We present the first results of our program to study a sample of local luminous infrared galaxies (LIRGs, L_IR = 10^11-10^12 L_sun) with the Spitzer infrared spectrograph (IRS). In these proceedings we investigate the behavior of the 9.7 um silicate feature in LIRGs. As opposed to the extreme silicate absorptions observed in ultraluminous infrared galaxies (ULIRGs, L_IR = 10^12-10^13 L_sun), LIRGs exhibit intermediate silicate absorption features, comparable to those of starburst galaxies. We also find that most of the LIRGs have the minima of the [NeIII]/[NeII] ratio located at their nuclei. It is likely that increased densities in the nuclei are responsible for the smaller nuclear ratios. In the nuclei, it is also possible that the most massive stars are either absent, or still embedded in ultracompact HII regions. Finally we discuss the possible contribution of an AGN to the nuclear mid-IR emission of the galaxy, which in general is low in these local LIRGs.
The SAGE-LMC, SAGE-SMC and HERITAGE surveys have mapped the Magellanic Clouds in the infrared using the Spitzer and Herschel Space Telescopes. Over 8.5 million point sources were detected and catalogued in the LMC alone. Staring mode observations using the InfraRed Spectrograph (IRS) on board Spitzer have been obtained for 1,000 positions in the LMC and ~250 in the SMC. From the infrared spectroscopy we have identified the nature of the sources for which spectroscopy is available. These IRS staring mode targets represent an important contribution to the SED of these dwarf galaxies. Here we rep…
Mid-Infrared (IR) silicate dust bands observed in heavily obscured active galactic nuclei (AGNs) include information on the mineralogical properties of silicate dust. We aim to investigate the mineralogical picture of the circumnuclear region of heavily obscured AGNs to reveal obscured AGN activities through the picture. In our previous study Tsuchikawa et al. (2021), we investigated the properties of silicate dust in heavily obscured AGNs focusing on the mineralogical composition and the crystallinity with Spitzer/IRS 5.3-12 micron spectra. In this study, we model the full-range Spitzer/IRS 5…
We present $Spitzer$/IRS mid-infrared spectral maps of the Galactic star-forming region M17 as well as IRSF/SIRIUS Br$γ$ and Nobeyama 45-m/FOREST $^{13}$CO ($J$=1--0) maps. The spectra show prominent features due to polycyclic aromatic hydrocarbons (PAHs) at wavelengths of 6.2, 7.7, 8.6, 11.3, 12.0, 12.7, 13.5, and 14.2 $μ$m. We find that the PAH emission features are bright in the region between the HII region traced by Br$γ$ and the molecular cloud traced by $^{13}$CO, supporting that the PAH emission originates mostly from photo-dissociation regions. Based on the spatially-resolved $Spitzer…
This is the first of a series of papers on the Infrared Database of Extragalactic Observables from Spitzer (IDEOS). In this work we describe the identification of optical counterparts of the infrared sources detected in Spitzer Infrared Spectrograph (IRS) observations, and the acquisition and validation of redshifts. The IDEOS sample includes all the spectra from the Cornell Atlas of Spitzer/IRS Sources (CASSIS) of galaxies beyond the Local Group. Optical counterparts were identified from correlation of the extraction coordinates with the NASA Extragalactic Database (NED). To confirm the optic…
We decompose the observed 7.7 $μ$m polycyclic aromatic hydrocarbon (PAH) emission complexes in a large sample of over 7000 mid-infrared spectra of the interstellar medium (ISM) using spectral cubes observed with the Spitzer/IRS-SL instrument. In order to fit the 7.7 $μ$m PAH emission complex we invoke four Gaussian components which are found to be very stable in terms of their peak positions and widths across all of our spectra, and subsequently define a decomposition with fixed parameters which gives an acceptable fit for all the spectra. We see a strong environmental dependence on the inter-…
We present Spitzer MIPS SED and IRS observations of 14 Galactic Supernova Remnants previously identified in the GLIMPSE survey. We find evidence for SNR/molecular cloud interaction through detection of [OI] emission, ionic lines, and emission from molecular hydrogen. Through black-body fitting of the MIPS SEDs we find the large grains to be warm, 29-66 K. The dust emission is modeled using the DUSTEM code and a three component dust model composed of populations of big grains, very small grains, and polycyclic aromatic hydrocarbons. We find the dust to be moderately heated, typically by 30-100 …
The crystalline silicates features are mainly reflected in infrared bands. The Spitzer Infrared Spectrograph (IRS) collected numerous spectra of various objects and provided a big database to investigate crystalline silicates in a wide range of astronomical environments. We apply the manifold ranking algorithm to perform a systematic search for the spectra with crystalline silicates features in the Spitzer IRS Enhanced Products available. In total, 868 spectra of 790 sources are found to show the features of crystalline silicate. These objects are cross-matched with the SIMBAD database as well…
