We present maps of over 1.5 deg2 in Chamaeleon (Cha) II at 24, 70, and 160 μm observed with the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) and a 1.2 deg2 millimeter map from SIMBA on the Swedish-ESO Submillimetre Telescope (SEST). The c2d Spitzer Legacy Team's data reduction pipeline is described in detail. Over 1500 24 μm sources and 41 70 μm sources were detected by MIPS with fluxes greater than 10 σ. More than 40 potential YSOs are identified with a MIPS and 2MASS color-color diagram and by their spectral indices, including two previously unknown sources with 24 μm excesses. Our new SIMBA millimeter map of Cha II shows that only a small fraction of the gas is in compact structures with high column densities. The extended emission seen by MIPS is compared with previous CO observations. Some selected interesting sources, including two detected at 1 mm, associated with Cha II are discussed in detail, and their SEDs are presented. The classification of these sources using MIPS data is found to be consistent with that of previous studies.

Using the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope, we have obtained mid-infrared photometry for 25 and 18 low-mass members of the IC 348 and Chamaeleon I star-forming clusters, respectively (>M6, M ≲ 0.08 M☉). We find that 42% ± 13% and 50% ± 17% of the two samples exhibit excess emission indicative of circumstellar disks. In comparison, the disk fractions for stellar members of these clusters are 33% ± 4% and 45% ± 7% (M0-M6, 0.7 M☉ ≳ M ≳ 0.1 M☉). The similarity in the disk fractions of stars and brown dwarfs is consistent with a common formation mechanism and indicates that the raw materials for planet formation are available around brown dwarfs as often as around stars.

We present an analysis of stellar distributions for the young stellar clusters GGD 12-15, IRAS 20050+2720, and NGC 7129, which range in far-IR luminosity from 227 to 5.68 × 103 L☉ and are all still associated with their natal molecular clouds. The data used for this analysis include near-IR data obtained with FLAMINGOS on the MMT and newly obtained wide-field 850 μm emission maps from SCUBA on the JCMT. Cluster size and azimuthal asymmetry are measured via azimuthal and radial averaging methods, respectively. To quantify the deviation of the distribution of stars from circular symmetry, we define an azimuthal asymmetry parameter, and we investigate the statistical properties of this parameter through Monte Carlo simulations. The distribution of young stars is compared to the morphology of the molecular gas using stellar surface density maps and the 850 μm maps. We find that two of the clusters are not azimuthally symmetric and show a high degree of structure. The GGD 12-15 cluster is elongated and is aligned with newly detected filamentary structure at 850 μm. IRAS 20050+2720 is composed of a chain of three subclusters, in agreement with Chen and coworkers, although our results show that two of the subclusters appear to overlap. Significant 850 μm emission is detected toward two of the subclusters but is not detected toward the central subcluster, suggesting that the dense gas may already be cleared there. In contrast to these two highly embedded subclusters, we find an anticorrelation of the stars and dust in NGC 7129, indicating that much of the parental gas and dust has been dispersed. The NGC 7129 cluster exhibits a higher degree of azimuthal symmetry, a lower stellar surface density, and a larger size than the other two clusters, suggesting that the cluster may be dynamically expanding following the recent dispersal of natal molecular gas. These analyses are further evidence that embedded, forming clusters are often not spherically symmetric structures but can be elongated and clumpy and that these morphologies may reflect the initial structure of the dense molecular gas. Furthermore, this work suggests that gas expulsion by stellar feedback results in significant dynamical evolution within the first 3 Myr of cluster evolution. We estimate peak stellar volume densities and discuss the impact of these densities on the evolution of circumstellar disks and protostellar envelopes.

