is 10 × 4 . North is up, east is left. Its eastern edge has a
marked curvature and approximately points toward HR 8119 (indicated
by the white circle).
In the Hα+[N ii] filter (red colour in Fig. 4, and right panel
of Fig. 5), emission is dominated by ambient gas belonging to
the H ii region Sh 2-129 with little contribution from Ou4 except
at specific regions like the south and north bow-shocks.
4.2. Emission line distribution in the tip of the south lobe
Insights into the excitation and dynamics of the nebula are
gained by looking at the spatial distribution of different ions.
This is shown in Fig. 8 for the lower resolution ISIS spectrum
cutting the tip of the southern lobe approximately south-north
(cf. bottom panel of Fig. 6). The upper panel of Fig. 8 shows the
spatial distribution of representative lines with the highest ioni-
sation potential, such as [O iii] 5007 and [Ne iii] 3869, while the
middle and bottom panels present those with lower ionisation
potential (Hα, [N ii], [S ii], and [O ii]). Profiles were smoothed
with a boxcar filter size of 3 spatial pixels (1.3). The field star
2MASS J21131972+5925365, visible at the upper end of the
long blue slit in the bottom panel of Fig. 6, was used to anchor
the blue and red spectra and define the zero–point of the spatial
scale. Negative distances refer to positions south of the reference
star.
Table 1. The main properties of Ou4.
Ou4
Lobe angular size 1◦.16 × 0◦.20
Linear size 14.4 pc × 2.5 pc (712 pc)
Centre∗
21h
11m
45.6 +59◦
59 00 Equ. J2000
HR 8119 21h
11m
48.2 +59◦
59 11.8 Equ. J2000
98◦.5202 +07◦.9852 Gal. J2000
Tip of the South lobe
Optical extinction 1.1±0.4 mag
Te([O iii], [O ii]) 55,000 K, ≥20,000 K See §4.3
Ne([S ii]) ≥50–100 cm−3
See §4.3
Proper motion 0.06±0.03 yr−1
tentative See §4.4.2
RV range†
−100 — +10 km s−1
Velocity 112 km s−1
See §4.4.3
Tip of the North lobe
RV range†
−55 — +40 km s−1
Velocity 83 km s−1
See §4.4.3
∗
Approximate symmetry centre of the Ou4 nebula.
†
Heliocentric, determined in the region covered by the slit (see
Fig. 9).
The sharp edge of the southern lobe corresponds to the peak
in the [O iii] 5007 emission at a distance d = −115 . [Ne iii] has
a similar behaviour, though the main peak is not equally pro-
nounced. Ahead of the [O iii] peak (i.e., at d < −115 ), signif-
icant Hα and [N ii], and to less extent [O ii] and [S ii] emission,
can be associated with the H ii region Sh 2-129. These lower ion-
isation ions also contribute to the emission of Ou4, as shown by
the several peaks at d > −115 , but their overall distribution is
obviously shifted to the north (i.e., “inside” the lobe) compared
to [O iii]. In particular, [O ii] 3727, which is at least as bright as
[O iii] 5007 (even taking into account mixing with the emission
of Sh 2-129), peaks about two arcseconds north of [O iii]. Some
faint [O i] 6300 emission, not shown in Fig. 8, is also detected
inside the lobe. No significant differences are seen in the profiles
of other lines not shown in Fig. 8, and in particular [O iii] 4363
is similar to [O iii] 5007, Hβ to Hα, and [S ii] 6731 to [S ii] 6716.
This overall distribution, with the higher ionisation ions out-
ward and the lower ionisation ones progressively inward, is a
first indication that the gas in the tip of the south lobe of Ou4
is shock-excited. Photoionisation from a central source would
instead produce an opposite stratification with the higher ionisa-
tion ions inwards.
4.3. Gas physical conditions from emission line ratios
Line fluxes for the Ou4 outflow were measured in the low-
resolution spectrum crossing the tip of south lobe. A precise
background subtraction is limited by the overlapping emission
of the H ii region Sh 2-129, which surface brightness is highly
variable at different spatial scales as it can be seen in the right
panel of Fig. 5 and in Fig. 4. We have done several tests, and
finally adopted a background (night sky + Sh 2-129) determined
using the portion of the spectrum of the northernmost part of
the slit, near the adopted reference star (Fig. 6). This is likely to
leave some small contamination by Sh 2-129. Note that, how-
ever, the main conclusions of the analysis presented below are
not affected by a different choice of the region used for back-
ground subtraction.
