- ID:
- ivo://CDS.VizieR/J/A+A/405/999
- Title:
- Unidentified infrared bands (UIR)
- Short Name:
- J/A+A/405/999
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a set of 6-12{mu}m ISOPHOT-S spectra of the general interstellar medium of the Milky Way. This part of the spectrum is dominated by a series of strong, wide emission features commonly called the Unidentified Infrared Bands (UIR). The sampled area covers the inner Milky Way from l=-60{deg} to +60{deg} with a ten-degree step in longitude and nominal latitudes b=0{deg}, +/-1{deg}. For each grid position the actual observed direction was selected from IRAS 100{mu}m maps to minimize contamination by point sources and molecular clouds.
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- ID:
- ivo://CDS.VizieR/J/ApJ/856/85
- Title:
- Unlocking CO depletion in protoplanetary disks. I.
- Short Name:
- J/ApJ/856/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CO is commonly used as a tracer of the total gas mass in both the interstellar medium and in protoplanetary disks. Recently, there has been much debate about the utility of CO as a mass tracer in disks. Observations of CO in protoplanetary disks reveal a range of CO abundances, with measurements of low CO to dust mass ratios in numerous systems. One possibility is that carbon is removed from CO via chemistry. However, the full range of physical conditions conducive to this chemical reprocessing is not well understood. We perform a systematic survey of the time dependent chemistry in protoplanetary disks for 198 models with a range of physical conditions. We vary dust grain size distribution, temperature, comic-ray and X-ray ionization rates, disk mass, and initial water abundance, detailing what physical conditions are necessary to activate the various CO depletion mechanisms in the warm molecular layer. We focus our analysis on the warm molecular layer in two regions: the outer disk (100au) well outside the CO snowline and the inner disk (19au) just inside the midplane CO snowline. After 1Myr, we find that the majority of models have a CO abundance relative to H_2_ less than 10^-4^ in the outer disk, while an abundance less than 10^-5^ requires the presence of cosmic-rays. Inside the CO snowline, significant depletion of CO only occurs in models with a high cosmic-ray rate. If cosmic-rays are not present in young disks, it is difficult to chemically remove carbon from CO. Additionally, removing water prior to CO depletion impedes the chemical processing of CO. Chemical processing alone cannot explain current observations of low CO abundances. Other mechanisms must also be involved.
- ID:
- ivo://CDS.VizieR/J/ApJ/745/173
- Title:
- UV absorption sight lines of LMC and SMC
- Short Name:
- J/ApJ/745/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined column densities of H I and/or H_2_ for sight lines in the Magellanic Clouds from archival Hubble Space Telescope and Far-Ultraviolet Spectroscopic Explorer spectra of H I Ly{alpha} and H_2_Lyman-band absorption. Together with some similar data from the literature, we now have absorption-based N(H I) and/or N(H_2_) for 285 Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) sight lines (114 with a detection or limit for both species) - enabling more extensive, direct, and accurate determinations of molecular fractions, gas-to-dust ratios, and elemental depletions in these two nearby, low-metallicity galaxies. For sight lines where the N(H I) estimated from 21 cm emission is significantly higher than the value derived from Ly{alpha} absorption (presumably due to emission from gas beyond the target stars), integration of the 21 cm profile only over the velocity range seen in Na I or H_2_absorption generally yields much better agreement. Conversely, N(21 cm) can be lower than N(Ly{alpha}) by factors of 2-3 in some LMC sight lines - suggestive of small-scale structure within the 21 cm beam(s) and/or some saturation in the emission. The mean gas-to-dust ratios obtained from N(H_tot_)/E(B-V) are larger than in our Galaxy, by factors of 2.8-2.9 in the LMC and 4.1-5.2 in the SMC - i.e., factors similar to the differences in metallicity. The N(H_2_)/E(B-V) ratios are more similar in the three galaxies, but with considerable scatter within each galaxy. These data may be used to test models of the atomic-to-molecular transition at low metallicities and predictions of N(H_2_) based on comparisons of 21 cm emission and the IR emission from dust.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/76
- Title:
- UV and IR properties for galaxies
- Short Name:
- J/ApJ/789/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-{beta} relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies, we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 {AA} bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 {AA} bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.
- ID:
- ivo://CDS.VizieR/J/ApJ/879/131
- Title:
- UV-FIR obs. of post-starburst galaxies & dust masses
- Short Name:
- J/ApJ/879/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive dust masses (M_dust_) from the spectral energy distributions of 58 post-starburst galaxies (PSBs). There is an anticorrelation between specific dust mass (M_dust_/M_*_) and the time elapsed since the starburst ended, indicating that dust was either destroyed, expelled, or rendered undetectable over the ~1Gyr after the burst. The M_dust_/M_*_ depletion timescale, 205_-37_^+58^Myr, is consistent with that of the CO-traced M_H2_/M_*_, suggesting that dust and gas are altered via the same process. Extrapolating these trends leads to the M_dust_/M_*_ and M_H2_/M_*_ values of early-type galaxies (ETGs) within 1-2Gyr, a timescale consistent with the evolution of other PSB properties into ETGs. Comparing Mdust and M_H2_ for PSBs yields a calibration, log M_H2_=0.45logM_dust_+6.02, that allows us to place 33 PSBs on the Kennicutt-Schmidt (KS) plane, {Sigma}SFR-{Sigma}M_H2_. Over the first ~200-300Myr, the PSBs evolve down and off of the KS relation, as their star formation rate (SFR) decreases more rapidly than M_H2_. Afterwards, M_H2_ continues to decline whereas the SFR levels off. These trends suggest that the star formation efficiency bottoms out at 10^-11^/yr and will rise to ETG levels within 0.5-1.1Gyr afterwards. The SFR decline after the burst is likely due to the absence of gas denser than the CO-traced H2. The mechanism of the M_dust_/M_*_ and M_H2_/M_*_ decline, whose timescale suggests active galactic nucleus/low-ionization nuclear emission-line region feedback, may also be preventing the large CO-traced molecular gas reservoirs from collapsing and forming denser star-forming clouds.
