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6231. Spitzer/IRAC sources in the EGS I. SEDs
ID:
ivo://CDS.VizieR/J/ApJS/193/13
Title:
Spitzer/IRAC sources in the EGS I. SEDs
Short Name:
J/ApJS/193/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an IRAC 3.6+4.5um selected catalog in the Extended Groth Strip (EGS) containing photometry from the ultraviolet to the far-infrared and stellar parameters derived from the analysis of the multi-wavelength data. In this paper, we describe the method used to build coherent spectral energy distributions (SEDs) for all the sources. In a forthcoming companion paper, we analyze those SEDs to obtain robust estimations of stellar parameters such as photometric redshifts, stellar masses, and star formation rates. The catalog comprises 76936 sources with [3.6]<=23.75mag (85% completeness level of the IRAC survey in the EGS) over 0.48deg^2^. For approximately 16% of this sample, we are able to deconvolve the IRAC data to obtain robust fluxes for the multiple counterparts found in ground-based optical images. Typically, the SEDs of the IRAC sources in our catalog count with more than 15 photometric data points, spanning from the ultraviolet wavelengths probed by GALEX to the far-infrared observed by Spitzer, and going through ground- and space-based optical and near-infrared data taken with 2-8m class telescopes. Approximately 95% and 90% of all IRAC sources are detected in the deepest optical and near-infrared bands. These fractions are reduced to 85% and 70% for S/N>5 detections in each band. Only 10% of the sources in the catalog have optical spectroscopy and redshift estimations. Almost 20% and 2% of the sources are detected by MIPS at 24 and 70um, respectively. We also cross-correlate our catalog with public X-ray and radio catalogs.
6232. Spitzer IRAC survey of the galactic center
ID:
ivo://CDS.VizieR/II/295
Title:
Spitzer IRAC survey of the galactic center
Short Name:
II/295
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained Spitzer IRAC observations of the central 2.0{deg}x1.4{deg} (~280x200pc) of the Galaxy at 3.6-8.0um. A point-source catalog of 1065565 objects is presented. The catalog includes magnitudes for the point sources at 3.6, 4.5, 5.8, and 8.0um, as well as JHKs photometry from Two Micron All Sky Survey (2MASS). The point-source catalog is confusion limited with average limits of 12.4, 12.1, 11.7, and 11.2mag for [3.6], [4.5], [5.8], and [8.0], respectively. We find that the confusion limits are spatially variable because of stellar surface density, background surface brightness level, and extinction variations across the survey region. The overall distribution of point-source density with Galactic latitude and longitude is essentially constant, but structure does appear when sources of different magnitude ranges are selected. Bright stars show a steep decreasing gradient with Galactic latitude and a slow decreasing gradient with Galactic longitude, with a peak at the position of the Galactic center. From IRAC color-magnitude and color-color diagrams, we conclude that most of the point sources in our catalog have IRAC magnitudes and colors characteristic of red giant and asymptotic giant branch (AGB) stars.
6233. Spitzer/IRAC variability survey of Bootes field
ID:
ivo://CDS.VizieR/J/ApJ/817/119
Title:
Spitzer/IRAC variability survey of Bootes field
Short Name:
J/ApJ/817/119
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Decadal IRAC Bootes Survey is a mid-IR variability survey of the ~9deg^2^ of the NDWFS Bootes Field and extends the time baseline of its predecessor, the Spitzer Deep, Wide-Field Survey (SDWFS), from 4 to 10 years. The Spitzer Space Telescope visited the field five times between 2004 and 2014 at 3.6 and 4.5{mu}m. We provide the difference image analysis photometry for a half a million mostly extragalactic sources. In mid-IR color-color plane, sources with quasar colors constitute the largest variability class (75%), 16% of the variable objects have stellar colors and the remaining 9% have the colors of galaxies. Adding the fifth epoch doubles the number of variable active galactic nuclei (AGNs) for the same false positive rates as in SDWFS, or increases the number of sources by 20% while decreasing the false positive rates by factors of 2-3 for the same variability amplitude. We quantify the ensemble mid-IR variability of ~1500 spectroscopically confirmed AGNs using single power-law structure functions (SFs), which we find to be steeper (index {gamma}~0.45) than in the optical ({gamma}~0.3), leading to much lower amplitudes at short time-lags. This provides evidence for large emission regions, smoothing out any fast UV/optical variations, as the origin of infrared quasar variability. The mid-IR AGN SF slope {gamma} seems to be uncorrelated with both the luminosity and rest-frame wavelength, while the amplitude shows an anti-correlation with the luminosity and a correlation with the rest-frame wavelength.