The ionisation stratification discussed in the previous section
makes the line ratios highly dependent on the selected spatial
Article number, page 6 of 13
8. Romano L.M. Corradi et al.: Gas physical conditions and kinematic of the giant outflow Ou4
Fig. 8. Spatial profile of selected emission lines through the tip of the southern lobe, along the slit shown in blue colour in Fig 6. Emission of
different ions has been scaled by the factors indicated in the labels. Regions corresponding to field stars are masked. The vertical dotted line show
the integration limits for the line flux measurements presented in Table 2.
region over which flux is integrated. We present in Table 2 line
fluxes measured in the shocked gas between −117 and −112
from the reference star in the south lobe, around the main peak
of the [O iii] emission. These integration limits are indicated by
the vertical dotted lines in Fig. 8, and do not include the cooling
region of lower excitation behind the shock.
In order to derive physical quantities from these fluxes, the
nebular extinction is required. The logarithmic extinction con-
stant cβ has been determined from the Balmer decrement by av-
eraging the results from the observed Hα/Hβ and Hγ/Hβ ratios
in our long-slit spectra. The theoretical Balmer line ratios were
adopted from Brocklehurst (1971) for electron temperatures be-
tween 10000 and 20000 K and a low density regime (Ne ∼ 102
,
see below). Rather than using only the narrow spatial region of
the shocked gas around the [O iii] peak, to determine an average
value of the extinction of the south lobe of Ou4 (which can be
patchy at these relatively large angular sizes) we have considered
a broader area between −117 and −105 from the reference
star, where most of the Balmer line emission in the region cov-
ered by our long slit is produced (see Fig. 8). This also includes
part of the cooling region behind the shock. We derive a value
of cβ=0.5±0.2 using the reddening law of Fitzpatrick (1999) and
RV=3.1. This corresponds to AV=1.1±0.4 mag. The same value,
within the errors, is found for the emission from Sh 2-129 ahead
of the shock. This cβ value was adopted to deredden the fluxes
in Table 2. This foreground extinction value is also similar to the
one that we found for HR 8119 in Sect. 2.
Physical conditions in the gas (electron density and temper-
ature) were then computed using the nebular package within
iraf, based on the five-level atom program originally published
by De Robertis et al. (1987), and further developed by Shaw &
Dufour (1995). From the [S ii] doublet, we obtain an electron
density Ne of between 50 cm−3
and 100 cm−3
depending on the
adopted temperature. This is a lower limit for the gas density in
the tip of the south lobe of Ou4, as the [S ii] emission mainly
comes from the inside boundary of the selected region of the
spectrum (see Fig. 8) and therefore traces a different nebular
zone than [O iii]. In addition, non-negligible residual contribu-
tion of [S ii] emission from the overlapping low-density Sh 2-
129 could be present. The electron temperature Te derived from
the [O iii](5007+4959)/4363 line ratio is as large as 55,000 K for
this density. This is a very high Te, which could be reduced to
values typical of photoionised nebulae only if Ne had the value
of 107
cm−3
in the O2+
emitting region. On the other hand, [O ii]
Article number, page 7 of 13
9. A&A proofs: manuscript no. ou4_high_res
Table 2. Observed and dereddened (adopting cβ=0.5) line fluxes in the
shock region between -112 and -117 (see Fig. 8) of the south lobe.
Fluxes are normalised to Hβ=100. The observed Hβ integrated flux in
the area is 4.03 10−16
erg cm−2
s−1
. The derived physical quantities are
Ne([S ii])=50–100 cm−3
and Te([O iii])=55,000 K.
Line identification Flux
Observed Dereddened
[O ii] 3726+3729 883.1 1262.3
[Ne iii] 3869 72.5 99.3
[Ne iii] 3968+H 35.9 47.7
Hδ 4101 18.9 24.1
Hγ 4340 45.7 53.8
[O iii] 4363 55.4 64.7
Hβ 4861 100.0 100.0
[O iii] 4959 237.8 231.1
[O iii] 5007 717.5 687.5
[N ii] 6548 94.3 63.1
Hα 6563 503.7 336.1
[N ii] 6583 308.3 205.0
[S ii] 6716 114.4 74.2
[S ii] 6731 87.0 56.3
[O ii] 7319 51.8 30.6
[O ii] 7330 53.7 31.7
is expected to be produced in the same region as [S ii] (but note
the additional emission peak of [O ii]7330 in Fig. 8), and there-
fore the [S ii] density can be adopted to compute Te from the
[O ii](3726+3729)/(7320+7330) line ratio. The latter ratio also
suggests a high electron temperatures (≥20,000 K), even though
at low densities the [O ii] indicator runs into its asymptotic value.
Such a Te, too high to be produced by photoionisa-
tion, is another proof that the gas at the tip of the lobes
of Ou4 is ionised by shocks. This conclusion is further
supported by standard shock excitation diagnostic line ra-
tios. In this nebular region, log(Hα/[N ii]6548+6583)=0.1 and
log(Hα/[S ii]6716+6731)=0.4, which locates Ou4 together with
shock-excited sources such as Herbig–Haro objects (see e.g. Vi-
ironen et al. 2009). The same conclusion is reached by analysing
other portions of the slit. The lower-excitation emission inside
the lobes is therefore expected to be the recombining/cooling re-
gion behind the shock. Integrating the [N ii](6548+6583)/5755
between slit positions -117 and -105 , including the main
[N ii] emission peak, we consistently obtain a lower temperature,
Te∼14,400 K.
