- 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.
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- ID:
- ivo://CDS.VizieR/J/ApJ/646/297
- Title:
- Spitzer observations of pre-main-sequence stars
- Short Name:
- J/ApJ/646/297
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Early observations of T Tauri stars suggested that stars with evidence of circumstellar accretion disks rotated slower than stars without such evidence, but more recent results are not as clear. Near-IR circumstellar disk indicators, although the most widely available, are subject to uncertainties that can result from inner disk holes and/or the system inclination. Mid-infrared observations are less sensitive to such effects, but until now, these observations have been difficult to obtain. The Spitzer Space Telescope now easily enables mid-infrared measurements of large samples of PMS stars covering a broad mass range in nearby star-forming regions. Megeath and collaborators surveyed the Orion Molecular Clouds (1Myr) with the IRAC instrument (3.6, 4.5, 5.8, 8um) as part of a joint IRAC and MIPS GTO program. We examine the relationship between rotation and Spitzer mid-IR fluxes for 900 stars in Orion for stars between 3 and 0.1M_{sun}_. We find in these Spitzer data the clearest indication to date that stars with longer periods are more likely than those with short periods to have IR excesses suggestive of disks.
- 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/662/1067
- Title:
- Spitzer observations of sigma Orionis
- Short Name:
- J/ApJ/662/1067
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new Spitzer Space Telescope observations, using the IRAC and MIPS instruments, of the young (~3Myr) sigma Orionis cluster. We identify 336 stars as members of the cluster, using optical and near-infrared color-magnitude diagrams. Using the spectral energy distribution slopes in the IRAC spectral range, we place objects into several classes: non-excess stars, stars with optically thick disks (such as classical T Tauri stars), class I (protostellar) candidates, and stars with "evolved disks"; the last exhibit smaller IRAC excesses than optically thick disk systems. In general, this classification agrees with the location expected in IRAC-MIPS color-color diagrams for these objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/845/120
- Title:
- Spitzer obs. of warm dust in 83 debris disks
- Short Name:
- J/ApJ/845/120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The architectures of debris disks encode the history of planet formation in these systems. Studies of debris disks via their spectral energy distributions (SEDs) have found infrared excesses arising from cold dust, warm dust, or a combination of the two. The cold outer belts of many systems have been imaged, facilitating their study in great detail. Far less is known about the warm components, including the origin of the dust. The regularity of the disk temperatures indicates an underlying structure that may be linked to the water snow line. If the dust is generated from collisions in an exo-asteroid belt, the dust will likely trace the location of the water snow line in the primordial protoplanetary disk where planetesimal growth was enhanced. If instead the warm dust arises from the inward transport from a reservoir of icy material farther out in the system, the dust location is expected to be set by the current snow line. We analyze the SEDs of a large sample of debris disks with warm components. We find that warm components in single-component systems (those without detectable cold components) follow the primordial snow line rather than the current snow line, so they likely arise from exo-asteroid belts. While the locations of many warm components in two-component systems are also consistent with the primordial snow line, there is more diversity among these systems, suggesting additional effects play a role.
- ID:
- ivo://CDS.VizieR/J/ApJ/643/965
- Title:
- Spitzer photometry of the Trifid nebula (M20)
- Short Name:
- J/ApJ/643/965
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spitzer IRAC and MIPS images of the Trifid Nebula (M20) reveal its spectacular appearance in infrared light, highlighting the nebula's special evolutionary stage. The images feature recently formed massive protostars and numerous young stellar objects, and a single O star that illuminates the surrounding molecular cloud from which it formed, and unveil large-scale, filamentary dark clouds. Multiple protostars are detected in the infrared, within the cold dust cores of TC3 and TC4, which were previously defined as Class 0. The cold dust continuum cores of TC1 and TC2 contain only one protostar each. The Spitzer color-color diagram allowed us to identify 160 young stellar objects (YSOs) and classify them into different evolutionary stages. The diagram also revealed a unique group of YSOs that are bright at 24um but have the spectral energy distribution peaking at 58um.
