Using Spitzer/IRAC observations of a region to be observed by the CoRoT satellite, we have unraveled a new complex star-forming region at low metallicity in the outer Galaxy. We perform a study of S284 in order to outline the chain of events in this star-forming region. We used four-band Spitzer/IRAC photometry as well as Halpha imaging obtained with INT/WFC. Combining these data with the optical photometry obtained in the frame of CoRoTs preparation and the 2MASS catalog we analysed the properties and distribution of young stellar objects (YSOs) associated with point-like sources. We also studied the SEDs of regions of extended emission, complementing our dataset with IRAS and MSX data. We find that S284 is unique in several ways: it is very isolated at the end of a spiral arm and both the diffuse dust and ionized emission are remarkably symmetric. We have partially resolved the central clusters of the three bubbles present in this region. Despite the different scales present in its multiple-bubble morphology, our study points to a very narrow spread of ages among the powering high-mass clusters. In contrast, the particular sawtooth structure of the extended emission at the rim of each ionized bubble harbours either small lower-mass clusters with a younger stellar population or individual young reddened protostars. In particular, triggered star formation is considered to be at work in these regions.
Prior to the launch of JWST, Spitzer/IRAC photometry offers the only means of studying the rest-frame optical properties of z>7 galaxies. Many such high redshift galaxies display a red [3.6] - [4.5] micron colour, often referred to as the "IRAC excess", which has conventionally been interpreted as arising from intense [OIII]+Hbeta emission within the [4.5] micron bandpass. An appealing aspect of this interpretation is similarly intense line emission seen in star-forming galaxies at lower redshift as well as the redshift-dependent behaviour of the IRAC colours beyond z~7 modelled as the various…
We present the Spitzer-IRAC/MIPS Extragalactic survey (SIMES) in the South Ecliptic Pole (SEP) field. The large area covered (7.7 deg$^2$), together with one of the lowest Galactic cirrus emissions in the entire sky and a very extensive coverage by Spitzer, Herschel, Akari, and GALEX, make the SIMES field ideal for extragalactic studies. The elongated geometry of the SIMES area ($\approx$4:1), allowing for a significant cosmic variance reduction, further improves the quality of statistical studies in this field. Here we present the reduction and photometric measurements of the Spitzer/IRAC dat…
We present the $ugriz$-band Dark Energy Camera (DECam) plus 3.6 and 4.5 $μ$m IRAC catalogs for the Spitzer/HETDEX Exploratory Large-Area (SHELA) survey. SHELA covers $\sim24$ deg$^{2}$ of the Sloan Digital Sky Survey (SDSS) Stripe 82 region, with seven bandpasses spanning a wavelength range of 0.35 to 4.5 $μ$m. SHELA falls within the footprint of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), which will provide spectroscopic redshifts for $\sim200{,}000$ Ly$α$ emitters at $1.9<z<3.5$ and also for $\sim200{,}000$ [OII] emitters at $z<0.5$. SHELA's deep, wide-area multiwavelength im…
We present the deepest constraints yet on the median rest-UV+optical SED of $z\sim10$ galaxies, prior to JWST science operations. We constructed stacks based on four robust $J_{125}$-dropouts, previously identified across the GOODS fields. We used archival HST/WFC3 data and the full depth Spitzer/IRAC mosaics from the GREATS program, the deepest coverage at $\sim3-5μ$m to date. The most remarkable feature of the SED is a blue IRAC $[3.6]-[4.5]=-0.18\pm0.25$ mag color. We also find a nearly flat $H_{160}-[3.6]=0.07\pm0.22$ mag color, corresponding to a UV slope $β= -1.92\pm0.25$. This is consis…