The electron density of gas in the relatively bright region of
Sh 2-129 ahead of the bow-shock (from -150 to -130 from
reference star), determined from the [S ii]6716,6731 doublet, is
Ne=55 cm−3
assuming a typical Te for H ii regions of 10,000 K.
Because this emission region is located on the ionized boundary
of the H ii region, this electronic density is the one of the molec-
ular cloud.
To estimate the electronic density inside the H ii region we
use the Hα emission measure along the line-of-sight, EM =
H ii
N2
e ds, which can be computed from the Hα surface bright-
ness corrected from extinction, I, with the following formula:
EM/(1 cm−6
pc) = 2.75 × (T/10, 000 K)0.9
× (I/1 R), which is
valid for temperature between 5,000 and 10,000 K, and where R
is one Rayleigh, i.e., 2.42 × 10−7
ergs cm−2
s−1
sr−1
at the Hα
wavelength (Reynolds 1977). We assume for the H ii region a
typical temperature of 10,000 K. From the Virginia Tech Spec-
tral line Survey (VTSS; Finkbeiner 2003), which mapped the
north-west half-part of Sh 2-129 in Hα with 6 (FWHM) reso-
lution, we obtain the radial profile from HR 8119 for a position
angle of ≈26◦
of the Hα intensity in R unit, and deredden it us-
ing AV=1.1 mag and the extinction law of Fitzpatrick (1999).
This intensity is modeled with a uniform intensity of 22.3 R
plus a constant-density (hemi-)spherical shell geometry to repro-
duce the limb brightening (e.g., Nazé et al. 2002), and convolved
with a 6 -FWHM Gaussian. To reproduce the external profile we
need a shell-radius of 0◦.76 (i.e., 9.4 pc at a distance of 712 pc),
a shell-thickness of 0◦.14, and a shell-density of 5.1 cm−3
. The
constant-density inside the shell is estimated to about 1.7 cm−3
.
This lower electronic density of the blister H ii region compared
to the molecular cloud is the result of the ionization and heat-
ing by the central early-type B stars, which have produced the
Champagne flow.
If Ou4 is embedded in Sh 2-129, the pre-shock gas density is
the electronic density inside this H ii region. Since this shock is
radiative, the gas behind the shock relaxes to the H ii region tem-
perature and if there is no magnetic field the shock compression
ratio scales as Mach-number squared (Draine & McKee 1993).
Taking γ = 5/3 for the ratio of specific heat and µ = 0.7 for
the mean molecular weight inside the H ii region, the sound ve-
locity is 14 km s−1
and a shock velocity of 112 km s−1
(see be-
low Sect. 4.4.3) gives a Mach number of 8.0, which leads to a
compression ratio of 64. Therefore, the post-shock gas density is
estimated to 110 cm−3
.
4.4. Kinematics of the lobe tips
4.4.1. Radial velocities
Heliocentric line-of-sight velocities in regions at the tip of each
lobe were computed from the Doppler shift of the [O iii] 5007
line in the higher resolution spectra described in Sect. 3.2. The
slit locations are indicated in Fig. 6. Wherever possible, two
Gaussians were fitted to the spectra at different slit positions,
binning the information every 4 arcseconds to increase the S/N.
The resulting position velocity plot is presented in Fig. 9. Ac-
curacy in the double-Gaussian fitting is mainly limited by the
separation and shape of the profiles of the two line components.
At the positions where they cannot be resolved, only a single
Gaussian could be measured with generally large FWHM result-
ing by the blending of the two components. For this reason, we
indicate in Fig. 9 the FWHM of the Gaussian line fits rather than
the (smaller) formal error of the fitting.
The plot shows that there is only a small overall velocity dif-
ference between the two bow-shocks, indicating that the outflow
is likely to be oriented near the plane of the sky. The north lobe
would recede from us, and the south one approach us. Right in-
side each lobe, the [O iii] emission can be split into two compo-
nents which are separated by up to about 100 km s−1
in the small
fraction of the lobe length covered by these observations. There-
fore a lower limit for the lobe “transverse” velocity can be set to
50 km s−1
.