- ID:
- ivo://CDS.VizieR/J/A+A/517/A44
- Title:
- Spitzer sources in the Galactic bulge
- Short Name:
- J/A+A/517/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric catalogue of seven selected fields towards the Galactic bulge, observed with the IRAC and MIPS imaging instruments on-board the Spitzer Space Telescope with unprecedented sensitivity. The locations of the fields are defined in Figure 1 and Table 1 of the paper. In each of the fields, tens of thousands of point sources were detected. The catalogue is split up into seven tables, according to the different fields. Table 5 in the paper gives ten lines of the band-merged catalogue of the Bulge N1 field as an example. In the first paper based on this data set, we present the observations, data reduction, the final catalogue of sources, and a detailed comparison to previous mid-IR surveys of the Galactic bulge, as well as to theoretical isochrones. We find in general good agreement with other surveys and the isochrones, supporting the high quality of our catalogue. Besides a catalogue for each field, fits files of the IRAC and MIPS mosaics are presented, too. As a cautionary note for the users, we would like to add that the least reliable sources in our catalogue are those with detection in only one IRAC band and no MIPS detection, and with (i) either no 2MASS and DENIS counterpart (depending on the field, between 3.1% and 6.7% of the sources), or (ii) a DENIS and 2MASS counterpart at a distance between 1.6 and 3 arcseconds (depending on the field, between 0.4% and 1.0% of the sources).
- ID:
- ivo://CDS.VizieR/J/ApJ/671/323
- Title:
- Spitzer Spectra of a 10mJy galaxy sample
- Short Name:
- J/ApJ/671/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete flux-limited sample of 50 galaxies is presented having f{nu}(24um)>10mJy, chosen from a survey with MIPS on Spitzer of 8.2deg^2^ in the NOAO Deep Wide-Field Survey (NDWFS) region in Bootes. Spectra obtained with the low-resolution modules of IRS on Spitzer are described for 36 galaxies in this sample; 25 show strong PAH emission features characteristic of starbursts, and 11 show silicate absorption or emission, emission lines, or featureless spectra characteristic of AGNs. Infrared or optical spectral classifications are available for 48 of the entire sample of 50; 33 galaxies are classified as starbursts and 15 as AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/663/1149
- Title:
- Spitzer survey of Serpens YSO population
- Short Name:
- J/ApJ/663/1149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the combined IRAC/MIPS c2d Spitzer Legacy observations of the Serpens star-forming region. We describe criteria for isolating bona fide YSOs from the extensive background of extragalactic objects. We then discuss the properties of the resulting high-confidence set of 235 YSOs. An additional 51 lower confidence YSOs outside this area are identified from the MIPS data and 2MASS photometry. We present color-color diagrams to compare our observed source properties with those of theoretical models for star/disk/envelope systems and our own modeling of the objects that are well represented by a stellar photosphere plus circumstellar disk.
- ID:
- ivo://CDS.VizieR/J/AJ/160/130
- Title:
- SpT & NIR color excess of Solar-type stars
- Short Name:
- J/AJ/160/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although solar-analog stars have been studied extensively over the past few decades, most of these studies have focused on visible wavelengths, especially those identifying solar-analog stars to be used as calibration tools for observations. As a result, there is a dearth of well-characterized solar analogs for observations in the near-infrared, a wavelength range important for studying solar system objects. We present 184 stars selected based on solar-like spectral type and V-J and V-K colors whose spectra we have observed in the 0.8-4.2{mu}m range for calibrating our asteroid observations. Each star has been classified into one of three ranks based on spectral resemblance to vetted solar analogs. Of our set of 184 stars, we report 145 as reliable solar-analog stars, 21 as solar analogs usable after spectral corrections with low-order polynomial fitting, and 18 as unsuitable for use as calibration standards owing to spectral shape, variability, or features at low to medium resolution. We conclude that all but five of our candidates are reliable solar analogs in the longer wavelength range from 2.5 to 4.2{mu}m. The average colors of the stars classified as reliable or usable solar analogs are V-J=1.148, V-H=1.418, and V-K= 1.491, with the entire set being distributed fairly uniformly in R.A. across the sky between -27{deg} and +67{deg} in decl.