6234. Spitzer/IRAC view of Sh2-284
ID:
ivo://CDS.VizieR/J/A+A/503/107
Title:
Spitzer/IRAC view of Sh2-284
Short Name:
J/A+A/503/107
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using Spitzer/IRAC observations of a region to be observed by the CoRoT satellite, we have unraveled a new complex star-forming region at low metallicity in the outer Galaxy. We perform a study of S284 in order to outline the chain of events in this star-forming region.
6235. Spitzer IRDCs
ID:
ivo://CDS.VizieR/J/ApJ/698/324
Title:
Spitzer IRDCs
Short Name:
J/ApJ/698/324
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have conducted a survey of a sample of infrared-dark clouds (IRDCs) with the Spitzer Space Telescope in order to explore their mass distribution. We present a method for tracing mass using dust absorption against the bright Galactic background at 8um. The IRDCs in this sample are comprised of tens of clumps, ranging in sizes from 0.02 to 0.3pc in diameter and masses from 0.5 to a few 10^3^M_{sun}_, the broadest dynamic range in any clump mass spectrum study to date.
6236. Spitzer IR excesses in A-K stars
ID:
ivo://CDS.VizieR/J/ApJ/775/55
Title:
Spitzer IR excesses in A-K stars
Short Name:
J/ApJ/775/55
Date:
21 Oct 2021
Publisher:
CDS
Description:
Cold debris disks trace the limits of planet formation or migration in the outer regions of planetary systems, and thus have the potential to answer many of the outstanding questions in wide-orbit planet formation and evolution. We characterized the infrared excess spectral energy distributions of 174 cold debris disks around 546 main-sequence stars observed by both the Spitzer Infrared Spectrograph and the Multiband Imaging Photometer for Spitzer. We found a trend between the temperature of the inner edges of cold debris disks and the stellar type of the stars they orbit. This argues against the importance of strictly temperature-dependent processes (e.g., non-water ice lines) in setting the dimensions of cold debris disks. Also, we found no evidence that delayed stirring causes the trend. The trend may result from outward planet migration that traces the extent of the primordial protoplanetary disk, or it may result from planet formation that halts at an orbital radius limited by the efficiency of core accretion.
6237. Spitzer/IRS debris disk catalog. I.
ID:
ivo://CDS.VizieR/J/ApJS/211/25
Title:
Spitzer/IRS debris disk catalog. I.
Short Name:
J/ApJS/211/25
Date:
21 Oct 2021
Publisher:
CDS
Description:
During the Spitzer Space Telescope cryogenic mission, Guaranteed Time Observers, Legacy Teams, and General Observers obtained Infrared Spectrograph (IRS) observations of hundreds of debris disk candidates. We calibrated the spectra of 571 candidates, including 64 new IRAS and Multiband Imaging Photometer for Spitzer (MIPS) debris disks candidates, modeled their stellar photospheres, and produced a catalog of excess spectra for unresolved debris disks. For 499 targets with IRS excess but without strong spectral features (and a subset of 420 targets with additional MIPS 70{mu}m observations), we modeled the IRS (and MIPS data) assuming that the dust thermal emission was well-described using either a one- or two-temperature blackbody model. We calculated the probability for each model and computed the average probability to select among models. We found that the spectral energy distributions for the majority of objects (~66%) were better described using a two-temperature model with warm (T_gr_~100-500K) and cold (T_gr_~50-150K) dust populations analogous to zodiacal and Kuiper Belt dust, suggesting that planetary systems are common in debris disks and zodiacal dust is common around host stars with ages up to ~1Gyr. We found that younger stars generally have disks with larger fractional infrared luminosities and higher grain temperatures and that higher-mass stars have disks with higher grain temperatures. We show that the increasing distance of dust around debris disks is inconsistent with self-stirred disk models, expected if these systems possess planets at 30-150AU. Finally, we illustrate how observations of debris disks may be used to constrain the radial dependence of material in the minimum mass solar nebula.
6238. Spitzer/IRS debris disk catalog. II.
ID:
ivo://CDS.VizieR/J/ApJ/798/87
Title:
Spitzer/IRS debris disk catalog. II.