In Fig. 9, the radial velocities of HR 8119 and Sh 2-129
are also shown. The former (−16.2 km s−1
, blue dotted line)
is from Wilson (1953). The Hα average velocity of Sh 2-129
(−23.5 ± 5.3 km s−1
) obtained using Perot-Fabry measurements
by Georgelin & Georgelin (1970) is indicated by the dashed
red line, while the dashed-dotted magenta line represents the
CO peak located east of HR 8119 on the border of Sh 2-129
(−28.5 ± 0.7 km s−1
; Blitz et al. 1982). The velocity of the two
lobes is symmetrically located with respect to the massive star
Article number, page 8 of 13
10. Romano L.M. Corradi et al.: Gas physical conditions and kinematic of the giant outflow Ou4
Fig. 9. Position-velocity plot at the tips of the lobes. Position zero is de-
fined at the point at which the slit crosses the end of each lobe. Positive
and negative positions indicate distances from this reference point along
the slits and toward the centre of the nebulae in the south and north lobe,
respectively. “Errorbars” indicate the [O iii] full-width-at-half maxi-
mum after correcting for the instrumental broadening. Solid lines show
our bow-shock kinematic model (see Sect. 4.4.3). The horizontal blue
dotted line indicate the heliocentric radial velocity of HR 8119, and the
dashed and dashed-dotted lines that of Sh 2-129 (see Sect. 4.4.1).
and the H ii region, further supporting their possible association
with Ou4.
4.4.2. Proper motions
We identify the tip of the south lobe in two B-band digitised
plates obtained at two different epochs separated by nearly
41 years (Fig. 10). We use the imwcs software9
and the
SExtractor software (Bertin & Arnouts 1996) to register these
B-band POSS1 and POSS2 images of Ou4 and our [O iii] INT
image to the 2MASS reference frame (Skrutskie et al. 2006).
However, the modest spatial resolution and the weak S/N ra-
tio prevent us to safely track any emission features between the
POSS1 and POSS2 epochs. Our tentative pairing of a few emis-
sion features leads to a proper motion upper-limit of ∼0.06 ±
0.03 yr−1
(or a tangential velocity of ∼ 200 ± 100 km s−1
if Ou4
is located at the distance of HR 8119), where the proper motion
error includes the error of the image registration and the deter-
mination of the features position.
4.4.3. Bow-shock kinematic model
The edges of the brightest working-surfaces of the south- and
north-lobe tips (Fig. 6) can be fitted with a parabola. Assum-
ing axisymmetry (see Fig. 1 of Hartigan et al. 1987), we can
then argue that the intrinsic shape of the working surface is a
paraboloid, as the projection onto the plane of the sky of such
a geometric figure for any inclination angle is a parabola (see
appendix of Hartigan et al. 1990). The actual 3D shape can then
be computed for a given inclination of the bow shock along the
line-of-sight.
In the shock rest frame, the parallel component of the ve-
locity of the incoming gas does not change through the working
surface, whereas the perpendicular component of the velocity is
strongly decreased (by a factor of 4 by the shock and about 10
9
The imwcs software is available at: http://tdc-www.harvard.edu/-
wcstools/imwcs .
30s 25s 21h13m20s 15s 10s
30s59d24m00s23m30s
Right Ascension (J2000)
Declination(J2000)
30s 25s 21h13m20s 15s 10s30s59d24m00s23m30s
Right Ascension (J2000)
Declination(J2000)
0.05 pc @ 712 pc
30s 25s 21h13m20s 15s 10s
30s59d24m00s23m30s
Right Ascension (J2000)
Declination(J2000)
Fig. 10. Proper motions of the tip of the south lobe of Ou4. Top and
middle panels: POSS1 (epoch 1952-07-22) and POSS2 (epoch 1993-
06-25) blue plates in logarithmic greyscale smoothed with a Gaussian
kernel (σ = 1.5) with green and blue contours overlaid, respectively.
Bottom panel: the green and blue contours overlaid on our [O iii] INT
mosaic (epoch 2012-08-19). The possible motions of four emission fea-
tures between the POSS1 and POSS2 epochs are indicated in each panel
by small red lines (average size of ∼ 2.5 ± 1.1).
by cooling; see Hartigan et al. 1987). Therefore, in the observer
frame the velocity of the emitting post-shock material, which
fills a rather thin shell behind the working surface, is nearly per-
pendicular to the paraboloid surface, its intensity is maximum
at the paraboloid vertex (i.e., equal to the shock velocity) and
decreases from this position. The observed bow-shock size is
directly controlled by the threshold value of the perpendicular
component of the velocity that is required to produce the line
emission conditions. For high inclinations the radial velocities
derived by long-slit spectroscopy have a characteristic "hook"
shape in a velocity-position diagram, where the observed range
of radial velocities is of the order of the actual bow-shock veloc-
ity (see Fig. 6 of Hartigan et al. 1990).
We build a toy model of this paraboloid bow-shock with the
shape and the size measured from our images where we can vary
the systemic radial velocity, the bow-show velocity and inclina-
tion along the line of sight, and compute the resulting radial ve-
locities of the emitting post-shock material along our long-slit
Article number, page 9 of 13
11. A&A proofs: manuscript no. ou4_high_res
positions. The systemic radial velocity is estimated by averaging
the first four (unresolved) radial velocity measurements at the
bow-shock heads, and is fixed to this value (−16.2 km s−1
) in
our simulations. We also assume the same minimum perpendic-
ular component of the velocity of the incoming gas in the shock
rest-frame. These simulated velocity-position diagrams are then
compared with the observed gas kinematic.