We have investigated the water abundance in shock-heated molecular gas, making use of $Herschel$ measurements of far-infrared CO and H$_2$O line emissions in combination with $Spitzer$ measurements of mid-IR H$_2$ rotational emissions. We present far-infrared line spectra obtained with $Herschel$'s PACS instrument in range spectroscopy mode towards two positions in the protostellar outflow NGC 2071 and one position each in the supernova remnants W28 and 3C391. These spectra provide unequivocal detections, at one or more positions, of 12 rotational lines of water, 14 rotational lines of CO, 8 r…
A survey of mid-IR gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer "Cores to Disks" (c2d) legacy program. The environment of embedded protostars is complex both in its physical structure (envelopes, outflows, jets, protostellar disks) and the physical processes (accretion, irradiation by UV and/or X-rays, excitation through slow and fast shocks) which take place. A key point is to spatially resolve the emission in the Spitzer-IRS spectra. An optimal e…
We use the IRS on Spitzer to observe the southern part of the reflection nebula NGC 2023, including the Southern Ridge, which is a photodissociation region par excellence excited by HD 37903. Five pure-rotational H2 emission lines are detected and mapped over and around the Southern Ridge in order to compare with predicted level column densities from theoretical PDR models. We find very good agreement between PDR model predictions and emission line intensities and ratios measured with Spitzer, leading us to conclude that grain photoelectric heating sufficiently warms the gas to produce the obs…
We present a sample of resolved galactic HII regions and photodissociation regions (PDRs) observed with the Spitzer infrared spectrograph (IRS) in spectral mapping mode between the wavelengths of 5--15 $μ$m. For each object we have spectral maps at a spatial resolution of $\sim$4" in which we have measured all of the mid-infrared emission and absorption features. These include the PAH emission bands, primarily at 6.2, 7.7, 8.6, 11.2 and 12.7 $μ$m, as well as the spectral emission lines of neon and sulfur and the absorption band caused by silicate dust at around 9.8 $μ$m. In this work we descri…
We provide the basic integrated physical properties of all the galaxies contained in the full CASSIS with available broad-band photometry from UV to 22 $μ$m. We have collected photometric measurements in 14 wavelengths from available public surveys in order to study the SED of each galaxy in CASSIS, thus constructing a final sample of 1,146 galaxies in the redshift range 0<z<2.5. The SEDs are modelled with the CIGALE code which relies on the energy balance between the absorbed stellar and the dust emission while taking into account the possible contribution due to the presence of an AGN. We sp…
We have mapped the superwind/halo region of the nearby starburst galaxy M82 in the mid-infrared with $Spitzer-IRS$. The spectral regions covered include the H$_2 S(1)-S(3)$, [NeII], [NeIII] emission lines and PAH features. We estimate the total warm H$_2$ mass and the kinetic energy of the outflowing warm molecular gas to be between $M_{warm}\sim5-17\times10^6$ M$_{\odot}$ and $E_{K}\sim6-20\times10^{53}$ erg. Using the ratios of the 6.2, 7.7 and 11.3 micron PAH features in the IRS spectra, we are able to estimate the average size and ionization state of the small grains in the superwind. Ther…
We present results from our spectroscopic study, using the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope, designed to identify massive young stellar objects (YSOs) in the Galactic Center (GC). Our sample of 107 YSO candidates was selected based on IRAC colors from the high spatial resolution, high sensitivity Spitzer/IRAC images in the Central Molecular Zone (CMZ), which spans the central ~300 pc region of the Milky Way Galaxy. We obtained IRS spectra over 5um to 35um using both high- and low-resolution IRS modules. We spectroscopically identify massive YSOs by the presence o…
Most of the optically classified low ionisation narrow emission-line regions (LINERs) nuclei host an active galactic nuclei (AGN). However, how they fit into the unified model (UM) of AGN is still an open question. The aims of this work are to study at mid-infrared (mid-IR) (1) the Compton-thick nature of LINERs; and (2) the disappearance of the dusty torus in LINERs predicted from theoretical arguments. We have compiled all the available low spectral resolution mid-IR spectra of LINERs from the IRS/Spitzer (40 LINERs). We have complemented this sample with Spitzer/IRS spectra of PGQSOs, S1s, …