We take advantage of new 100-hour Spitzer/IRAC observations available for MACS0647-JD, a strongly lensed $z\approx11$ galaxy candidate, to provide improved constraints on its physical properties. Probing the physical properties of galaxies at $z>8$ is challenging due to the inherent faintness of such sources and the limited wavelength coverage available. Thanks to the high $\approx$2-6$\times$ lensing magnification of the multiple images of MACS0647-JD, we can use the sensitive Spitzer/IRAC data to probe the rest-frame optical fluxes of MACS0647-JD and investigate its physical properties inclu…
We present the first results from an extended survey of the Andromeda galaxy (M31) using 41.1 h of observations by Spitzer-IRAC at 3.6 and 4.5$\,μ$m. This survey extends previous observations to the outer disc and halo, covering total lengths of 4$.\!\!^\circ$4 and 6$.\!\!^\circ$6 along the minor and major axes, respectively. We have produced surface brightness profiles by combining the integrated light from background-corrected maps with stellar counts from a new catalogue of point sources. Using auxiliary catalogues we have carried out a statistical analysis in colour-magnitude space to disc…
We present new stellar mass functions at $z\sim6$, $z\sim7$, $z\sim8$, $z\sim9$ and, for the first time, $z\sim10$, constructed from $\sim800$ Lyman-Break galaxies previously identified over the XDF/UDF, parallels and the five CANDELS fields. Our study is distinctive due to (1) the much deeper ($\sim200$ hour) wide-area Spitzer/IRAC imaging at $3.6μ$m and $4.5μ$m from the GOODS Re-ionization Era wide Area Treasury from Spitzer (GREATS) program and (2) consideration of $z\sim6-10$ sources over a $3\times$ larger area than previous HST+Spitzer studies. The Spitzer/IRAC data enable $\ge2σ$ rest-f…
Measurements of the UV-continuum slopes provide valuable information on the physical properties of galaxies forming in the early universe, probing the dust reddening, age, metal content, and even the escape fraction. While constraints on these slopes generally become more challenging at higher redshifts as the UV continuum shifts out of the Hubble Space Telescope bands (particularly at z>7), such a characterisation actually becomes abruptly easier for galaxies in the redshift window z=9.5-10.5 due to the Spitzer/IRAC 3.6um-band probing the rest-UV continuum and the long wavelength baseline bet…
We present the results from a stellar population modeling analysis of a sample of 162 z=4.5, and 14 z=5.7 Lyman alpha emitting galaxies (LAEs) in the Bootes field, using deep Spitzer/IRAC data at 3.6 and 4.5 um from the Spitzer Lyman Alpha Survey, along with Hubble Space Telescope NICMOS and WFC3 imaging at 1.1 and 1.6 um for a subset of the LAEs. This represents one of the largest samples of high-redshift LAEs imaged with Spitzer IRAC. We find that 30/162 (19%) of the z=4.5 LAEs and 9/14 (64%) of the z=5.7 LAEs are detected at >3-sigma in at least one IRAC band. Individual z=4.5 IRAC-detected…
Recent Spitzer/InfraRed Array Camera (IRAC) photometric observations have revealed that rest-frame optical emission lines contribute signficantly to the broadband fluxes of high-redshift galaxies. Specifically, in the narrow redshift range z~5.1-5.4 the [3.6]-[4.5] color is expected to be very red, due to contamination of the 4.5-micron band by the dominant Halpha line, while the 3.6-micron filter is free of nebular emission lines. We take advantage of new reductions of deep Spitzer/IRAC imaging over the GOODS-North+South fields (Labbe+2015) to obtain a clean measurement of the mean Halpha equ…
Luminous radio sources are thought to lie in galaxy clusters or proto-clusters. The complete sample of 64 high-redshift 3C sources at $1<z<2.5$ has been mapped with the Spitzer Space Telescope. The IRAC $3.6μ$m and $4.5μ$m 5-$σ$ detection limit of $4μ$Jy (22.4 AB mag) allows us to search for the brightest candidate cluster member galaxies associated with the 3C sources. To remove the contamination of foreground stars and galaxies along the lines of sight toward the 3C sources we apply color cuts: removed sources satisfy either the IRAC1/2 cut $[3.6] - [4.5] < -0.3$ or the Pan-STARRS/IRAC cut $…