We show in Fig. 9 our best match for the south and north
bow-shocks which is obtained for an inclination of 60◦
and 100◦
(where 0◦
is a bow-shock directed towards us), and a shock ve-
locity of 112 and 83 km s−1
, respectively. The lower velocity of
the north bow-shock may explain why it is fainter than the south
one. This toy models allows us to reproduce the global properties
of the observed gas kinematic.
With these shock velocities the minimum value of the per-
pendicular component of the velocity of the incoming gas in the
shock rest-frame is 55 km s−1
. The minimum perpendicular ve-
locity needed to observe [O iii] is usually supposed to be equal
to 90–100 km s−1
, based on plane-parallel simulation of shock
emission (e.g., Hartigan et al. 1987). However, if Ou4 is located
inside the Sh 2-129 H ii region the pre-shocked gas already con-
tains O+2
(see Fig. 1), and the perpendicular velocity needed to
produce bright [O iii] may be lower. Confirming this hypothesis
would require detailed emission modelling of the bow-shock and
the H ii region which is well beyond the scope of this article.
These south and north bow-shock velocities correspond to
proper motions of 0.028× and 0.024 × (d/712 pc)−1
yr−1
,
respectively, and to kinematical time scales of 88, 300× and
87, 800 × (d/712 pc) yr, respectively. The poorly constrained
proper motion of the south bow shock obtained in the previous
section prevent us to derive a secure kinematic distance to Ou4.
However, we can likely exclude any distance lower than about
133 pc which should lead to an apparent expansion of the lobe
tips larger than our proper motion estimate plus 3 times our un-
certainty.
4.5. The central part of Ou4: [O iii] emission vs. mid-infrared
bubble
4.5.1. Morphology of the mid-infrared bubble
Figure 11 shows a contour map of the mid-infrared bubble de-
tected in the WISE W4-filter image in the central region of Ou4
overlaid on the [O iii] image. The angular resolution of the W4-
filter image is 12 (FWHM). The central point-like source is the
mid-infrared counterpart of HR 8119. The 5 -radius extended
emission is asymmetric, with a surface brightness which is on
average about 3 times higher on the eastern-side than on the
western-side. There are two peaks of emission, located at 1.8 -
east and 2.7 -north from HR 8119. The north and south exten-
sions of the mid-infrared bubble match the limit of the [O iii]
bubbles (see also the middle-left panel of Fig. 13 for the full
range of the W4 intensity). A weak extension of the infrared bub-
ble towards the East of HR 8119 corresponds to the base of the
[O iii] streamers. A ridge of mid-infrared emission is located on
the south-west border of the mid-infrared bubble. Fig. 12 is an
enlargement of this region. The mid-infrared counterpart of the
star HD 239597 (K2 spectral type in the Henry Draper catalogue
and extension) is barely resolved from the ridge emission. This
ridge emission corresponds to the [O iii] filaments that defines
the southern-limit of the Ou4 bubble.
13m00s 30s 21h12m00s 30s 11m00s 10m30s
03m00s60d00m00s57m00s59d54m00s
Right Ascension (J2000)
Declination(J2000)
1 pc @ 712 pc
Fig. 11. [O iii] emission from the central part of Ou4 vs. 22 µm emission.
The color scale of the [O iii] image is logarithmic. The contour map is
the 22 µm emission of the W4-filter image from 89.375 to 92.5 dig-
ital numbers (DN) with linear step of 0.446 DN (i.e., from 2.471 to
2.557 mJy/arcsec2
with linear step of 0.012 mJy/arcsec2
). The linear
scale is shown in the bottom-right corner.
30s 25s 21h11m20s 15s 10s 05s
30s59d56m00s30s55m00s
Right Ascension (J2000)
Declination(J2000)
W4
0.1 pc @ 712 pc
Fig. 12. Details of the [O iii] emission of Ou4 near the ridge of mid-
infrared emission. The bright star is HD 239597. The color scale of the
[O iii] image is linear. The contour map is the 22 µm emission from the
W4-filter image from 89.375 to 92.5 digital numbers (DN) with linear
step of 0.223 DN (i.e., from 2.471 to 2.557 mJy/arcsec2
with linear step
of 0.006 mJy/arcsec2
). The linear scale and the angular resolution of the
W4-filter image (12 -FWHM) are shown in the bottom-right corner.