We present Spitzer Space Telescope infrared photometric time series of the transiting extrasolar planet system TrES-1. The data span a predicted time of secondary eclipse, corresponding to the passage of the planet behind the star. In both bands of our observations, we detect a flux decrement with a timing, amplitude, and duration as predicted by published parameters of the system. This signal represents the first direct detection of (i.e., the observation of photons emitted by) a planet orbiting another star. The observed eclipse depths (in units of relative flux) are 0.00066 ± 0.00013 at 4.5 μm and 0.00225 ± 0.00036 at 8.0 μm. These estimates provide the first observational constraints on models of the thermal emission of hot Jupiters. Assuming that the planet emits as a blackbody, we estimate an effective temperature of Tp = 1060 ± 50 K. Under the additional assumptions that the planet is in thermal equilibrium with the radiation from the star and emits isotropically, we find a Bond albedo of A = 0.31 ± 0.14. This would imply that the planet absorbs the majority of stellar radiation incident upon it, a conclusion of significant impact to atmospheric models of these objects. We also compare our data to a previously published model of the planetary thermal emission, which predicts prominent spectral features in our observational bands due to water and carbon monoxide. This model adequately reproduces the observed planet-to-star flux ratio at 8.0 μm; however, it significantly overpredicts the ratio at 4.5 μm. We also present an estimate of the timing of the secondary eclipse, which we use to place a strong constraint on the expression e cos ω, where e is the orbital eccentricity and ω is the longitude of periastron. The resulting upper limit on e is sufficiently small that we conclude that tidal dissipation is unlikely to provide a significant source of energy interior to the planet.

Using the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope, we have obtained mid-infrared photometry of the least massive known brown dwarf in the Chamaeleon I star-forming region. For this young brown dwarf, OTS 44, we have constructed a spectral energy distribution (SED) from 0.8 to 8 μm by combining the measurements at 3.6, 4.5, 5.8, and 8.0 μm from IRAC with ground-based photometry at I, J, H, and K. The resulting SED for OTS 44 exhibits significant excess emission longward of 3 μm relative to the SED expected from the photosphere of the brown dwarf. We have successfully modeled the source of this excess emission in terms of an irradiated viscous accretion disk with ≲ 10-10 M☉ yr-1. With a spectral type of M9.5 and a mass of ~15MJup, OTS 44 is now the coolest and least massive brown dwarf observed to have a circumstellar disk. These measurements demonstrate that disks exist around brown dwarfs even down to the deuterium-burning mass limit and the approximate upper mass limit of extrasolar planetary companions.

The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 μm. Two nearly adjacent 5.′2 × 5.′2 fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 μm; 4.5 and 8 μm). All four detector arrays in the camera are 256 × 256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.

We present observations of the star formation region NGC 7129 taken with the Multiband Imaging Photometer for Spitzer (MIPS). A significant population of sources, likely pre-main-sequence members of the young stellar cluster, are revealed outside the central photoionization region. Combining Infrared Array Camera (IRAC) and ground-based near-infrared images, we have obtained colors and spectral energy distributions for some 60 objects. The [3.6]-[4.5] versus [8]-[24] color-color plane shows sources clustered at several different loci, which roughly correspond to the archetypal evolutionary sequence Class 0, I, II, and III. We obtain preliminary classifications for 36 objects and find significant numbers of both Class I and II objects. Most of the pre-main-sequence candidates are associated with the densest part of the molecular cloud surrounding the photoionization region, indicating active star formation over a broad area outside the central cluster. We discuss three Class II candidates that exhibit evidence of inner disk clearing, which would be some of the youngest known examples of a transition from accretion to optically thin quiescent disks.

We present the initial results from the Infrared Array Camera (IRAC) imaging survey of planetary nebulae (PNs). The IRAC colors of PNs are red, especially in the 8.0 mum band. Emission in this band is likely due to contributions from two strong H(2) lines and a [Ar III] line in that bandpass. IRAC is sensitive to the emission in the halos as well as in the ionized regions that are optically bright. In NGC 246, we have observed an unexpected ring of emission in the 5.8 and 8.0 mum IRAC bands not seen previously at other wavelengths. In NGC 650 and NGC 3132, the 8.0 mum emission is at larger distances from the central star compared to the optical and other IRAC bands, possibly related to the H(2) emission in that band and the tendency for the molecular material to exist outside of the ionized zones. In the flocculi of the outer halo of NGC 6543, however, this trend is reversed, with the 8.0 mum emission bright on the inner edges of the structures. This may be related to the emission mechanism, where the H(2) is possibly excited in shocks in the NGC 6543 halo, whereas H(2) emission is likely fluorescently excited in the UV fields near the central star.

The Infrared Array Camera (IRAC) shallow survey covers 8.5 deg(2) in the NOAO Deep Wide-Field Survey in Bootes with three or more 30 s exposures per position. An overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided. The survey includes approximate to370,000, 280,000, 38,000, and 34,000 sources brighter than the 5 sigma limits of 6.4, 8.8, 51, and 50 muJy at 3.6, 4.5, 5.8, and 8 mum, respectively, including some with unusual spectral energy distributions.

