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1091. Spitzer/IRS spectral decompositon of AGN
ID:
ivo://CDS.VizieR/J/ApJ/803/109
Title:
Spitzer/IRS spectral decompositon of AGN
Short Name:
J/ApJ/803/109
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results on the spectral decomposition of 118 Spitzer Infrared Spectrograph (IRS) spectra from local active galactic nuclei (AGNs) using a large set of Spitzer/IRS spectra as templates. The templates are themselves IRS spectra from extreme cases where a single physical component (stellar, interstellar, or AGN) completely dominates the integrated mid-infrared emission. We show that a linear combination of one template for each physical component reproduces the observed IRS spectra of AGN hosts with unprecedented fidelity for a template fitting method with no need to model extinction separately. We use full probability distribution functions to estimate expectation values and uncertainties for observables, and find that the decomposition results are robust against degeneracies. Furthermore, we compare the AGN spectra derived from the spectral decomposition with sub-arcsecond resolution nuclear photometry and spectroscopy from ground-based observations. We find that the AGN component derived from the decomposition closely matches the nuclear spectrum with a 1{sigma} dispersion of 0.12dex in luminosity and typical uncertainties of ~0.19 in the spectral index and ~0.1 in the silicate strength. We conclude that the emission from the host galaxy can be reliably removed from the IRS spectra of AGNs. This allows for unbiased studies of the AGN emission in intermediate- and high-redshift galaxies--currently inaccesible to ground-based observations--with archival Spitzer/IRS data and in the future with the Mid-InfraRed Instrument of the James Webb Space Telescope.
1092. Spitzer/IRS spectra of GOALS luminous IR galaxies
ID:
ivo://CDS.VizieR/J/ApJ/777/156
Title:
Spitzer/IRS spectra of GOALS luminous IR galaxies
Short Name:
J/ApJ/777/156
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the data and our analysis of mid-infrared atomic fine-structure emission lines detected in Spitzer/Infrared Spectrograph high-resolution spectra of 202 local Luminous Infrared Galaxies (LIRGs) observed as part of the Great Observatories All-sky LIRG Survey (GOALS). We readily detect emission lines of [SIV], [NeII], [NeV], [NeIII], [SIII]_18.7{mu}m_, [OIV], [FeII], [SIII]_33.5{mu}m_, and [SiII]. More than 75% of these galaxies are classified as starburst-dominated sources in the mid-infrared, based on the [NeV]/[NeII] line flux ratios and equivalent width of the 6.2{mu}m polycyclic aromatic hydrocarbon feature. We compare ratios of the emission-line fluxes to those predicted from stellar photo-ionization and shock-ionization models to constrain the physical and chemical properties of the gas in the starburst LIRG nuclei. Comparing the [SIV]/[NeII] and [NeIII]/[NeII] line ratios to the Starburst99-Mappings III models with an instantaneous burst history, the emission-line ratios suggest that the nuclear starbursts in our LIRGs have ages of 1-4.5 Myr, metallicities of 1-2Z_{sun}_, and ionization parameters of 2-8x10^7^cm/s. Based on the [SIII]_33.5{mu}m_/[SIII]_18.7{mu}m_ ratios, the electron density in LIRG nuclei is typically one to a few hundred/cm3, with a median electron density of ~300/cm3, for those sources above the low density limit for these lines.
1093. Spitzer mid-IR spectra of 3 molecular clouds
ID:
ivo://CDS.VizieR/J/A+A/469/575
Title:
Spitzer mid-IR spectra of 3 molecular clouds
Short Name:
J/A+A/469/575
Date:
21 Oct 2021
Publisher:
CDS
Description:
This work was conducted as part of the SPECPDR program, dedicated to the study of very small particles and astrochemistry, in Photo-Dissociation Regions (PDRs). We present the analysis of the mid-IR spectro-imagery observations of Ced 201, NCG 7023 East and North-West and rho Ophiuchi West filament. Using the data from all four modules of the InfraRed Spectrograph onboard the Spitzer Space Telescope, we produced a spectral cube ranging from 5 to 35{mu}m, for each one of the observed PDRs. The resulting cubes were analysed using Blind Signal Separation methods (NMF and FastICA).
1094. Spitzer 24{mu}m photometry of A dwarfs
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.
1095. Spitzer observations of pre-main-sequence stars
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.
1096. Spitzer observations of radio-loud AGNs (CARLA)
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.
1097. Spitzer observations of sigma Orionis
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.
1098. Spitzer obs. of warm dust in 83 debris disks
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.
1099. Spitzer photometry of the Trifid nebula (M20)
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.
1100. Spitzer sources in the Galactic bulge
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).