4.5.2. Spectral energy distribution of the mid-infrared bubble
The location of the mid-infrared bubble inside the [O iii] emis-
sion may suggest line emission from hotter oxygen gas (e.g.,
[O iv] at λ = 25.87 µm) rather than continuum emission from
dust grains. Therefore to constrain the nature of the mid-infrared
bubble we build a spectral energy distribution (SED) of the
brightest emission peak by combining WISE (λeff =11.56 and
22.09 µm) and IRAS (λeff =10.15, 21.73, 51.99, and 95.30 µm)
photometry. We use the WISE All-Sky Atlas images (Cutri et al.
2012) and the Improved Reprocessing of the IRAS Survey (IRIS;
Miville-Deschênes & Lagache 2005) which provide us an angu-
lar resolution of 6.5, 12 , 3.8 , 3.8 , 4.0 , and 4.3 (FWHM) at
12, 22, 12, 25, 60, and 100 µm, respectively.
Despite the lower angular resolution of IRAS, the east-side
of the mid-infrared bubble is detected in the IRIS 25-µm image
(see the middle-right panel of Fig. 13). We use a custom IDL pro-
gram to perform circular-aperture photometry using a procedure
adapted from DAOPHOT. In all images, the source+background
area is centred on (21h
12m
02 , +59◦
58 58 ; J2000) with a ra-
Article number, page 10 of 13
12. Romano L.M. Corradi et al.: Gas physical conditions and kinematic of the giant outflow Ou4
312 321 330 338 347 356 365 374 382 391 400
13m00s 30s 21h12m00s 30s 11m00s 10m30s
05m00s60d00m00s55m00s59d50m00s
Right Ascension (J2000)
Declination(J2000)
a)
W3 beam
Intensity (DN)
background
source+background
87.8 88.3 88.8 89.3 89.9 90.4 90.9 91.4 92 92.5 93
13m00s 30s 21h12m00s 30s 11m00s 10m30s
05m00s60d00m00s55m00s59d50m00s
Right Ascension (J2000)
Declination(J2000)
W4 beam
b)
Intensity (DN)
background
1.2 1.7 2.2 2.7 3.2 3.7 4.2 4.7 5.2 5.7 6.2
13m00s 30s 21h12m00s 30s 11m00s 10m30s
05m00s60d00m00s55m00s59d50m00s
Right Ascension (J2000)
Declination(J2000)
c)
IRIS12 beam
Intensity (MJy/sr)
background
source+background
3.2 3.5 3.9 4.2 4.5 4.9 5.2 5.5 5.9 6.2 6.5
13m00s 30s 21h12m00s 30s 11m00s 10m30s
05m00s60d00m00s55m00s59d50m00s
Right Ascension (J2000)
Declination(J2000)
d)
IRIS25 beam
Intensity (MJy/sr)
background
source+background
10.3 11.2 12.1 13.1 14 14.9 15.8 16.7 17.7 18.6 19.5
13m00s 30s 21h12m00s 30s 11m00s 10m30s
05m00s60d00m00s55m00s59d50m00s
Right Ascension (J2000)
Declination(J2000)
e)
IRIS60 beam
Intensity (MJy/sr)
background
source+background
37 39 40 41 43 44 45 47 48 49 51
13m00s 30s 21h12m00s 30s 11m00s 10m30s
05m00s60d00m00s55m00s59d50m00s
Right Ascension (J2000)
Declination(J2000)
f)
IRIS100 beam
Intensity (MJy/sr)
background
source+background
19 43 66 90 113 137 161 184 208 231 255
13m00s 30s 21h12m00s 30s 11m00s 10m30s
05m00s60d00m00s55m00s59d50m00s
Right Ascension (J2000)
Declination(J2000)
g)
W4 beam
background
source+background
Fig. 13. Mid- to far-infrared views of the central part of Ou4. a) WISE
12-µm (W3-filter) image. b) WISE 22-µm (W4-filter) image. c) IRIS
12-µm image. d) IRIS 25-µm image. e) IRIS 60-µm image. f) IRIS 100-
µm image. g) INT [O iii] image for comparison purpose. The contour
map is the 22 µm emission from 89.375 to 92.5 digital numbers (DN)
with linear step of 0.446 DN (i.e., from 2.471 to 2.557 mJy/arcsec2
with
linear step of 0.012 mJy/arcsec2
). The FWHM resolution is plot in the
bottom-right corner of each panel. The two large circles are the regions
used for the aperture photometry (see text and Fig. 14).
dius of 2 to match the angular resolution of IRIS images, and
the background area is centred on (21h
12m
12.0, +59◦
50 24
; J2000) with a radius of 2.6 (Fig. 13). We subtract from the
extended-source fluxes in the W3, W4, IRAS12, and IRASS25
bands the resolved fluxes of HR 8119 in the WISE All-Sky cat-
alog (Cutri et al. 2012).
