A5014933595- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Astronomy and Astrophysical Research
- Atmospheric Ozone and Climate
- Astronomical Observations and Instrumentation
- Spectroscopy and Laser Applications
- Spacecraft and Cryogenic Technologies
- Gamma-ray bursts and supernovae
- Advanced Combustion Engine Technologies
- Atomic and Molecular Physics
- Medical Imaging Techniques and Applications
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Space Exploration and Technology
- Real-time simulation and control systems
- Geophysics and Sensor Technology
- Blood groups and transfusion
- Atmospheric chemistry and aerosols
- Planetary Science and Exploration
- Radio Astronomy Observations and Technology
University of Maryland, College Park
2008-2017
Columbia University
2011-2017
Center for Astrophysics Harvard & Smithsonian
2002-2011
University of Maryland, Baltimore
2010
Smithsonian Astrophysical Observatory
2006-2009
Harvard University Press
2004-2008
European Southern Observatory
2008
Harvard University
2003-2006
Vanderbilt University
1996-2000
Denison University
2000
(Abridged) The c2d Spitzer Legacy project obtained images and photometry with both IRAC MIPS instruments for five large, nearby molecular clouds. This paper combines information drawn from studies of individual clouds into a combined updated statistical analysis star formation rates efficiencies, numbers lifetimes SED classes, clustering properties. Current efficiencies range 3% to 6%. Taken together, the are producing about 260 solar masses stars per Myr. surface density is more than an...
We investigate the relation between star formation rate (SFR) and gas surface densities in Galactic star-forming regions using a sample of young stellar objects (YSOs) massive dense clumps. Our YSO consists located 20 large molecular clouds from Spitzer cores to disks (c2d) Gould's Belt (GB) surveys. These data allow us probe regime low-mass formation, essentially invisible tracers high-mass used establish extragalactic SFR–gas relations. estimate density (Σgas) extinction (AV) maps SFR...
With the goal to study physical and chemical evolution of ices in solar-mass systems, a spectral survey is conducted sample 41 low luminosity YSOs using 3-38 um Spitzer ground-based spectra. The long-known 6.0 6.85 bands are detected toward all sources, with Class 0-type showing deepest ever observed. In almost sources band deeper than expected from bending mode pure solid H2O. depth shape variations remaining 5-7 absorption indicate that it consists 5 independent components, which, by...
We present the full catalog of Young Stellar Objects (YSOs) identified in 18 molecular clouds surveyed by Spitzer Space Telescope "cores to disks" (c2d) and "Gould Belt" (GB) Legacy surveys. Using standard techniques developed c2d project, we identify 3239 candidate YSOs clouds, 2966 which survive visual inspection form our final Gould Belt. compile extinction corrected SEDs for all calculate tabulate infrared spectral index, bolometric luminosity, temperature each object. find that 326...
We report on the properties of pre-main-sequence objects in Taurus molecular clouds as observed seven mid- and far-infrared bands with Spitzer Space Telescope. There are 215 previously identified members star-forming region our ∼44 deg2 map; these exhibit a range colors that we take to define young stars still surrounded by circumstellar dust (noting ∼20% bona fide no detectable excesses). looked for new survey field similar properties, aided extensive optical, X-ray, ultraviolet imaging,...
We present a large-scale millimeter continuum map of the Ophiuchus molecular cloud. Nearly 11 deg2, including all area in cloud with AV ≥ 3 mag, was mapped at 1.1 mm Bolocam on Caltech Submillimeter Observatory (CSO). By design, also covers region infrared Spitzer Space Telescope. detect 44 definite sources, and few likely sources are seen along filament eastern streamer. The indicates that dense cores very clustered often found filaments within Most round, as measured half-power point, but...
We have completed a 1.1 mm continuum survey of 7.5 deg2 the Perseus Molecular Cloud using Bolocam at Caltech Submillimeter Observatory. This represents largest millimeter or submillimeter map to date. Our covers more than 30,000 31'' (FWHM) resolution elements 1 σ rms 15 mJy beam-1. detect total 122 cores above 5 point-source mass detection limit 0.18 M☉, assuming dust temperature TD = 10 K, 60 which are new detections. The function is consistent with broken power law slope α1 1.3 (0.5 M☉ <...