Spitzer/IRS spectra from 5 to 37 um for a complete sample of 31 R Coronae Borealis stars (RCBs) are presented. These spectra are combined with optical and near-infrared photometry of each RCB at maximum light to compile a spectral energy distribution (SED). The SEDs are fitted with blackbody flux distributions and estimates made of the ratio of the infrared flux from circumstellar dust to the flux emitted by the star. Comparisons for 29 of the 31 stars are made with the IRAS fluxes from three decades earlier: Spitzer and IRAS fluxes at 12 um and 25 um are essentially equal for all but a minori…
Using the Infrared Spectrograph on board the Spitzer Space Telescope, we have detected emission in the S(0), S(1), and S(2) pure-rotational (v=0-0) transitions of molecular hydrogen (H2) towards 6 positions in two translucent high Galactic latitude clouds, DCld 300.2-16.9 and LDN 1780. The detection of these lines raises important questions regarding the physical conditions inside low-extinction clouds that are far from ultraviolet radiation sources. The ratio between the S(2) flux and the flux from PAHs at 7.9 microns averages 0.007 for these 6 positions. This is a factor of about 4 higher th…
Heavily obscured active galactic nuclei (AGNs) are known to show deep silicate absorption features in the mid-infrared (IR) wavelength range of 10--20~$μ$m. The detailed profiles of the features reflect the properties of silicate dust, which are likely to include information on AGN activities obscured by large amounts of dust. In order to reveal AGN activities obscured by large amounts of dust, we select 115 mid-IR spectra of heavily obscured AGNs observed by Spitzer/IRS, and systematically analyze the composition of silicate dust by spectral fitting using the 10~$μ$m amorphous and 23~$μ$m cry…
We present Spitzer/IRS spectral mapping observations of the luminous infrared galaxy (LIRG) Arp299 (IC694 + NGC3690) covering the central 45arcsec ~ 9kpc. The integrated mid-IR spectrum of Arp299 is similar to that of local starbursts despite its strongly interacting nature and high infrared luminosity, L_IR ~ 6x10^11 Lsun. This is explained because the star formation (probed by e.g. high [NeIII]15.56micron/[NeII]micron line ratios) is spread across at least 6-8kpc. Moreover, a large fraction of this star formation is taking place in young regions of moderate mid-IR optical depths such as the …
We report on spectra of two positions in the XA region of the Cygnus Loop supernova remnant obtained with the InfraRed Spectrograph on the Spitzer Space Telescope. The spectra span the 10-35 micron wavelength range, which contains a number of collisionally excited forbidden lines. These data are supplemented by optical spectra obtained at the Whipple Observatory and an archival UV spectrum from the International Ultraviolet Explorer. Coverage from the UV through the IR provides tests of shock wave models and tight constraints on model parameters. Only lines from high ionization species are det…
We present results from the Spitzer/IRS spectral mapping observations of 15 local luminous infrared galaxies (LIRGs). In this paper we investigate the spatial variations of the mid-IR emission which includes: fine structure lines, molecular hydrogen lines, polycyclic aromatic features (PAHs), continuum emission and the 9.7um silicate feature. We also compare the nuclear and integrated spectra. We find that the star formation takes place in extended regions (several kpc) as probed by the PAH emission as well as the [NeII] and [NeIII] emissions. The behavior of the integrated PAH emission and 9.…
The MIPSGAL 24 $μ$m Galactic Plane Survey has revealed more than 400 compact-extended objects. Less than 15% of these MIPSGAL bubbles (MBs) are known and identified as evolved stars. We present Spitzer observations of 4 MBs obtained with the InfraRed Spectrograph to determine the origin of the mid-IR emission. We model the mid-IR gas lines and the dust emission to infer physical conditions within the MBs and consequently their nature. Two MBs show a dust-poor spectrum dominated by highly ionized gas lines of [\ion{O}{4}], [\ion{Ne}{3}], [\ion{Ne}{5}], [\ion{S}{3}] and [\ion{S}{4}]. We identify…
We present results on the spectral decomposition of 118 Spitzer Infrared Spectrograph (IRS) spectra from local active galactic nuclei (AGN) 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 s…
We conducted a Spitzer Space Telescope survey of 28 Luminous (11 < log(LIR/L_odot) < 12, LIRGs) and Ultra-Luminous Infrared Galaxies (log(LIR/L_odot) > 12, ULIRGs). Many of these galaxies are found in pairs or associations and are powered by either nuclear activity or starformation (Sanders & Mirabel 1996). Our main goal is to understand the relative importance of starbursts and AGNs in interacting systems. Is the frequency of AGN and starbursts in these interacting galaxies related to their luminosities? What is the importance of the merger stage and the frequency of AGNs? We present our conc…