The infrared data from the Spitzer Space Telescope has provided an invaluable tool for identifying physical processes in star formation. In this study we calculate the IRAC color space of UV fluorescent molecular hydrogen (H$_2$) and Polycyclic Aromatic Hydrocarbon (PAH) emission in photodissociation regions (PDRs) using the Cloudy code with PAH opacities from Draine & Li 2007. We create a set of color diagnostics that can be applied to study the structure of PDRs and to distinguish between FUV excited and shock excited H$_2$ emission. To test this method we apply these diagnostics to Spitzer …
Star-forming regions are often associated with nebulosity. In this study, we investigated infrared diffuse emission in Spitzer IRAC images. The infrared nebula L1527 traces outflows emanating from a low-mass protostar. The nebular color is consistent with the color of a stellar photosphere with large extinction. Nebulae around the HII region W5-East are bright in the infrared. These colors are consistent with the model color of dust containing polycyclic aromatic hydrocarbon (PAH). The strength of ultraviolet irradiation of the nebulae and the small dust fraction were deduced from the infrared…
We present the Spitzer Data Fusion, a database incorporating far-ultraviolet to far-infrared flux measurements as well as photometric and spectroscopic redshifts for 4.4 million IRAC-selected sources detected over 8 extragalactic fields covering 65 deg$^2$ observed by Spitzer in all IRAC and MIPS bands during its cryogenic mission. Deeper Spitzer observations carried out during its warm mission over 5 sub-fields as part of the SERVS project are also presented and analysed in a similar fashion, detecting 2.8 million IRAC-selected sources over 18 deg$^2$ and merging them with multi-wavelength ca…
Effects of diffuse background emission and source crowding on photometric completeness in Spitzer Space Telescope IRAC surveys: The GLIMPSE Catalogs and Archives
We identify 4 unusually bright (H < 25.5) galaxies from HST and Spitzer CANDELS data with probable redshifts z ~ 7-9. These identifications include the brightest-known galaxies to date at z > 7.5. As Y-band observations are not available over the full CANDELS program to perform a standard Lyman-break selection of z > 7 galaxies, we employ an alternate strategy using deep Spitzer/IRAC data. We identify z ~ 7.1 - 9.1 galaxies by selecting z >~ 6 galaxies from the HST CANDELS data that show quite red IRAC [3.6]-[4.5] colors, indicating strong [OIII]+Hbeta lines in the 4.5 micron band. This select…
This paper describes new deep 3.6 and 4.5 micron imaging of three UltraVISTA near-infrared survey stripes within the COSMOS field. The observations were carried out with Spitzer's Infrared Array Camera (IRAC) for the Spitzer Matching Survey of the Ultra-VISTA Deep Stripes (SMUVS). In this work we present our data reduction techniques, and document the resulting mosaics, coverage maps, and catalogs in both IRAC passbands for the three easternmost UltraVISTA survey stripes, covering a combined area of about 0.66 square degrees, of which 0.45 square degrees have at least 20 hr integration time. S…
The Spitzer-Cosmic Assembly Deep Near-Infrared Extragalactic Legacy Survey (S-CANDELS; PI G. Fazio) is a Cycle 8 Exploration Program designed to detect galaxies at very high redshifts (z > 5). To mitigate the effects of cosmic variance and also to take advantage of deep coextensive coverage in multiple bands by the Hubble Space Telescope Multi-Cycle Treasury Program CANDELS, S-CANDELS was carried out within five widely separated extragalactic fields: the UKIDSS Ultra-Deep Survey, the Extended Chandra Deep Field South, COSMOS, the HST Deep Field North, and the Extended Groth Strip. S-CANDELS bu…