Short Name:
J/ApJ/798/87
Date:
21 Oct 2021
Publisher:
CDS
Description:
During the Spitzer Space Telescope cryogenic mission, astronomers obtained Infrared Spectrograph (IRS) observations of hundreds of debris disk candidates that have been compiled in the Spitzer IRS Debris Disk Catalog (Chen et al. 2014, J/ApJS/211/25). We have discovered 10 and/or 20 {mu}m silicate emission features toward 120 targets in the catalog and modeled the IRS spectra of these sources, consistent with MIPS 70 {mu}m observations, assuming that the grains are composed of silicates (olivine, pyroxene, forsterite, and enstatite) and are located either in a continuous disk with power-law size and surface density distributions or thin rings that are well-characterized using two separate dust grain temperatures. For systems better fit by the continuous disk model, we find that (1) the dust size distribution power-law index is consistent with that expected from a collisional cascade, q=3.5-4.0, with a large number of values outside this range, and (2) the minimum grain size, a_min_, increases with stellar luminosity, L_*_, but the dependence of a_min_ on L_*_ is weaker than expected from radiation pressure alone. In addition, we also find that (3) the crystalline fraction of dust in debris disks evolves as a function of time with a large dispersion in crystalline fractions for stars of any particular stellar age or mass, (4) the disk inner edge is correlated with host star mass, and (5) there exists substantial variation in the properties of coeval disks in Sco-Cen, indicating that the observed variation is probably due to stochasticity and diversity in planet formation.
6239. Spitzer/IRS obs. of Magellanic carbon stars
ID:
ivo://CDS.VizieR/J/ApJ/826/44
Title:
Spitzer/IRS obs. of Magellanic carbon stars
Short Name:
J/ApJ/826/44
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Infrared Spectrograph on the Spitzer Space Telescope observed 184 carbon stars in the Magellanic Clouds. This sample reveals that the dust-production rate (DPR) from carbon stars generally increases with the pulsation period of the star. The composition of the dust grains follows two condensation sequences, with more SiC condensing before amorphous carbon in metal-rich stars, and the order reversed in metal-poor stars. MgS dust condenses in optically thicker dust shells, and its condensation is delayed in more metal-poor stars. Metal-poor carbon stars also tend to have stronger absorption from C_2_H_2_ at 7.5{mu}m. The relation between DPR and pulsation period shows significant apparent scatter, which results from the initial mass of the star, with more massive stars occupying a sequence parallel to lower-mass stars, but shifted to longer periods. Accounting for differences in the mass distribution between the carbon stars observed in the Small and Large Magellanic Clouds reveals a hint of a subtle decrease in the DPR at lower metallicities, but it is not statistically significant. The most deeply embedded carbon stars have lower variability amplitudes and show SiC in absorption. In some cases they have bluer colors at shorter wavelengths, suggesting that the central star is becoming visible. These deeply embedded stars may be evolving off of the asymptotic giant branch and/or they may have non-spherical dust geometries.
6240. Spitzer-IRS study of massive YSOs in galactic center
ID:
ivo://CDS.VizieR/J/ApJ/736/133
Title:
Spitzer-IRS study of massive YSOs in galactic center
Short Name:
J/ApJ/736/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from our spectroscopic study, using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope, designed to identify massive young stellar objects (YSOs) in the Galactic center (GC). Our sample of 107 YSO candidates was selected based on Infrared Array Camera (IRAC) colors from the high spatial resolution, high sensitivity Spitzer/IRAC images in the Central Molecular Zone, which spans the central ~300pc region of the Milky Way. We obtained IRS spectra over 5-35um using both high- and low-resolution IRS modules. We spectroscopically identify massive YSOs by the presence of a 15.4um shoulder on the absorption profile of 15um CO_2_ ice, suggestive of CO_2_ ice mixed with CH_3_OH ice on grains. This 15.4um shoulder is clearly observed in 16 sources and possibly observed in an additional 19 sources. We show that nine massive YSOs also reveal molecular gas-phase absorption from CO_2_, C_2_H_2_, and/or HCN, which traces warm and dense gas in YSOs. Our results provide the first spectroscopic census of the massive YSO population in the GC. We fit YSO models to the observed spectral energy distributions and find YSO masses of 8-23M_{sun}_, which generally agree with the masses derived from observed radio continuum emission. We find that about 50% of photometrically identified YSOs are confirmed with our spectroscopic study. This implies a preliminary star formation rate of ~0.07M_{sun}/yr at the GC.