Sensitive 5-38 μm Spitzer Space Telescope and ground-based 3-5 μm spectra of the embedded low-mass protostars B5 IRS1 and HH 46 IRS show deep ice absorption bands superposed on steeply rising mid-infrared continua. The ices likely originate in the circumstellar envelopes. The CO2 bending mode at 15 μm is a particularly powerful tracer of the ice composition and processing history. Toward these protostars, this band shows little evidence for thermal processing at temperatures above 50 K. Signatures of lower temperature processing are present in the CO and OCN- bands, however. The observed CO2 profile indicates an intimate mixture with H2O, but not necessarily with CH3OH, in contrast to some high-mass protostars. This is consistent with the low CH3OH abundance derived from the ground-based L-band spectra. The CO2 : H2O column density ratios are high in both B5 IRS1 and HH 46 IRS (∼35%). Clearly, the Spitzer spectra are essential for studying ice evolution in low-mass protostellar environments and for eventually determining the relation between interstellar and solar system ices.

We describe the astronomical observation template (AOT) for the Infrared Array Camera (IRAC) on the Spitzer Space Telescope (formerly SIRTF, hereafter Spitzer). Commissioning of the AOTs was carried out in the first three months of the Spitzer mission. Strategies for observing fixed and moving targets are described, along with the performance of the AOT in flight. We also outline the operation of the IRAC data reduction pipeline at the Spitzer Science Center (SSC) and describe residual effects in the data due to electronic and optical anomalies in the instrument.

We compare the infrared colors predicted by theoretical models of protostellar envelopes and protoplanetary disks with initial observations of young stellar objects made with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope (Werner et al. 2004, Fazio et al. 2004). Disk and envelope models characterized by infall and/or accretion rates found in previous studies can quantitatively account for the range of IRAC colors found in four young embedded clusters: S 140, S 171, NGC 7129, and Cep C. The IRAC color-color diagram ([3.6]-[4.5] vs. [5.8]-[8.0]) can be used to help to distinguish between young stars with only disk emission and protostars with circumstellar envelopes.

We report initial results from IRAC observations of four young stellar clusters. These regions are part of a larger Spitzer Space Telescope survey of 31 young stellar groups and clusters within 1 kpc of the Sun. In each of the four clusters, there are between 39 and 85 objects with colors inconsistent with reddened stellar photospheres. We identify these objects as young stars with significant emission from circumstellar dust. Applying an analysis developed in a companion paper, we classify these objects as either pre-main-sequence stars with disks (Class II) or protostellar objects (Class I). These show that the sites of recent star formation are distributed over multiparsec size scales. In two clusters, Cepheus C and S140, we find protostars embedded in filamentary dark clouds seen against diffuse emission in the IRAC bands.

We present the analysis of seven-band (1.2 to 8 mum) ground- and space-based imaging of the NGC 7129 young stellar cluster from FLAMINGOS on MMT, Two Micron All Sky Survey (2MASS), and the Infrared Array Camera (IRAC) on Spitzer. An analysis of the H-[4.5] versus J-H colors reveals 84 objects with circumstellar disks. Of these, 42 are located within the cluster core, a 0.5 pc (100") radius region of enhanced stellar surface density. From a luminosity- and extinction-limited sample of the stars within the cluster core boundary we have determined that 54%+/-14% have circumstellar disks. Finally, we report the detection of several resolved outflows in the IRAC 4.5 mum mosaic.

The Infrared Array Camera (IRAC) on Spitzer Space Telescope includes four Raytheon Vision Systems focal plane arrays, two with InSb detectors, and two with Si:As detectors. A brief comparison of pre- flight laboratory results vs. in-flight performance is given, including quantum efficiency and noise, as well as a discussion of irregular effects, such as residual image performance, "first frame effect", "banding", "column pull-down" and multiplexer bleed. Anomalies not encountered in pre-flight testing, as well as post-flight laboratory tests on these anomalies at the University of Rochester and at NASA Ames using sister parts to the flight arrays, are emphasized.

We present observations of L1014, a dense core in the Cygnus region previously thought to be starless, but data from the Spitzer Space Telescope show the presence of an embedded source. We propose a model for this source that includes a cold core, heated by the interstellar radiation field, and a low-luminosity internal source. The low luminosity of the internal source suggests a substellar object. If L1014 is representative, other "starless" cores may turn out to harbor central sources.