We present post-cryogenic Spitzer imaging at 3.6 and 4.5 micron with the Infrared Array Camera (IRAC) of the Spitzer/HETDEX Exploratory Large-Area (SHELA) survey. SHELA covers $\sim$deg$^2$ of the Sloan Digital Sky Survey "Stripe 82" region, and falls within the footprints of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) and the Dark Energy Survey. The HETDEX blind R $\sim$ 800 spectroscopy will produce $\sim$ 200,000 redshifts from the Lyman-$α$ emission for galaxies in the range 1.9 < z < 3.5, and an additional $\sim$200,000 redshifts from the [OII] emission for galaxies at z < …
We present Caltech Submillimeter Observatory CO (2-1) and Spitzer IRAC observations toward IRAS 22506+5944, which is a 10$^4$ $L_{\odot}$ massive star-forming region. The CO (2-1) maps show an east-west bipolar molecular outflow originating from the 3 mm dust continuum peak. The Spitzer IRAC color-composite image reveals a pair of bow-shaped tips which are prominent in excess 4.5 $μ$m emission and are located to the leading fronts of the bipolar outflow, providing compelling evidence for the existence of bow-shocks as the driving agents of the molecular outflow. By comparing our CO (2-1) obser…
We study the stellar population properties of the IRAC-detected $6 \lesssim z \lesssim 10$ galaxy candidates from the Spitzer UltRa Faint SUrvey Program (SURFS UP). Using the Lyman Break selection technique, we find a total of 16 new galaxy candidates at $6 \lesssim z \lesssim 10$ with $S/N \geq 3$ in at least one of the IRAC $3.6μ$m and $4.5μ$m bands. According to the best mass models available for the surveyed galaxy clusters, these IRAC-detected galaxy candidates are magnified by factors of $\sim 1.2$--$5.5$. We find that the IRAC-detected $6 \lesssim z \lesssim 10$ sample is likely not a h…
Interstellar Extinction Law toward the Galactic Center III: J, H, Ks bands in the 2MASS and the MKO systems, and 3.6, 4.5, 5.8, 8.0 micron in the Spitzer/IRAC system
The Spitzer Space Telescope mapped the Perseus molecular cloud complex with IRAC and MIPS as part of the c2d Spitzer Legacy project. This paper combines the observations from both instruments giving an overview of low-mass star formation across Perseus from 3.6 to 70 micron. We provide an updated list of young stellar objects with new classifications and source fluxes from previous works, identifying 369 YSOs in Perseus with the Spitzer dataset. By synthesizing the IRAC and MIPS maps of Perseus and building on the work of previous papers in this series (Jorgensen et al. 2006, Rebull et al. 200…
The Spitzer/IRAC Legacy over the GOODS Fields: Full-Depth 3.6, 4.5, 5.8 and 8.0um Mosaics and Photometry for > 9000 Galaxies at z~3.5-10 from the GOODS Re-ionization Era wide-Area Treasury from Spitzer (GREATS)
We present the first detailed analysis of three extragalactic fields (IRAC Dark Field, ELAIS-N1, ADF-S) observed by the infrared satellite, AKARI, using an optimised data analysis toolkit specifically for the processing of extragalactic point sources. The InfraRed Camera (IRC) on AKARI complements the Spitzer space telescope via its comprehensive coverage between 8-24 microns filling the gap between the Spitzer IRAC and MIPS instruments. Source counts in the AKARI bands at 3.2, 4.1, 7, 11, 15 and 18 microns are presented. At near-infrared wavelengths, our source counts are consistent with coun…
We present ~120,000 Spitzer/IRAC candidate young stellar objects (YSOs) based on surveys of the Galactic midplane between l~255 deg and 110 deg, including the GLIMPSE I, II, and 3D, Vela-Carina, Cygnus X, and SMOG surveys (613 square degrees), augmented by near-infrared catalogs. We employed a classification scheme that uses the flexibility of a tailored statistical learning method and curated YSO datasets to take full advantage of IRAC's spatial resolution and sensitivity in the mid-infrared ~3-9 micron range. Multi-wavelength color/magnitude distributions provide intuition about how the clas…
