- ID:
- ivo://CDS.VizieR/J/AJ/145/66
- Title:
- Spitzer light curves of YSOs in IC 348
- Short Name:
- J/AJ/145/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on synoptic observations at 3.6 and 4.5{mu}m of young stellar objects in IC 348 with 38epochs covering 40days. We find that among the detected cluster members, 338 at [3.6] and 269 at both [3.6] and [4.5], many are variable on daily to weekly timescales with typical fluctuations of ~0.1mag. The fraction of variables ranges from 20% for the diskless pre-main sequence stars to 60% for the stars still surrounded by infalling envelopes. We also find that stars in the exposed cluster core are less variable than the stars in the dense, slightly younger, southwestern ridge. This trend persists even after accounting for the underlying correlation with infrared spectral energy distribution type, suggesting that the change in variable fraction is not simply a reflection of the change in relative fraction of class I versus class II sources across the cloud, but instead reflects a change in variability with age. We also see a strong correlation between infrared variability and X-ray luminosity among the class II sources. The observed variability most likely reflects large changes in the structure of the inner wall located at the dust sublimation radius. We explore the possibility that these structural perturbations could be caused by a hot spot on the star heating dust above the sublimation temperature, causing it to evaporate rapidly, and increasing the inner radius for a portion of the disk. Under a number of simplifying assumptions we show that this model can reproduce the size and timescale of the 3.6 and 4.5{mu}m fluctuations. Regardless of its source, the infrared variability indicates that the inner disk is not a slowly evolving entity, but instead is a bubbling, warped, dented mass of gas and dust whose global size and shape fluctuate in a matter of days.
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- ID:
- ivo://CDS.VizieR/J/AJ/144/31
- Title:
- Spitzer+2MASS photometry of protostar candidates
- Short Name:
- J/AJ/144/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify protostars in Spitzer surveys of nine star-forming (SF) molecular clouds within 1kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. These clouds encompass a variety of SF environments, including both low-mass and high-mass SF regions, as well as dense clusters and regions of sparsely distributed star formation. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine near- and mid-infrared photometry from the Two Micron All Sky Survey and Spitzer to create 1-24{mu}m spectral energy distributions (SEDs). Using protostars from the c2d survey with well-determined bolometric luminosities, we derive a relationship between bolometric luminosity, mid-IR luminosity (integrated from 1-24{mu}m), and SED slope. Estimations of the bolometric luminosities for protostar candidates are combined to create luminosity functions for each cloud. Contamination due to edge-on disks, reddened Class II sources, and galaxies is estimated and removed from the luminosity functions. We find that luminosity functions for high-mass SF clouds (Orion, Mon R2, and Cep OB3) peak near 1L_{sun}_ and show a tail extending toward luminosities above 100L_{sun}_. The luminosity functions of the low-mass SF clouds (Serpens, Perseus, Ophiuchus, Taurus, Lupus, and Chamaeleon) do not exhibit a common peak, however the combined luminosity function of these regions peaks below 1L_{sun}_. Finally, we examine the luminosity functions as a function of the local surface density of young stellar objects. In the Orion molecular clouds, we find a significant difference between the luminosity functions of protostars in regions of high and low stellar density, the former of which is biased toward more luminous sources. This may be the result of primordial mass segregation, although this interpretation is not unique. We compare our luminosity functions to those predicted by models and find that our observed luminosity functions are best matched by models that invoke competitive accretion, although we do not find strong agreement between the high-mass SF clouds and any of the models.
- 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.
- 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/AJ/138/1261
- Title:
- Spitzer/MIPS observations of the COSMOS field
- Short Name:
- J/AJ/138/1261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer 70 and 160um observations of the COSMOS Spitzer survey (S-COSMOS). The data processing techniques are discussed for the publicly released products consisting of images and source catalogs. We present accurate 70 and 160um source counts of the COSMOS field and find reasonable agreement with measurements in other fields and with model predictions. The previously reported counts for GOODS-North and the extragalactic First Look Survey are updated with the latest calibration, and counts are measured based on the large area SWIRE survey to constrain the bright source counts. We measure an extragalactic confusion noise level of {sigma}_c_=9.4+/-3.3mJy (q=5) for the MIPS 160um band based on the deep S-COSMOS data and report an updated confusion noise level of {sigma}_c_=0.35+/-0.15mJy (q=5) for the MIPS 70um band.
- 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/ApJ/653/675
- Title:
- Spitzer 24{mu}m photometry of A dwarfs
- Short Name:
- J/ApJ/653/675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 24 and/or 70um measurements of ~160 A-type main-sequence stars using the Multiband Imaging Photometer for Spitzer (MIPS).
- ID:
- ivo://CDS.VizieR/J/ApJ/620/1010
- Title:
- Spitzer 24{mu}m photometry of A dwarfs
- Short Name:
- J/ApJ/620/1010
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new Spitzer 24{mu}m photometry of 76 main-sequence A-type stars. We combine these results with previously reported Spitzer 24{mu}m data and 24 and 25{mu}m photometry from the Infrared Space Observatory and the Infrared Astronomy Satellite. The result is a sample of 266 stars with mass close to 2.5M_Sun_ all detected to at least the ~7{sigma} level relative to their photospheric emission.
- ID:
- ivo://CDS.VizieR/J/AJ/144/135
- Title:
- Spitzer 24{mu}m photometry of Hipparcos F stars
- Short Name:
- J/AJ/144/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a study of debris disks around F stars in order to explore correlations between rotation, stellar winds, and circumstellar disks. We obtained new 24{mu}m photometry from the Multiband Imaging Photometer for Spitzer (MIPS) camera for a sample of 188 relatively nearby F dwarfs with various rotation rates and optical colors, and combined it with archival MIPS data for 66 more F stars, as well as Wide-field Infrared Survey Explorer data for the entire sample, plus 9 more F stars. Based on the objects' K_s_-[24] and [3.4]-[22] colors, we identify 22 stars in our sample as having 22 and/or 24{mu}m excesses above our detection limit, 13 of which are new discoveries. Our overall disk detection rate is 22/263, or 8%, consistent with previous determinations of disk fractions in the solar neighborhood. While fast-rotating stars are expected to have strong winds capable of efficiently removing dust, we find no correlation between rotational velocity and infrared excess. Similarly, we find no significant difference in excess detection rate between late-type F stars, which have convective surfaces, and early-type F stars, which have fully radiative envelopes. However, the essentially unknown range of ages in this sample may be washing out any effects relating rotation, winds, and disks.
- 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.