- ID:
- ivo://CDS.VizieR/J/ApJ/723/993
- Title:
- Spatial extent of (U)LIRGs in the MIR. I.
- Short Name:
- J/ApJ/723/993
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the extended mid-infrared (MIR) emission of the Great Observatories All-Sky LIRG Survey sample based on 5-15um low-resolution spectra obtained with the Infrared Spectrograph on Spitzer. We calculate the fraction of extended emission (FEE) as a function of wavelength for the galaxies in the sample, FEE_{lambda}_, defined as the fraction of the emission which originates outside of the unresolved component of a source at a given distance. We find that the FEE_{lambda}_ varies from one galaxy to another, but we can identify three general types of FEE_{lambda}_: one where FEE_{lambda}_ is constant, one where features due to emission lines and polycyclic aromatic hydrocarbons appear more extended than the continuum, and a third which is characteristic of sources with deep silicate absorption at 9.7um. The mean size of the LIRG cores at 13.2um is 2.6kpc. However, once the IR luminosity of the systems reaches the threshold of L_IR_~10^11.8^L_{sun}_, slightly below the regime of Ultra-luminous Infrared Galaxies (ULIRGs), all sources become clearly more compact, with FEE_13.2um_<~0.2, and their cores are unresolved. Our estimated upper limit for the core size of ULIRGs is less than 1.5kpc.
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- ID:
- ivo://CDS.VizieR/J/ApJ/741/32
- Title:
- Spatial extent of (U)LIRGs in the MIR. II.
- Short Name:
- J/ApJ/741/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from the second part of our analysis of the extended mid-infrared (MIR) emission of the GOALS sample based on 5-14um low-resolution spectra obtained with the Infrared Spectrograph on Spitzer. We calculate the fraction of extended emission (FEE) as a function of wavelength for all galaxies in the sample, FEE_{lambda}_, defined as the fraction of the emission that originates outside of the unresolved central component of a source, and spatially separate the MIR spectrum of a galaxy into its nuclear and extended components. We find that the [NeII]12.81um emission line is as compact as the hot dust MIR continuum, while the polycyclic aromatic hydrocarbon (PAH) emission is more extended. In addition, the 6.2 and 7.7um PAH emission is more compact than that of the 11.3um PAH, which is consistent with the formers being enhanced in a more ionized medium. The presence of an active galactic nucleus (AGN) or a powerful nuclear starburst increases the compactness and the luminosity surface density of the hot dust MIR continuum, but has a negligible effect on the spatial extent of the PAH emission on kpc-scales. Furthermore, it appears that both processes, AGN and/or nuclear starburst, are indistinguishable in terms of how they modify the integrated PAH-to-continuum ratio of the FEE in (ultra)luminous infrared galaxies ((U)LIRGs). Globally, the 5-14um spectra of the extended emission component are homogeneous for all galaxies in the GOALS sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/107
- Title:
- Spatial structure of young stellar clusters. I.
- Short Name:
- J/ApJ/787/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The clusters of young stars in massive star-forming regions show a wide range of sizes, morphologies, and numbers of stars. Their highly subclustered structures are revealed by the MYStIX project's sample of 31754 young stars in nearby sites of star formation (regions at distances <3.6kpc that contain at least one O-type star.) In 17 of the regions surveyed by MYStIX, we identify subclusters of young stars using finite mixture models --collections of isothermal ellipsoids that model individual subclusters. Maximum likelihood estimation is used to estimate the model parameters, and the Akaike Information Criterion is used to determine the number of subclusters. This procedure often successfully finds famous subclusters, such as the BN/KL complex behind the Orion Nebula Cluster and the KW-object complex in M17. A catalog of 142 subclusters is presented, with 1-20 subclusters per region. The subcluster core radius distribution for this sample is peaked at 0.17pc with a standard deviation of 0.43dex, and subcluster core radius is negatively correlated with gas/dust absorption of the stars --a possible age effect. Based on the morphological arrangements of subclusters, we identify four classes of spatial structure: long chains of subclusters, clumpy structures, isolated clusters with a core-halo structure, and isolated clusters well fit by a single isothermal ellipsoid.
- ID:
- ivo://CDS.VizieR/J/AJ/162/41
- Title:
- Speckle interferometry at SOAR in 2020
- Short Name:
- J/AJ/162/41
- Date:
- 14 Mar 2022 06:54:42
- Publisher:
- CDS
- Description:
- The results of speckle interferometric observations at the 4.1m Southern Astrophysical Research Telescope in 2020, as well as earlier unpublished data, are given, totaling 1735 measurements of 1288 resolved pairs and nonresolutions of 1177 targets. We resolved for the first time 59 new pairs or subsystems in known binaries, mostly among nearby dwarf stars. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. We also report observations of 892 members of young moving groups and associations, where we resolved 103 new pairs.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A2
- Title:
- Spectra and radial velocities of nuclear stars
- Short Name:
- J/A+A/570/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Within the central 10pc of our Galaxy lies a dense cluster of stars. This nuclear star cluster forms a distinct component of the Galaxy, and similar nuclear star clusters are found in most nearby spiral and elliptical galaxies. Studying the structure and kinematics of nuclear star clusters reveals the history of mass accretion and growth of galaxy nuclei and central massive black holes. Because the Milky Way nuclear star cluster is at a distance of only 8 kpc, we can spatially resolve the cluster on sub-parsec scales. This makes the Milky Way nuclear star cluster a reference object for understanding the formation of all nuclear star clusters.