Several authors have claimed that the less luminous active galactic nuclei (AGN) are not capable of sustaining the dusty torus structure. Thus, a gradual re-sizing of the torus is expected when the AGN luminosity decreases. Our aim is to confront mid-infrared observations of local AGN of different luminosities with this scenario. We decomposed about ~100 IRS/Spitzer spectra of LLAGN and powerful Seyferts in order to decontaminate the torus component from other contributors. We have used the affinity propagation (AP) method to cluster the data into five groups within the sample according to tor…
The 9.7$μ$m interstellar spectral feature, arising from the Si--O stretch of amorphous silicate dust, is the strongest extinction feature in the infrared (IR). In principle, the spectral profile of this feature could allow one to diagnose the mineralogical composition of interstellar silicate material. However, observationally, the 9.7$μ$m interstellar silicate extinction profile is not well determined. Here we utilize the Spitzer/IRS spectra of five early-type (one O- and four B-type) stars and compare them with that of unreddened stars of the same spectral type to probe the interstellar exti…
Aims. High angular resolution N-band imaging is used to discern the torus of active galactic nuclei (AGN) from its environment in order to allow a comparison of its mid-infrared properties to the expectations of the unified scenario for AGN. Methods. We present VLT-VISIR images of 25 low-redshift AGN of different Seyfert types, as well as N-band SEDs of 20 of them. In addition, we compare our results for 19 of them to Spitzer IRS spectra. Results. We find that at a resolution of ~ 0.35", all the nuclei of our observed sources are point-like, except for 2 objects whose extension is likely of in…
We present the results of Spitzer IRS infrared 5-35 micron low-resolution spectroscopic energy diagnostics of ultraluminous infrared galaxies (ULIRGs) at z > 0.15, classified optically as non-Seyferts. Based on the equivalent widths of polycyclic aromatic hydrocarbon emission and the optical depths of silicate dust absorption features, we searched for signatures of intrinsically luminous, but optically elusive, buried AGNs in these optically non-Seyfert ULIRGs. We then combined the results with those of non-Seyfert ULIRGs at z < 0.15 and non-Seyfert galaxies with infrared luminosities L(IR) < …
We present the spectral atlas of sources observed in low resolution with the Infrared Spectrograph on board the Spitzer Space Telescope. More than 11,000 distinct sources were extracted using a dedicated algorithm based on the SMART software with an optimal extraction (AdOpt package). These correspond to all 13,000 low resolution observations of fixed objects (both single source and cluster observations). The pipeline includes image cleaning, individual exposure combination, and background subtraction. A particular attention is given to bad pixel and outlier rejection at the image and spectra …
We present continuous, monochromatic star formation rate (SFR) indicators over the mid-infrared wavelength range of 6-70 micron. We use a sample of 58 star forming galaxies (SFGs) in the Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) at z<0.2, for which there is a rich suite of multi-wavelength photometry and spectroscopy from the ultraviolet through to the infrared. The data from the Spitzer infrared spectrograph (IRS) of these galaxies, which spans 5-40 micron, is anchored to their photometric counterparts. The spectral region between 40-70 micron is interpolated using dust model fits to th…
We present Spitzer/IRS low resolution observations of 11 compact circumstellar bubbles from the MIPSGAL 24 μm Galactic Plane Survey. We find that this set of MIPSGAL bubbles (MBs) is divided into two categories, and that this distinction correlates with the morphologies of the MBs in the mid- IR. The four MBs with central sources in the mid-IR exhibit dust-rich, low excitation spectra, and their 24 μm emission is accounted for by the dust continuum. The seven MBs without central sources in the mid-IR have spectra dominated by high excitation gas lines (e.g., [O IV] 26.0 μm, [Ne V] 14.3 and 24.…
The Spitzer Survey of Stellar Structure in Galaxies (S4G) is a volume, magnitude, and size-limited survey of 2352 nearby galaxies with deep imaging at 3.6 and 4.5um. In this paper we describe our surface photometry pipeline and showcase the associated data products that we have released to the community. We also identify the physical mechanisms leading to different levels of central stellar mass concentration for galaxies with the same total stellar mass. Finally, we derive the local stellar mass-size relation at 3.6um for galaxies of different morphologies. Our radial profiles reach stellar m…
NGC 1097 is a nearby Seyfert 1 galaxy with a bright circumnuclear starburst ring, a strong large-scale bar and an active nucleus. We present a detailed study of the spatial variation of the far infrared (FIR) [CII]158um and [OI]63um lines and mid-infrared H2 emission lines as tracers of gas cooling, and of the polycyclic aromatic hydrocarbon (PAH) bands as tracers of the photoelectric heating, using Herschel-PACS, and Spitzer-IRS infrared spectral maps. We focus on the nucleus and the ring, and two star forming regions (Enuc N and Enuc S). We estimated a photoelectric gas heating efficiency ([…