- ID:
- ivo://CDS.VizieR/II/114
- Title:
- UV Interstellar Extinction
- Short Name:
- II/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The documentation is mostly adapted from the "Documentation for the Machine-Readable Version of A catalog of Ultraviolet Interstellar Extinction Excesses for 1415 Stars" by Wayne H. Warren Jr., May 1986, National Space Science Data Center NSSDC/WDC-A-R&S 86-05 This document describes the machine-readable version of the catalog as it is currently being distributed from the Astronomical Data Centers. It is intended to enable users to read and process the data without problems and guesswork, but it is not intended to replace the original published paper, which users should study before processing the data. The format described below is very similar to that given on page 431 of the source reference, but some modifications were made at the ADC (with the consent of the authors) to effect uniformity.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/89
- Title:
- Variation of mid-IR extinction
- Short Name:
- J/ApJ/707/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the data obtained from the Spitzer/Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIPMSE) Legacy Program and the Two Micron All Sky Survey (2MASS) project, we derive the extinction in the four IRAC bands, [3.6], [4.5], [5.8], and [8.0]um, relative to the 2MASS Ks band (at 2.16um) for 131 GLIPMSE fields along the Galactic plane within |l|<=65{deg}, using red giants and red clump giants as tracers. As a whole, the mean extinction in the IRAC bands (normalized to the 2MASS Ks band), A_[3.6]_/A_Ks_~0.63+/-0.01, A_[4.5]_/A_Ks_~0.57+/-0.03, A_[5.8]/A_Ks_~0.49+/-0.03, A_[8.0]_/A_Ks_~0.55+/-0.03, exhibits little variation with wavelength (i.e., the extinction is somewhat flat or gray). As far as individual sightline is concerned, however, the wavelength dependence of the mid-infrared interstellar extinction A_{lambda}_/A_Ks_ varies from one sightline to another, suggesting that there may not exist a "universal" IR extinction law.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A7
- Title:
- Vela Junior (RX J0852.0-4622) HESS image
- Short Name:
- J/A+A/612/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study {gamma}-ray emission from the shell-type supernova remnant (SNR) RX J0852.0-4622 to better characterize its spectral properties and its distribution over the SNR. The analysis of an extended High Energy Spectroscopic System (H.E.S.S.) data set at very high energies (E>100GeV) permits detailed studies, as well as spatially resolved spectroscopy, of the morphology and spectrum of the whole RX J0852.0-4622 region. The H.E.S.S. data are combined with archival data from other wavebands and interpreted in the framework of leptonic and hadronic models. The joint Fermi-LAT-H.E.S.S. spectrum allows the direct determination of the spectral characteristics of the parent particle population in leptonic and hadronic scenarios using only GeV-TeV data. An updated analysis of the H.E.S.S. data shows that the spectrum of the entire SNR connects smoothly to the high-energy spectrum measured by Fermi-LAT. The increased data set makes it possible to demonstrate that the H.E.S.S. spectrum deviates significantly from a power law and is well described by both a curved power law and a power law with an exponential cutoff at an energy of E_cut_=(6.7+/-1.2_stat_+/-1.2_syst_)TeV. The joint Fermi-LAT-H.E.S.S. spectrum allows the unambiguous identification of the spectral shape as a power law with an exponential cutoff. No significant evidence is found for a variation of the spectral parameters across the SNR, suggesting similar conditions of particle acceleration across the remnant. A simple modeling using one particle population to model the SNR emission demonstrates that both leptonic and hadronic emission scenarios remain plausible. It is also shown that at least a part of the shell emission is likely due to the presence of a pulsar wind nebula around PSR J0855-4644.
- ID:
- ivo://CDS.VizieR/J/A+A/512/A83
- Title:
- Velocities of interstellar lines in Sco-Cen
- Short Name:
- J/A+A/512/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We want to make a large-scale study of the morphology, kinematics, and origin of the HI, which surrounds the Sco-Cen association. We combine our high-sensitivity southern HI survey with the Leiden/Dwingeloo Survey, considering l=240{deg}-400{deg}, b=-60{deg} to +60{deg}, and radial velocities of V=-41.8 to +40.8km/s. We point out the main HI branches surrounding the association and derive their kinematics. Kinematical HI-maps were compared with spatial maps of interstellar (IS) NaI from the literature. Upper limits for distances d were derived from optical IS absorption components from the literature. Models of expanding spherical HI shells were fitted around each stellar subgroup.
- ID:
- ivo://CDS.VizieR/J/A+A/466/949
- Title:
- Velocities of OMC-1 flows
- Short Name:
- J/A+A/466/949
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations are reported of H_2_ IR emission in the S(1) v=1-0 line at 2.121{mu}m in the Orion Molecular Cloud, OMC1, using the GriF instrument on the Canada-France-Hawaii Telescope. GriF uses a combination of adaptive optics and Fabry-Perot interferometry, yielding a spatial resolution of 0.15" to 0.18" and velocity discrimination as high as 1km/s. 193 bright H_2_ emission regions can be identified in OMC1. The general characteristics of these features are described in terms of radial velocities, brightness and spatial displacement of maxima of velocity and brightness, the latter to yield the orientation of flows in the plane of the sky. Strong spatial correlation between velocity and bright H_2_ emission is found and serves to identify many features as shocks.
