- ID:
- ivo://CDS.VizieR/J/A+A/462/507
- Title:
- AMIGA III. IRAS data
- Short Name:
- J/A+A/462/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the mid- (MIR) and far- (FIR) infrared properties of a large (~1000) sample of the most isolated galaxies in the local Universe. This sample is intended as a "nurture-free" zero point against which more environmentally influenced samples can be compared. We reprocess IRAS MIR/FIR survey data using the ADDSCAN/SCANPI utility for 1030 out of 1050 galaxies from the Catalogue of Isolated Galaxies (CIG, Cat. <VII/82>) as part of the AMIGA survey. We focus on diagnostics (FIR luminosity LFIR , R=log(LFIR/LB) and IRAS colours) thought to be sensitive to effects of environment or interaction.
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- ID:
- ivo://CDS.VizieR/J/ApJ/900/9
- Title:
- AMIGA: The Circumgalactic Medium of Andromeda
- Short Name:
- J/ApJ/900/9
- Date:
- 14 Mar 2022 07:38:05
- Publisher:
- CDS
- Description:
- Project AMIGA (Absorption Maps In the Gas of Andromeda) is a survey of the circumgalactic medium (CGM) of Andromeda (M31, R_vir_~300kpc) along 43 QSO sightlines at impact parameters 25<~R<~569kpc (25 at R<~R_vir_). We use ultraviolet absorption measurements of SiII, SiIII, SiIV, CII, and CIV from the Hubble Space Telescope/Cosmic Origins Spectrograph and OVI from the Far Ultraviolet Spectroscopic Explorer to provide an unparalleled look at how the physical conditions and metals are distributed in the CGM of M31. We find that SiIII and OVI have a covering factor near unity for R<~1.2R_vir_ and <~1.9R_vir_, respectively, demonstrating that M31 has a very extended ~104-105.5K ionized CGM. The metal and baryon masses of the 104-105.5K CGM gas within R_vir_ are >~108 and >~4x1010 (Z/0.3Z{sun})-1M{sun}, respectively. There is not much azimuthal variation in the column densities or kinematics, but there is with R. The CGM gas at R<~0.5R_vir_ is more dynamic and has more complicated, multiphase structures than at larger radii, perhaps a result of more direct impact of galactic feedback in the inner regions of the CGM. Several absorbers are projected spatially and kinematically close to M31 dwarf satellites, but we show that those are unlikely to give rise to the observed absorption. Cosmological zoom simulations of ~L* galaxies have OVI extending well beyond R_vir_ as observed for M31 but do not reproduce well the radial column density profiles of the lower ions. However, some similar trends are also observed, such as the lower ions showing a larger dispersion in column density and stronger dependence on R than higher ions. Based on our findings, it is likely that the Milky Way has a ~104-105.5K CGM as extended as for M31 and their CGM (especially the warm-hot gas probed by OVI) are overlapping.
- ID:
- ivo://CDS.VizieR/J/A+A/486/73
- Title:
- AMIGA VII. FIR and radio study
- Short Name:
- J/A+A/486/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is part of a series involving the AMIGA project (Analysis of the Interstellar Medium of Isolated GAlaxies). This project provides a statistically-significant sample of the most isolated galaxies in the northern sky. We present a study of the nuclear activity in a well-defined sample of the most isolated galaxies (total sample: n=1050, complete subsample: n=719) in the local Universe traced by their far-infrared (FIR) and radio continuum emission. We use the well-known radio continuum-FIR correlation to select radio-excess galaxies that are candidates to host an active galactic nucleus (AGN), as well as the FIR colours to find obscured AGN-candidates. We also used the existing information on nuclear activity in the Veron-Cetty catalogue and in the NASA Extragalactic Database. A final catalogue of AGN-candidate galaxies has been produced that will provide a baseline for studies on the dependence of activity on the environment. Our sample is mostly radio quiet, consistent with its high content of late-type galaxies. At most ~1.5% of the galaxies show a radio excess with respect to the radio-FIR correlation, and this fraction even goes down to less than 0.8% after rejection of back/foreground sources using FIRST. We find that the fraction of FIR colour selected AGN-candidates is ~28% with a lower limit of ~7%. Our final catalogue contains 89 AGN candidates and is publicly available on the AMIGA web page (http://www.iaa.csic.es/AMIGA.html).