We present sensitive, high angular resolution molecular line observations of C18O and N2H+ toward the dark globule B68. directly compare these data with near-infrared extinction measurements Alves, Lada, & Lada to derive first evidence for depletion N2H+, by inference N2, in a prestellar cloud. also find widespread throughout centrally condensed core B68 Specifically, we emission peak shell partially surrounding dust extinction. Moreover, peaks inside much larger hole has smaller zone,...
We present a search for all embedded protostars with internal luminosities < 1 solar luminosity in the sample of nearby, low-mass star-forming regions surveyed by Spitzer Space Telescope c2d Legacy Project. The (Lint) source is central and excludes arising from external heating. On average, data are sensitive to Lint > 4E-3 (d/140 pc)^2 luminosities, factor 25 better than sensitivity IRAS such objects. selection criteria used identify candidates examine complementary decide whether...
We present observations of 3.86 sq. deg. the Perseus molecular cloud complex with Spitzer Space Telescope Infrared Array Camera (IRAC). The maps show strong extended emission arising from shocked H2 in outflows region and polycyclic aromatic hydrocarbon features. More than 120,000 sources are extracted toward cloud. Based on their IRAC colors comparison to off-cloud extragalactic fields, we identify 400 candidate young stellar objects. About two thirds these associated clusters IC348...
One of the central goals Spitzer Legacy Project ``From Cores to Disks'' (c2d) is determine frequency circumstellar disks around weak-line T Tauri stars (WTTSs) and study properties evolutionary status these disks. Here we present a census for sample over 230 WTTSs located in c2d IRAC MIPS maps Ophiuchus, Lupus, Perseus Molecular Clouds. We find that ~20% magnitude-limited subsample have IR excesses at wavelengths. These frequencies are ~3-6 times larger than recently found relatively...
We have undertaken an unprecedentedly large 1.1 mm continuum survey of three nearby star-forming clouds using Bolocam at the Caltech Submillimeter Observatory. mapped largest areas in each cloud millimeter or submillimeter wavelengths to date: 7.5 deg2 Perseus (Enoch and coworkers), 10.8 Ophiuchus (Young 1.5 Serpens with a resolution 31'', detecting 122, 44, 35 cores, respectively. Here we report on results compare clouds. Average measured angular core sizes their dependence suggest that...
We discuss the combined IRAC/MIPS c2d Spitzer Legacy observations of Serpens star-forming region. describe criteria for isolating bona fide YSOs from extensive background extragalactic objects. then properties resulting high-confidence set 235 YSOs. An additional 51 lower confidence outside this area are identified MIPS data and 2MASS photometry. present color-color diagrams to compare our observed source with those theoretical models star/disk/envelope systems own modeling objects that well...
We combine the results from several multiplicity surveys of pre-main-sequence stars located in four nearby star-forming regions with Spitzer data three different Legacy Projects. This allows us to construct a sample 349 targets, including 125 binaries, which we use investigate effect companions on evolution circumstellar disks. find that distribution projected separations systems excesses is significantly (P∼ 2.4e-5, according K–S test for binaries less than 400 AU) lacking evidence disk. As...
The relation between ices in the envelopes and disks surrounding YSOs those quiescent interstellar medium is investigated. For a sample of 31 stars behind isolated dense cores, ground-based Spitzer spectra photometry 1-25 um wavelength range are combined. baseline for broad overlapping ice features modeled, using calculated giants, H2O silicates. adopted extinction curve derived empirically. Its high resolution allows separation continuum feature extinction. 13-25 ~50% relative to that at...
We present observations of L1014, a dense core in the Cygnus region previously thought to be starless, but data from Spitzer Space Telescope show presence an embedded source. propose model for this source that includes cold core, heated by interstellar radiation field, and low-luminosity internal The low luminosity suggests substellar object. If L1014 is representative, other "starless" cores may turn out harbor central sources.