- ID:
- ivo://CDS.VizieR/J/ApJS/151/299
- Title:
- Spectra classification from ISO PHT-S database
- Short Name:
- J/ApJS/151/299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have classified over 1500 infrared spectra obtained with the PHT-S spectrometer aboard the Infrared Space Observatory according to the system developed for the Short Wavelength Spectrometer (SWS) spectra by Kraemer et al. (2002ApJS..140..389K). The majority of these spectra contribute to subclasses that are either under-represented in the SWS spectral database or contain sources that are too faint, such as M dwarfs, to have been observed by either the SWS or the Infrared Astronomical Satellite Low Resolution Spectrometer. There is strong overall agreement about the chemistry of objects observed with both instruments. Discrepancies can usually be traced to the different wavelength ranges and sensitivities of the instruments. Finally, a large subset of the observations (~250 spectra) exhibit a featureless, red continuum that is consistent with emission from zodiacal dust and suggest directions for further analysis of this serendipitous measurement of the zodiacal background.
- ID:
- ivo://CDS.VizieR/J/A+A/465/993
- Title:
- Spectral atlas of massive stars around He I
- Short Name:
- J/A+A/465/993
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a digital atlas of peculiar, high-luminosity massive stars in the near-infrared region (10470-11000{AA}) at medium resolution (R~7000). The spectra are centered around HeI 10830{AA}, which is formed in the wind of those stars, and is a crucial line to obtain their physical parameters. The instrumental configuration also sampled a rich variety of emission lines of FeII, MgII, CI, NI, and Pa{gamma}. Secure identifications for most spectral lines are given, based on synthetic atmosphere models calculated by our group. We also propose that two unidentified absorption features have interstellar and/or circumstellar origin. For the strongest one (10780{AA}) an empirical calibration between E(B-V) and equivalent width is provided. The atlas displays the spectra of massive stars organized in four categories, namely Be stars, OBA Iape (or luminous blue variables, LBV candidates and ex/dormant LBVs), OB supergiants and Wolf-Rayet stars. For comparison, the photospheric spectra of non emission-line stars are presented. Selected LBVs were observed in different epochs from 2001 to 2004, and their spectral variability reveals that some stars, such as eta Car, AG Car and HR Car, suffered dramatic spectroscopic changes during this time interval.
- ID:
- ivo://CDS.VizieR/J/A+AS/123/135
- Title:
- Spectral classifications of 180 IR stars
- Short Name:
- J/A+AS/123/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 180 supposedly composite-spectrum stars has been studied on the basis of spectra obtained in the near infrared (8370-8780{AA}) at a dispersion of 33{AA}/mm. The objective was to study the cooler components of the systems. Of our sample, 120 are true composite spectra, 35 are hot spectra of types B, F and 25 are Am stars. We find a strong concentration of the cooler components of the composite spectra around G8III. In view of the difficulty of classifying composite spectra, because of the superposition of an early type dwarf and a late type giant or supergiant spectrum, we have made several tests to control the classification based upon the infrared region. Since all tests gave positive results, we conclude that our classifications can be considered as being both reliable and homogeneous.
- ID:
- ivo://CDS.VizieR/J/A+AS/133/201
- Title:
- Spectral class of unidentified IRAS sources
- Short Name:
- J/A+AS/133/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M spectral types and IRAS infrared magnitudes, colors, and variability parameters are given for 155 largely unidentified IRAS point sources having quality-3 flux densities at 12, 25, and 60 mum.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A37
- Title:
- Spectral cube toward NGC 6334 I and I(N)
- Short Name:
- J/A+A/593/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HF molecule has been proposed as a sensitive tracer of diffuse interstellar gas, while at higher densities its abundance could be influenced heavily by freeze-out onto dust grains. We investigate the spatial distribution of a collection of absorbing gas clouds, some associated with the dense, massive star-forming core NGC 6334 I, and others with diffuse foreground clouds elsewhere along the line of sight. For the former category, we aim to study the dynamical properties of the clouds in order to assess their potential to feed the accreting protostellar cores. We use far-infrared spectral imaging from the Herschel SPIRE iFTS to construct a map of HF absorption at 243um in a 6'x3.5' region surrounding NGC 6334 I and I(N).