We report the results of spectroscopic mapping observations carried out toward protostellar outflows in the BHR71, L1157, L1448, NGC 2071, and VLA 1623 molecular regions using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations, covering the 5.2 - 37 micron spectral region, provide detailed maps of the 8 lowest pure rotational lines of molecular hydrogen and of the [SI] 25.25 micron and [FeII] 26.0 micron fine structure lines. The molecular hydrogen lines, believed to account for a large fraction of the radiative cooling from warm molecular gas that has been heat…
The Infrared Spectrograph (IRS) on board the Spitzer Space Telescope observed about 15,000 objects during the cryogenic mission lifetime. Observations provided low-resolution (R~60-127) spectra over ~5-38um and high-resolution (R~600) spectra over ~10-37um. The Cornell Atlas of Spitzer/IRS Sources (CASSIS) was created to provide publishable quality spectra to the community. Low-resolution spectra have been available in CASSIS since 2011, and we present here the addition of the high-resolution spectra. The high-resolution observations represent approximately one third of all staring observation…
The center of the Milky Way contains stellar populations spanning a range in age and metallicity, with a recent star formation burst producing young and massive stars. Chemical abundances in the most luminous stellar member of the Nuclear Star Cluster (NSC), IRS 7, are presented for $^{19}$F, $^{12}$C, $^{13}$C, $^{14}$N, $^{16}$O, $^{17}$O, and Fe from an LTE analysis based on spherical modeling and radiative transfer with a 25M$_{\odot}$ model atmosphere, whose chemistry was tailored to the derived photospheric abundances. We find IRS 7 to be depleted heavily in both $^{12}$C (~-0.8 dex) and…
The mid-far-infrared spectral energy distributions (SEDs) of 83 active galaxies, mostly Seyfert galaxies, selected from the extended 12 micron sample are presented. The data were collected using all three instruments, IRAC, IRS, and MIPS, aboard the Spitzer Space Telescope. The IRS data were obtained in spectral mapping mode, and the photometric data from IRAC and IRS were extracted from matched, 20 arcsec diameter circular apertures. The MIPS data were obtained in SED mode, providing very low resolution spectroscopy (R ~ 20) between ~ 55 and 90 microns in a larger, 20 by 30 arcsec synthetic a…
The recent literature suggests that an evolutionary dichotomy exists for early-type galaxies (Es and S0s, ETGs) whereby their central photometric structure (cuspy versus core central luminosity profiles), and figure of rotation (fast (FR) vs. slow (SR) rotators), are determined by whether they formed by "wet" or "dry" mergers. We consider whether the mid infrared (MIR) properties of ETGs, with their sensitivity to accretion processes in particular in the last few Gyr (on average z < 0.2), can put further constraints on this picture. We investigate a sample of 49 ETGs for which nuclear MIR prop…
With Spitzer IRS we have obtained sensitive low-resolution spectroscopy from 5 to 35 microns for six supernova remnants (SNRs) that show evidence of shocked molecular gas: Kes 69, 3C 396, Kes 17, G346.6-0.2, G348.5-0.0 and G349.7+0.2. Bright, pure-rotational lines of molecular hydrogen are detected at the shock front in all remnants, indicative of radiative cooling from shocks interacting with dense clouds. We find the excitation of H2 S(0)-S(7) lines in these SNRs requires two non-dissociative shock components: a slow, 10 km/s C- shock through clumps of density 10^6 cm^-3, and a faster, 40-70…
The galaxy SDSSJ0952+2143 showed remarkable emission-line properties first reported in 2008 (paper I), which are the consequence of a powerful high-energy flare. Here we report follow-up observations of SDSSJ0952+2143, and discuss outburst scenarios in terms of stellar tidal disruption by a SMBH, peculiar variability of an AGN, and a supernova explosion. The optical spectrum of SDSSJ0952+2143 exhibits several peculiarities: an exceptional ratio of [FeVII] transitions over [OIII], a dramatic decrease by a factor of 10 of the highest-ionization lines, a very unusual and variable Balmer line prof…
The Infrared Spectrograph (IRS) on the {\em Spitzer Space Telescope} observed nearly 800 point sources in the Large Magellanic Cloud (LMC), taking over 1,000 spectra. 197 of these targets were observed as part of the Sage-Spec Spitzer Legacy program; the remainder are from a variety of different calibration, guaranteed time and open time projects. We classify these point sources into types according to their infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership, and variability information, using a decision-tree classification m…
