- ID:
- ivo://CDS.VizieR/J/MNRAS/395/1695
- Title:
- Spitzer mid-IR spectroscopy of LIRGs
- Short Name:
- J/MNRAS/395/1695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results on low-resolution mid-infrared (MIR) spectra of 70 IR-luminous galaxies obtained with the infrared spectrograph (IRS) onboard Spitzer. We selected sources from the European Large Area Infrared Survey with S_15_>0.8mJy and photometric or spectroscopic z>1. About half of the samples are quasi-stellar objects (QSOs) in the optical, while the remaining sources are galaxies, comprising both obscured active galactic nuclei (AGN) and starbursts. Redshifts were obtained from optical spectroscopy, photometric redshifts and the IRS spectra. The later turn out to be reliable for obscured and/or star-forming sources, thus becoming an ideal complement to optical spectroscopy for redshift estimation.
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- ID:
- ivo://CDS.VizieR/J/ApJ/658/778
- Title:
- Spitzer mid-IR spectroscopy of z~2 ULIRGs
- Short Name:
- J/ApJ/658/778
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the mid-infrared spectra obtained with the Spitzer IRS for 52 sources, selected as infrared luminous, z>~1 candidates in the Extragalactic First Look Survey (XFLS). The sample selection criteria are F24um>~0.9mJy, vFv(24um)/vFv(8um)>~3.16, and vFv(24um)/vFv(0.7um)>~10. Of the 52 spectra, 47 (90%) produced measurable redshifts based solely on the mid-IR spectral features, with 35/47 (74%) at 1.5<~z<~3.2. Keck spectroscopy of a subsample (17/47) agrees with the mid-IR redshift measurements. The observed spectra fall into three categories: (1) 33% (17/52) have strong PAH emission and are probably powered by star formation with total IR luminosity roughly a factor of 5 higher than the local starburst ULIRGs; (2) 33% (17/52) have only deep silicate absorption at 9.8um, indicating deeply embedded dusty systems -these data alone cannot determine the energetic nature of the heating sources in these systems; and (3) the remaining 34% are mid-IR continuum-dominated systems with weak PAH emission and/or silicate absorption. This subsample is probably AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJS/208/24
- Title:
- Spitzer MIR AGN survey. I.
- Short Name:
- J/ApJS/208/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a program of optical and near-infrared spectroscopic follow-up of candidate active galactic nuclei (AGNs) selected in the mid-infrared. This survey selects both normal and obscured AGNs closely matched in luminosity across a wide range, from Seyfert galaxies with bolometric luminosities L _bol_~10^10^L_{sun}_ to highly luminous quasars (L_bol_~10^14^L_{sun}_), all with redshifts ranging from 0 to 4.3. Samples of candidate AGNs were selected with mid-infrared color cuts at several different 24{mu}m flux density limits to ensure a range of luminosities at a given redshift. The survey consists of 786 candidate AGNs and quasars, of which 672 have spectroscopic redshifts and classifications. Of these, 137 (20%) are type 1 AGNs with blue continua, 294 (44%) are type 2 objects with extinctions A_V_>~5 toward their AGNs, 96 (14%) are AGNs with lower extinctions (A_V_~1), and 145 (22%) have redshifts, but no clear signs of AGN activity in their spectra. Of the survey objects 50% have L_bol_>10^12^L_{sun}_, in the quasar regime. We present composite spectra for type 2 quasars and objects with no signs of AGN activity in their spectra. We also discuss the mid-infrared - emission-line luminosity correlation and present the results of cross correlations with serendipitous X-ray and radio sources.
- ID:
- ivo://CDS.VizieR/J/AJ/141/1
- Title:
- Spitzer observations of GOODS fields
- Short Name:
- J/AJ/141/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer 16um imaging of the Great Observatories Origins Deep Survey (GOODS) fields. We survey 150 arcmin^2^ in each of the two GOODS fields (North and South), to an average 3{sigma} depth of 40 and 65uJy, respectively. We detect ~1300 sources in both fields combined. We validate the photometry using the 3-24um spectral energy distribution of stars in the fields compared to Spitzer spectroscopic templates. Comparison with ISOCAM and AKARI observations in the same fields shows reasonable agreement, though the uncertainties are large. We provide a catalog of photometry, with sources cross-correlated with available Spitzer, Chandra, and Hubble Space Telescope data. Galaxy number counts show good agreement with previous results from ISOCAM and AKARI with improved uncertainties.