We present maps of 0.89 deg2 the Serpens dark cloud at 3.6, 4.5, 5.8, and 8.0 μm observed with Spitzer Space Telescope Infrared Array Camera (IRAC). discuss in detail data processing carried out by c2d team on IRAC data. More than 100,000 compact sources have been extracted, but we confine most our discussion to reliable subset these sources. This includes those that are detected above 7 σ all four bands or two shorter together 2MASS. estimate completeness limits for survey from Monte Carlo...
We present c2d Spitzer/IRAC observations of the Lupus I, III and IV dark clouds discuss them in combination with optical near-infrared MIPS data. With Spitzer data, new sample contains 159 stars, 4 times larger than previous one. It is dominated by low- very-low mass stars it complete down to M $\approx$ 0.1M$_\odot$. find 30-40 % binaries separations between 100 2000 AU no apparent effect disk properties members. A large majority objects are Class II or objects, only 20 (12%) I Flat...
We present Spitzer Space Telescope observations of the "evolved starless core" L1521F that reveal presence a very low luminosity object (L < 0.07 L☉). The object, L1521F-IRS, is directly detected at mid-infrared wavelengths (>5 μm), but only in scattered light shorter infrared wavelengths, showing bipolar nebula oriented east-west probably tracing an outflow cavity. strongly suggests L1521F-IRS embedded core. Thus, similar to recently discovered L1014-IRS and previously known IRAM 04191 its...
We present observations of 10.6 deg2 the Perseus molecular cloud at 24, 70, and 160 μm with Spitzer MIPS. The images show prominent, complex extended emission dominated by illuminating B stars on east side cold filaments west side. Of 3950 point sources identified 24 μm, 1141 have 2MASS counterparts. A quarter these populate regions Ks versus - [24] diagram that are distinct from stellar photospheres background galaxies thus likely to be members infrared excess. Nearly half (46%) excess...
We report the discovery of a nearby, embedded cluster young stellar objects, associated filamentary infrared dark cloud, and 4.5 μm shock emission knots from outflows detected in Spitzer IRAC mid-infrared imaging Serpens-Aquila Rift obtained as part Gould Belt Legacy Survey. also present radial velocity measurements region molecular line observations with Submillimeter Array (SMA) that suggest is comoving Serpens Main 3° to north. therefore assign it same distance, 260 pc. The core new...
Using data from the SCUBA Legacy Catalogue (850 um) and Spitzer Space Telescope (3.6 - 70 um), we explore dense cores in Ophiuchus, Taurus, Perseus, Serpens, Orion molecular clouds. We develop a new method to discriminate submillimeter found by as starless or protostellar, using point source photometry wide field surveys. First, identify infrared sources with red colors associated embedded young stellar objects (YSOs). Second, compare positions of these YSO-candidates our cores. With...
We present Spitzer Space Telescope IRAC and MIPS observations of a 0.85 deg^2 field including the Corona Australis (CrA) star-forming region. At distance 130 pc, CrA is one closest regions known to be actively forming stars, particularly within its embedded association, Coronet. Using data, we identify 51 young stellar objects (YSOs) in which include sources well-studied Coronet cluster as well distributed throughout molecular cloud. Twelve YSOs discussed are new candidates, located Known...
Motivated by the long-standing "luminosity problem" in low-mass star formation whereby protostars are underluminous compared to theoretical expectations, we identify 230 18 molecular clouds observed two Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We compile complete spectral energy distributions, calculate Lbol for each source, and study protostellar luminosity distribution. This distribution extends over three orders magnitude, from 0.01 Lsun - 69 Lsun, has a mean...
We report sensitive, high-resolution molecular-line observations of the dark cloud Barnard 68 obtained with IRAM 30 m telescope. analyze spectral-line C18O (1-0), C32S (2-1), C34S and N2H+ (1-0) in order to investigate kinematics dynamical state cloud. find extremely narrow line widths central regions cloud, ΔV = 0.18 ± 0.01 km s-1 0.15 for C34S, respectively. These lines are consistent thermally broadened profiles measured gas temperature 10.5 K. determine thermal pressure be a factor 4-5...