- 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.
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Search Results
- 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/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/ApJS/228/5
- Title:
- Spitzer photometry of ~1million stars in M31 & 15 gal.
- Short Name:
- J/ApJS/228/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer IRAC 3.6-8{mu}m and Multiband Imaging Photometer 24{mu}m point-source catalogs for M31 and 15 other mostly large, star-forming galaxies at distances ~3.5-14Mpc, including M51, M83, M101, and NGC 6946. These catalogs contain ~1 million sources including ~859000 in M31 and ~116000 in the other galaxies. They were created following the procedures described in Khan et al. (2015, J/ApJS/219/42) through a combination of point-spread function (PSF) fitting and aperture photometry. These data products constitute a resource to improve our understanding of the IR-bright (3.6-24{mu}m) point-source populations in crowded extragalactic stellar fields and to plan observations with the James Webb Space Telescope.
- ID:
- ivo://CDS.VizieR/J/AJ/133/791
- Title:
- Spitzer photometry of normal & interacting galaxies
- Short Name:
- J/AJ/133/791
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer mid-infrared imaging of a sample of 35 tidally distorted premerger interacting galaxy pairs selected from the Arp Atlas. We compare their global mid-infrared properties with those of normal galaxies from the SINGS Spitzer Legacy survey, and separate the disk emission from that of the tidal features. The [8.0um]-[24um], [3.6um]-[24um], and [5.8um]-[8.0um] colors of these optically selected interacting galaxies are redder on average than those of spirals, implying enhancements to the mass-normalized star formation rates (SFRs) of a factor of ~2.
- 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/ApJS/182/628
- Title:
- Spitzer quasar and ULIRG evolution study
- Short Name:
- J/ApJS/182/628
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results from a comprehensive study of 74 ultraluminous infrared galaxies (ULIRGs) and 34 Palomar-Green (PG) quasars within z~0.3 observed with the Spitzer Infrared Spectrograph (IRS). The contribution of nuclear activity to the bolometric luminosity in these systems is quantified using six independent methods that span a range in wavelength and give consistent results within ~+/-10%-15% on average. This agreement suggests that deeply buried active galactic nuclei (AGNs) invisible to Spitzer IRS but bright in the far-infrared are not common in this sample. The average derived AGN contribution in ULIRGs is ~35%-40%, ranging from ~15%-35% among "cool" (f_25_/f_60_<=0.2) optically classified HII-like and LINER ULIRGs to ~50 and ~75% among warm Seyfert 2 and Seyfert 1 ULIRGs, respectively. This number exceeds ~80% in PG QSOs.
- ID:
- ivo://CDS.VizieR/J/A+A/508/117
- Title:
- Spitzer selected starbursts at z~2
- Short Name:
- J/A+A/508/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wide-field Spitzer surveys allow identification of thousands of potentially high-z submillimeter galaxies (SMGs) through their bright 24um emission and their mid-IR colors. We want to determine the average properties of such z~2 Spitzer-selected SMGs by combining millimeter, radio, and infrared photometry for a representative IR-flux (lambda_rest_~8um) limited sample of SMG candidates. A complete sample of 33 sources believed to be starbursts (5.8um-peakers) was selected in the (0.5deg^2^) J1046+56 field with selection criteria F_24um>400uJy, the presence of a redshifted stellar emission peak at 5.8um, and r'_Vega_>23. The field, part of the SWIRE Lockman Hole field, benefits from very deep VLA/GMRT 20cm, 50cm, and 90cm radio data (all 33 sources are detected at 50cm), and deep 160um and 70um Spitzer data. The 33 sources, with photometric redshifts ~1.5-2.5, were observed at 1.2mm with IRAM-30m/MAMBO to an rms ~0.7-0.8mJy in most cases. Their millimeter, radio, 7-band Spitzer, and near-IR properties were jointly analyzed.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/1778
- Title:
- Spitzer sources in SWIRE/XMM/ELAIS-S1 field
- Short Name:
- J/ApJ/703/1778
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of optical spectroscopic identifications of sources detected by Spitzer at 3.6 or 24um down to ~10 and ~280uJy, respectively, in the SWIRE/XMM-Newton/ELAIS-S1 field and classified via line width analysis and diagnostic diagrams. A total of 1376 sources down to R~24.2mag have been identified (1362 detected at 3.6um, 419 at 24um, and 405 at both) by low-resolution optical spectroscopy carried out with FORS2, VIMOS, and EFOSC2 at the Very Large Telescope and 3.6m ESO telescope. The spectroscopic campaigns have been carried out over the central 0.6deg^2^ area of ELAIS-S1 which, in particular, has also been observed by XMM-Newton and Chandra. We find the first direct optical spectroscopic evidence that the fraction of active galactic nuclei (AGNs; mostly AGN2) increases with increasing F(24um)/F(R) ratio, reaching values of 70(+/-20)% in the range 316<F(24um)/F(R)<1000. We present an Infrared Array Camera-Multiband Imaging Photometer color-color diagram able to separate AGN1 from obscured AGN2 candidates. After having corrected for the spectroscopic incompleteness of our sample, the result is that the AGN fraction at F(24um)~0.8mJy is ~22(+/-7)% and decreases slowly to ~19(+/-5)% down to F(24um)~0.3mJy.
- 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).