Crucial steps in the formation of stars and planets can be studied only at mid‐ to far‐infrared wavelengths, where the Space Infrared Telescope (SIRTF) provides an unprecedented improvement in sensitivity. We will use all three SIRTF instruments (Infrared Array Camera [IRAC], Multiband Imaging Photometer for SIRTF [MIPS], and Infrared Spectrograph [IRS]) to observe sources that span the evolutionary sequence from molecular cores to protoplanetary disks, encompassing a wide range of cloud masses, stellar masses, and star‐forming environments. In addition to targeting about 150 known compact cores, we will survey with IRAC and MIPS (3.6–70 μm) the entire areas of five of the nearest large molecular clouds for new candidate protostars and substellar objects as faint as 0.001 solar luminosities. We will also observe with IRAC and MIPS about 190 systems likely to be in the early stages of planetary system formation (ages up to about 10 Myr), probing the evolution of the circumstellar dust, the raw material for planetary cores. Candidate planet‐forming disks as small as 0.1 lunar masses will be detectable. Spectroscopy with IRS of new objects found in the surveys and of a select group of known objects will add vital information on the changing chemical and physical conditions in the disks and envelopes. The resulting data products will include catalogs of thousands of previously unknown sources, multiwavelength maps of about 20 deg2 of molecular clouds, photometry of about 190 known young stars, spectra of at least 170 sources, ancillary data from ground‐based telescopes, and new tools for analysis and modeling. These products will constitute the foundations for many follow‐up studies with ground‐based telescopes, as well as with SIRTF itself and other space missions such as SIM, JWST, Herschel, and TPF/Darwin.

As the first step of a multiwavelength investigation into the relationship between young stellar clusters and their environment, we present fully sampled maps in the J = 1 - 0 lines of (CO)-C-13 and (CO)-O-18 and the J = 2 - 1 line of (CO)-O-18 for a selected group of 30 young stellar groups and clusters within 1 kpc of the Sun. This is the first systematic survey of these regions to date. The clusters range in size from several stars to a few hundred stars. Thirty fields ranging in size from 8' x 8' to 30' x 60' were mapped with 47" resolution simultaneously in the two J = 1 - 0 lines at the Five College Radio Astronomy Observatory. Seventeen sources were mapped over fields ranging in size from 3' x 3' to 13' x 13' in the J = 2 - 1 line with 35" resolution at the Submillimeter Telescope Observatory. We compare the cloud properties derived from each of the three tracers in order to better understand systematic uncertainties in determining masses and line widths. Cloud masses are determined independently using the (CO)-C-13 and (CO)-O-18 transitions; these masses range from 30 to 4000 M-.. Finally, we present a simple morphological classification scheme, which may serve as a rough indicator of cloud evolution.

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Space Infrared Telescope Facility (SIRTF). IRAC is a four-channel camera that obtains simultaneous images at 3.6, 4.5, 5.8, and 8 microns. Two adjacent 5.12x5.12 arcmin fields of view in the SIRTF focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. We describe here the results of the instrument functional and calibration tests completed at Ball Aerospace during the integration with the cryogenic telescope assembly, and provide updated estimates of the in-flight sensitivity and performance of IRAC in SIRTF.

We present a catalog of near-infrared photometry of young stars associated with the Ophiuchus molecular cloud based on observations made with the Hubble Space Telescope NICMOS3 camera at 1.1 and 1.6 μm. Our survey covers 0.02 deg2 centered on the dense molecular cores in Lynds 1688. We detect 165 sources at 1.6 μm and 65 sources at 1.1 μm within our estimated completeness limits of 21.0 and 21.5 mag, respectively. An analysis of the cloud extinction, based on existing molecular line maps, suggests that most of the sources lying within the 40 AV extinction contour of the cloud are probable cloud members. Approximately half (58/108) of these sources are previously unpublished.The faint embedded sources revealed by these observations are spatially concentrated in three regions of high stellar space density (N > 104 stars pc-3). While the spatial distribution of these sources reflects that of the brighter, well-known population of young stars in Ophiuchus, it is distinctly different from the distribution of cool concentrations seen in the submillimeter. Seven new brown dwarf candidates are identified based on their infrared colors and their projected locations on high column density regions of the molecular cloud. Eight new candidate binary and five new candidate triple systems, having separations between 0.″2 and 10'' (29-1450 AU) are reported. The spatial resolution and sensitivity of these observations reveal five apparent disk/envelope systems seen via scattered light and four nebulous objects with complex morphologies.