- ID:
- ivo://CDS.VizieR/J/ApJ/885/64
- Title:
- Amplitude of variability for 150 YSOs in Orion
- Short Name:
- J/ApJ/885/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a quantitative, empirically based argument that at least some Class I sources are low-mass, pre-main-sequence stars surrounded by spatially extended envelopes of dusty gas. The source luminosity arises principally from stellar gravitational contraction, as in optically visible pre-main-sequence stars that lack such envelopes. We base our argument on the fact that some Class I sources in Orion and other star-forming regions have been observed by Spitzer to be periodic variables in the mid-infrared, and with periods consistent with T Tauri rotation rates. Using a radiative transfer code, we construct a variety of dust envelopes surrounding rotating, spotted stars, to see whether an envelope that produces a Class I spectral energy distribution at least broadly matches the observed modulations in luminosity. Acceptable envelopes can be either spherical or flattened and may or may not have polar cavities. The key requirement is that they have a modest equatorial optical depth at the Spitzer waveband of 3.6{mu}m, typically {tau}3.6~0.6. The total envelope mass, based on this limited study, is at most about 0.1M{sun}, less than a typical stellar mass. Future studies should focus on the dynamics of the envelope, to determine whether material is actually falling onto the circumstellar disk.
- ID:
- ivo://CDS.VizieR/III/153
- Title:
- An Atlas of Near Infrared Stellar Spectra
- Short Name:
- III/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The atlas represents a collection of spectra in the wavelength range 2.00 to 2.45 micrometers having a resolution of approximately 0.02 micrometers. The sample of 73 stars includes a supergiant, giants, dwarfs, and subdwarfs with a chemical abundance range of about -2 to +0.5 dex.
- ID:
- ivo://CDS.VizieR/J/ApJS/248/18
- Title:
- 44 and 95GHz observations of class I methanol masers
- Short Name:
- J/ApJS/248/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a simultaneous 44 and 95GHz class I methanol maser survey toward 144 sources from the 95GHz class I methanol maser catalog. The observations were made with the three telescopes of the Korean very long baseline interferometry network operating in single-dish mode. The detection rates are 89% at 44GHz and 77% at 95GHz. There are 106 new discoveries at 44GHz. Comparing the previous 95GHz detections with new observations of the same transitions made using the Purple Mountain Observatory 13.7m radio telescope shows no clear evidence of variability on a timescale of six years. Emission from the 44 and 95GHz transitions shows strong correlations in peak velocity, peak flux density, and integrated flux density, indicating that they are likely cospatial. We found that the peak flux density ratio S_pk,95_/S_pk,44_ decreases as the 44GHz peak flux density increases. We found that some class I methanol masers in our sample might be associated with infrared dark clouds, while others are associated with HII regions, indicating that some sources occur at an early stage of high-mass star formation, while others are located toward more evolved sources.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A102
- Title:
- APEX CO and HI observations of Lupus I
- Short Name:
- J/A+A/608/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lupus I cloud is found between the Upper Scorpius (USco) and Upper Centaurus-Lupus (UCL) subgroups of the Scorpius-Centaurus OB association, where the expanding USco HI shell appears to interact with a bubble currently driven by the winds of the remaining B stars of UCL. Aims. We investigate whether the Lupus I molecular could have formed in a colliding flow, and in particular, how the kinematics of the cloud might have been influenced by the larger scale gas dynamics. We performed APEX ^13^CO(2-1)and C^18^O(2-1) line observations of three distinct parts of Lupus I that provide kinematic information on the cloud at high angular and spectral resolution. We compare those results to the atomic hydrogen data from the GASS HI survey and our dust emission results presented in the previous paper. Based on the velocity information, we present a geometric model for the interaction zone between the USco shell and the UCL wind bubble. We present evidence that the molecular gas of Lupus Iis tightly linked to the atomic material of the USco shell. The CO emission in Lupus Iis found mainly at velocities between v_LSR_=3-6km/s, which is in the same range as the HI velocities. Thus, the molecular cloud is co-moving with the expanding USco atomic HI shell. The gas in the cloud shows a complex kinematic structure with several line-of-sight components that overlay each other. The nonthermal velocity dispersion is in the transonic regime in all parts of the cloud and could be injected by external compression. Our observations and the derived geometric model agree with a scenario in which Lupus Iis located in the interaction zone between the USco shell and the UCL wind bubble. The kinematics observations are consistent with a scenario in which the Lupus Icloud formed via shell instabilities. The particular location of Lupus I between USco and UCL suggests that counterpressure from the UCL wind bubble and pre-existing density enhancements, perhaps left over from the gas stream that formed the stellar subgroups, may have played a role in its formation.