The resulting SED (Figure 14) shows significant flux emis-
sion in all bands, which is consistent with continuum emis-
sion from dust grains. Assuming that all grains have the same
size distribution and composition, the dust emission is a single-
Fig. 14. Spectral energy distribution of the infrared emission in the cen-
tral part of Ou4. Diamonds and triangles are IRIS and WISE data points,
respectively, obtained from aperture photometry (Fig. 13). Grey lines
show the transmission profiles of the IRAS and WISE broad-band fil-
ters, with vertical dotted lines indicating the effective wavelength. The
solid line is the dust emission (single-temperature modified black-body
model) fitted to the IRIS data points (diamonds) and asterisks are the
corresponding modeled fluxes in each filter. The dashed line is the cor-
responding black-body model.
temperature modified black-body emission, i.e., a black-body
emission multiplied by the dust emissivity (e.g., Draine 2004):
Fν = Ω × Bν(Tdust) × [1 − exp{−τdust(ν)}] where Ω is a solid an-
gle, Bν(Tdust) is the black-body of temperature Tdust, and τdust(ν)
is the optical depth. The dust optical depth along the line of sight
is defined by: τdust(ν) = κdust(ν) ρ ds, where κdust(ν) is the dust
opacity, and ρ is the dust mass-density. We use the dust opacity
corresponding to the Milky Way dust with RV = 3.1, computed
for the carbonaceous/silicate dust model (Weingartner & Draine
2001; Draine 2003). The low foreground-extinction can be ne-
glected. We convolve Fν with the transmission profiles of the
broad-band filters10
. We fit only the IRIS data points to mitigate
the variation of angular resolution with wavelength. Our best
fit11
is obtained for a dust temperature of 107 K. The decrease
of dust emissivity with wavelength affects only the fluxes in the
IRAS 60 and IRAS 100 bands (see dashed line in Figure 14). The
excess of emission in the IRAS 12 and W3 bands may be due
to additional emission from the background cloud. The excess
of emission observed in the W4 band compared to the model
prediction is likely due to the better angular resolution of WISE
compared to IRIS. Our model predicts a maximum of dust emis-
sion around 34 µm.
In conclusion, the overall SED is typical of continuum emis-
sion from hot dust grains.
5. Discussion and conclusions
Summarising, one of the main results of this study is that the
tip of the south lobe of Ou4 is shock ionised. This is clearly
indicated by the spatial distribution of the atomic emission, with
the higher ionisation species outwards and the lower excitation,
cooling post-shock gas inward, as well as by the observed line
ratios and gas physical conditions.
10
We use the Filter Profile Service of the Virtual Observatory available
at http://svo2.cab.inta-csic.es/svo/theory/fps3/ .
11
The two other physical parameters are: the diameter of the black-
body region (≡ 2d
√
Ω/π) of 89 AU for a distance, d, of 712 pc; and the
dust surfacic mass (≡ ρ ds) of 0.054 g cm−2
.
Article number, page 11 of 13
13. A&A proofs: manuscript no. ou4_high_res
The fact that this region is ionised by collisions rather than
by photons, does not require that the central source at the origin
of the outflow has the high temperature which would be needed
to excite, e.g., O2+
. Removing this constraint on the temperature
of the central source may weaken the hypothesis that Ou4 is a
PN. However, we do not have information about the ionisation
mechanism of the inner regions of Ou4. It may well be that, in
addition to shocks in the outermost regions outflow, a small pho-
toioinised core is present, such as in the case of the PN KjPn 8
(López et al. 1995).
We estimate the probability of an apparent association be-
tween H ii regions and PNe by cross-correlating the WISE cata-
logue of H ii region (Anderson et al. 2014), which provides H ii
angular radii from 6 to 1◦.6, with the catalogue of Galactic PNe
of Kohoutek (2001). We identify 29 on 1510 PNe (i.e., 1.6%)
that are located inside H ii regions in projection. The mean and
standard deviation of their Galactic latitudes is −0◦.2 and 1◦.5, re-
spectively, with a maximum angular distance from the Galactic
plane of 3◦.9. Therefore, lucky association of H ii regions and
PNe only occurs close to the Galactic plane due to the high
spatial-density of both kind of objects in this region of the sky.
Since the Galactic latitude of Sh 2-129 is high (b ≈ 8◦
), a fortu-
itous alignment with a PN appears as unlikely.
Given the apparent location of Ou4 in the sky, aligned with
the young stellar cluster at the centre of the H ii region Sh 2-129
and the striking correspondence between the 22 µm and [O iii]
emission, it is reasonable to suppose that Ou4 is an outflow
launched some 90,000 yr ago from the massive triple system
HR 8119. The location of the outflow, its radial velocities and
extinction values are all consistent with such an hypothesis. Fur-
ther support might come from the fact that the south bow-shock
has an enhanced brightness in correspondence with a bright por-
tion of Sh 2-129, as expected if it were impinging on a denser
zone at the border of the H ii region.