One of the most challenging aspects of studying galaxies in the z>~7 universe is the infrequent confirmation of their redshifts through spectroscopy, a phenomenon thought to occur from the increasing opacity of the intergalactic medium to Lya photons at z>6.5. The resulting redshift uncertainties inhibit the efficient search for [C II] in z~7 galaxies with sub-mm instruments such as ALMA, given their limited scan speed for faint lines. One means by which to improve the precision of the inferred redshifts is to exploit the potential impact of strong nebular emission lines on the colors of z~4-8…
Spitzer's final Infrared Array Camera (IRAC) observations of SN 1987A show the 3.6 and 4.5 $μ$m emission from the equatorial ring (ER) continues a period of steady decline. Deconvolution of the images reveals that the emission is dominated by the ring, not the ejecta, and is brightest on the west side. Decomposition of the marginally resolved emission also confirms this, and shows that the west side of the ER has been brightening relative to the other portions of the ER. The infrared (IR) morphological changes resemble those seen in both the soft X-ray emission and the optical emission. The in…
We describe the first data release from the Spitzer-IRAC Equatorial Survey (SpIES); a large-area survey of 115 deg^2 in the Equatorial SDSS Stripe 82 field using Spitzer during its 'warm' mission phase. SpIES was designed to probe sufficient volume to perform measurements of quasar clustering and the luminosity function at z > 3 to test various models for "feedback" from active galactic nuclei (AGN). Additionally, the wide range of available multi-wavelength, multi-epoch ancillary data enables SpIES to identify both high-redshift (z > 5) quasars as well as obscured quasars missed by optical su…
We present $Spitzer$ IRAC mid-infrared point source catalogs for mosaics covering the fields of the nearby ($\lesssim$4 Mpc) galaxies NGC 55, NGC 253, NGC 2366, NGC 4214, and NGC 5253. We detect a total of 20159 sources in these five fields. Point spread function photometry was performed on sources detected in both $Spitzer$ IRAC 3.6 $μ$m and 4.5 $μ$m bands at greater than 3$σ$ above background. These data were then supplemented by aperture photometry in the IRAC 5.8 $μ$m and 8.0 $μ$m bands conducted at the positions of the shorter wavelength sources. For sources with no detected object in the…
We present a mid-infrared (IR) sample study of nearby ultraluminous X-ray sources (ULXs) using multi-epoch observations with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. Spitzer/IRAC observations taken after 2014 were obtained as part of the Spitzer Infrared Intensive Transients Survey (SPIRITS). Our sample includes 96 ULXs located within 10 Mpc. Of the 96~ULXs, 12 have candidate counterparts consistent with absolute mid-IR magnitudes of supergiants, and 16 counterparts exceeded the mid-IR brightness of single supergiants and are thus more consistent with star clusters or n…
Using the first epoch of four-band NIRCam observations obtained by the James Webb Space Telescope (JWST) Prime Extragalactic Areas for Reionization and Lensing Science Program in the Spitzer IRAC Dark Field, we search for F150W and F200W dropouts. In 14.2 arcmin^2, we have found eight F150W dropouts and eight F200W dropouts, all brighter than 27.5 mag (the brightest being ~24 mag) in the band to the red side of the break. As they are detected in multiple bands, these must be real objects. Their nature, however, is unclear, and characterizing their properties is important for realizing the full…
The IRAC mapping of the NMBS-II fields program is an imaging survey at 3.6 and 4.5$μ$m with the Spitzer Infrared Array Camera (IRAC). The observations cover three Canada-France-Hawaii Telescope Legacy Survey Deep (CFHTLS-D) fields, including one also imaged by AEGIS, and two MUSYC fields. These are then combined with archival data from all previous programs into deep mosaics. The resulting imaging covers a combined area of about 3 $deg^2$, with at least $\sim$2 hr integration time for each field. In this work, we present our data reduction techniques and document the resulting coverage maps at…