- ID:
- ivo://CDS.VizieR/III/284
- Title:
- APOGEE-2 data from DR16
- Short Name:
- III/284
- Date:
- 05 Jan 2022
- Publisher:
- CDS
- Description:
- The spectral analysis and data products in Data Release 16 (DR16; 2019 December) from the high-resolution near-infrared Apache Point Observatory Galactic Evolution Experiment (APOGEE)-2/Sloan Digital Sky Survey (SDSS)-IV survey are described. Compared to the previous APOGEE data release (DR14; 2017 July), APOGEE DR16 includes about 200000 new stellar spectra, of which 100000 are from a new southern APOGEE instrument mounted on the 2.5m du Pont telescope at Las Campanas Observatory in Chile. DR16 includes all data taken up to 2018 August, including data released in previous data releases. All of the data have been re-reduced and re-analyzed using the latest pipelines, resulting in a total of 473307 spectra of 437445 stars. Changes to the analysis methods for this release include, but are not limited to, the use of MARCS model atmospheres for calculation of the entire main grid of synthetic spectra used in the analysis, a new method for filling "holes" in the grids due to unconverged model atmospheres, and a new scheme for continuum normalization. Abundances of the neutron-capture element Ce are included for the first time. A new scheme for estimating uncertainties of the derived quantities using stars with multiple observations has been applied, and calibrated values of surface gravities for dwarf stars are now supplied. Compared to DR14, the radial velocities derived for this release more closely match those in the Gaia DR2 database, and a clear improvement in the spectral analysis of the coolest giants can be seen.
- ID:
- ivo://CDS.VizieR/J/AJ/159/182
- Title:
- APOGEE Net, YSOs parameters through deep learning
- Short Name:
- J/AJ/159/182
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Machine learning allows for efficient extraction of physical properties from stellar spectra that have been obtained by large surveys. The viability of machine-learning approaches has been demonstrated for spectra covering a variety of wavelengths and spectral resolutions, but most often for main-sequence (MS) or evolved stars, where reliable synthetic spectra provide labels and data for training. Spectral models of young stellar objects (YSOs) and low-mass MS stars are less well-matched to their empirical counterparts, however, posing barriers to previous approaches to classify spectra of such stars. In this work, we generate labels for YSOs and low-mass MS stars through their photometry. We then use these labels to train a deep convolutional neural network to predict logg, Teff, and Fe/H for stars with Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra in the DR14 data set. This "APOGEE Net" has produced reliable predictions of logg for YSOs, with uncertainties of within 0.1dex and a good agreement with the structure indicated by pre-MS evolutionary tracks, and it correlates well with independently derived stellar radii. These values will be useful for studying pre-MS stellar populations to accurately diagnose membership and ages.
- ID:
- ivo://CDS.VizieR/J/ApJ/894/5
- Title:
- APOGEE2-N NIR spectra of B-type stars
- Short Name:
- J/ApJ/894/5
- Date:
- 19 Jan 2022 00:59:33
- Publisher:
- CDS
- Description:
- We present a semi-empirical spectral classification scheme for normal B-type stars using near-infrared (NIR) spectra (1.5-1.7{mu}m) from the Sloan Digital Sky Survey Apache Point Observatory Galaxy Evolution Experiment (APOGEE2)-N data release 14 (DR14) database. The main motivation for working with B-type stars is their importance in the evolution of young stellar clusters; however, we also take advantage of having a numerous sample (316 stars) of B-type star candidates in APOGEE2-N, for which we also have optical (3600-9100{AA}) counterparts from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey. By first obtaining an accurate spectral classification of the sources using the LAMOST DR3 spectra and the canonical spectral classification scheme, we found a linear relation between optical spectral types and the equivalent widths of the hydrogen lines of the Brackett series in the APOGEE2-N NIR spectra. This relation extends smoothly from a similar relation for O and early B stars found by Roman-Lopes+ (2018, J/ApJ/855/68). This way, we obtain a catalog of B-type sources with features in both the optical and NIR and a classification scheme refined down to one spectral subclass.