For comparison purpose, we estimate the kinetic energy of
the Ou4 outflow. With lobe size of 2.5 pc × 14.4 pc in ex-
tent, for a mean H ii density of 1.7 cm−3
and µ = 0.7, the dis-
placed mass is Mdisp ≈ 2.1 M . With a shock propagating at
≈100 km s−1
the kinetic energy of the outflow is K(outflow) ≈
4 × 1047
ergs, i.e., much lower than SNe. If the bipolar-cavity
was created by an episodic, collimated, bipolar jet/wind propa-
gating at 2,500 km s−1
(e.g., Steffen & López 1998), the conser-
vation of the kinetic-energy would imply a mass ejected by the
driving source of about Mejec ≈ 0.003 M . With a dynamical-
time of 88,000 yr, the required mass-loss rate would be there-
fore 3.8 × 10−8
M yr−1
. This value can be compared with the
mass-loss rate from the radiatively-driven winds of the central
massive stars. From the physical parameters of the stellar com-
ponents Aa, Ab, and B of HR 8119 in Sect. 2.2 we estimate
using the theoretical recipe of Vink et al. (2000) the mass-loss
rates of ≈ 2.5 × 10−8
, ≈ 0.6 × 10−8
, and ≈ 1.6 × 10−8
M yr−1
with terminal velocities of 2515, 2508, and 2517 km s−1
, respec-
tively. Therefore, the two-most massive stars of HR 8119 with
combined mass-loss rate of 4.1 × 10−8
M yr−1
and high ter-
minal velocity can easily provide the required kinetic energy to
drive Ou4. The larger separation of component Aa and B may
explain the episodic phenomenon, whereas the close Ab com-
panion could play a role in the outflow collimation.
In the alternative scenario that Ou4 is a PN, its overall mor-
phology would likely be the result of the expansion of a fast
collimated wind from a yet unidentified central source through
a relatively dense circumstellar medium. If the cooling time of
the shocked material (fast wind and/or ambient medium) is long
enough, the fast collimated wind can inflate the observed thin
lobes. The morphology of these lobes depends on several fac-
tors, mainly the opening angle of the fast outflow (Soker 2004).
In addition, as discussed by Sahai et al. (1999) for the pre-PN
Hen 401, the ambient density should decrease significantly with
distance from the source in order to produce the cylindrical neb-
ular morphology of the southern lobe. The presence of bow-
shocks and the “bowl” shape of the base of the southern lobe
star are also consistent with models considering the inflation of
bipolar lobes by fast collimated outflows seen nearly edge-on
(Soker 2002; Balick et al. 2013).
The study of this kind of collimated outflows in PNe and
related objects often suggests an eruptive nature of the phe-
nomenon, and that the central source is a binary system. The
possibility that the outflow of Ou4 is produced in an outburst
powered by mass accretion in a binary system, leading to a
phenomenon such as an intermediate-luminosity optical tran-
sient (ILOT) as proposed for e.g. KjPn 8 (Boumis & Meaburn
2013), other bipolar PNe (Soker & Kashi 2012), or for massive
(MZAMS ∼6–10 M ) carbon-rich AGB, super-AGB, or post-AGB
stars (Prieto et al. 2009), is an appealing one.
Concluding, it is clear that the stellar source at the origin of
the Ou4 outflow should be better constrained. A crucial infor-
mation in this respect is its distance. In the future, we aim at a
precise measurement of the proper motions of the outflow which,
combined with the line-of-sight velocities and kinematical mod-
elling, would provide a sound distance determination. A more
sensitive imaging of the vicinity of the bright star HR 8119 with
narrower filters centred on emission lines would be also valuable
to detect the origin of the outflow. In addition, extension of this
study to other wavelength domains is planned to better constraint
the nature of this unique giant outflow.
Acknowledgements. We thank the referee John Bally and the editor Malcolm
Walmsley for many useful suggestions that helped to improve our manuscript.
We are grateful to the time allocation committee (CAT) for awarding us IAC Di-
rector Discretionary Time at the WHT and INT. The higher resolution spectra
was secured during ING service time. We thank the ING staff, and in partic-
ular Javier Mendez, Raine Karjalainen, and the ING students for imaging at-
tempted on an additional night, which could not be used due to the strong moon-
light which prevented detection of the faint nebula. RLMC acknowledges fund-
ing from the Spanish AYA2007-66804 and AYA2012-35330 grants. We thank
Stéphane Zoll for his [O iii] image of Ou4. Finally, we are very grateful to Gabriel
Perez at the IAC for the careful edition of the colour image in Fig. 4. This re-
search has made use of Aladin, and of the SIMBAD database, operated at CDS,
Strasbourg, France. This publication makes use of data products from the Wide-
field Infrared Survey Explorer, which is a joint project of the University of Cal-
ifornia, Los Angeles, and the Jet Propulsion Laboratory/California Institute of
Technology, funded by the National Aeronautics and Space Administration.
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