- ID:
- ivo://CDS.VizieR/J/ApJ/713/330
- Title:
- Spitzer observations of major-merger galaxies
- Short Name:
- J/ApJ/713/330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer observations for a sample of close major-merger galaxy pairs (KPAIR sample) selected from cross-matches between the 2MASS Extended Source Catalog and Sloan Digital Sky Survey Data Release 3. The goals are to study the star formation activity in these galaxies and to set a local bench mark for the cosmic evolution of close major mergers. The Spitzer KPAIR sample (27 pairs, 54 galaxies) includes all spectroscopically confirmed spiral-spiral (S+S) and spiral-elliptical (S+E) pairs in a parent sample that is complete for primaries brighter than K=12.5 mag, projected separations of 5h^-1^kpc<=s<=20h^-1^kpc, and mass ratios <=2.5. The Spitzer data, consisting of images in seven bands (3.6, 4.5, 5.8, 8, 24, 70, 160um), show very diversified IR emission properties.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/79
- Title:
- Spitzer observations of radio-loud AGNs (CARLA)
- Short Name:
- J/ApJ/769/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first results from the Clusters Around Radio-Loud AGN program, a Cycle 7 and 8 Spitzer Space Telescope snapshot program to investigate the environments of a large sample of obscured and unobscured luminous radio-loud active galactic nuclei (AGNs) at 1.2<z<3.2. These data, obtained for 387 fields, reach 3.6 and 4.5{mu}m depths of [3.6]_AB_=22.6 and [4.5]_AB_=22.9 at the 95% completeness level, which is two to three times fainter than L* in this redshift range. By using the color cut [3.6]-[4.5]>-0.1 (AB), which efficiently selects high-redshift (z>1.3) galaxies of all types, we identify galaxy cluster member candidates in the fields of the radio-loud AGN. The local density of these Infrared Array Camera (IRAC)-selected sources is compared to the density of similarly selected sources in blank fields. We find that 92% of the radio-loud AGN reside in environments richer than average. The majority (55%) of the radio-loud AGN fields are found to be overdense at a>=2{sigma} level; 10% are overdense at a>=5{sigma} level. A clear rise in surface density of IRAC-selected sources toward the position of the radio-loud AGN strongly supports an association of the majority of the IRAC-selected sources with the radio-loud AGN. Our results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-redshift galaxy (proto-)clusters. We investigate how environment depends on AGN type (unobscured radio-loud quasars versus obscured radio galaxies), radio luminosity and redshift, finding no correlation with either AGN type or radio luminosity. We find a decrease in density with redshift, consistent with galaxy evolution for this uniform, flux-limited survey. These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/664/850
- Title:
- Spitzer observations of stars in M33
- Short Name:
- J/ApJ/664/850
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze five epochs of Spitzer Space Telescope Infrared Array Camera (IRAC) observations of the nearby spiral galaxy M33. Each epoch covered nearly a square degree at 3.6, 4.5, and 8.0um. The point-source catalog from the full data set contains 37650 stars. The stars have luminosities characteristic of the asymptotic giant branch and can be separated into oxygen-rich and carbon-rich populations by their [3.6]-[4.5] colors. The [3.6]-[8.0] colors indicate that over 80% of the stars detected at 8.0um have dust shells. Photometric comparison of epochs using conservative criteria yields a catalog of 2923 variable stars. These variables are most likely long-period variables amid an evolved stellar population. At least one-third of the identified carbon stars are variable.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/39
- Title:
- Spitzer observations of W3 molecular cloud
- Short Name:
- J/ApJ/743/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we have carried out an in-depth analysis of the young stellar content in the W3 giant molecular cloud (GMC). The young stellar object (YSO) population was identified and classified in the Infrared Array Camera/Multiband Imaging Photometer color-magnitude space according to the "Class" scheme and compared to other classifications based on intrinsic properties. Class 0/I and II candidates were also compared to low-/intermediate-mass pre-main-sequence (PMS) stars selected through their colors and magnitudes in the Two Micron All Sky Survey. We find that a reliable color/magnitude selection of low-mass PMS stars in the infrared requires prior knowledge of the protostar population, while intermediate-mass objects can be more reliably identified. By means of the minimum spanning tree algorithm and our YSO spatial distribution and age maps, we investigated the YSO groups and the star formation history in W3.
- ID:
- ivo://CDS.VizieR/J/MNRAS/389/1150
- Title:
- Spitzer photometry of globulars in 2 galaxies
- Short Name:
- J/MNRAS/389/1150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spitzer IR Array Camera (IRAC) mid-infrared photometry is presented for the globular cluster (GC) systems of the NGC 5128 ('Centaurus A') and NGC 4594 ('Sombrero') galaxies. Existing optical photometric and spectroscopic are combined with this new data in a comprehensive optical-to-mid-IR colour catalogue of 260 GCs. Empirical colour-metallicity relationships are derived for all optical-to-mid-IR colour combinations.
- ID:
- ivo://CDS.VizieR/J/A+A/476/1161
- Title:
- Spitzer photometry of M33
- Short Name:
- J/A+A/476/1161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining the relative vicinity of the Local Group spiral galaxy M33 with the Spitzer images, we investigate the properties of infrared (IR) emission sites and assess the reliability of the IR emission as a star formation tracer. The mid- and far-IR emission of M33 was obtained from IRAC and MIPS images from the Spitzer archive. We compared the photometric results for several samples of three known types of discrete sources (HII regions, supernovae remnants and planetary nebulae) with theoretical diagnostic diagrams, and derived the spectral energy distribution (from 3.6 to 24{mu}m) of each type of object. Moreover, we generated a catalogue of 24{mu}m sources and inferred their nature from the observed and theoretical colours of the known type sources. We estimated the star formation rate in M33 both globally and locally, from the IR emission and from the Halpha emission line.
