Spitzer + SMA Observations of an Embedded, Class I Disk in Corona Australis

First Author:
Dawn Peterson
Email: dpeterson AT cfa.harvard.edu
Harvard-Smithsonian CfA
60 Garden St., MS-65
Cambridge, MA 02138 USA
Bourke, Tyler, Harvard-Smithsonian CfA
Jorgensen, Jes, University of Bonn
Allen, Lori, SAO
Gutermuth, Rob, Smith College
Forbrich, Jan, Harvard-Smithsonian CfA
Covey, Kevin, Harvard-Smithsonian CfA

We present high resolution Spitzer and SMA observations of a Class I young stellar object (YSO) in the nearby (150 pc) Corona Australis (CrA) star-forming region. Combined infrared and submillimeter observations provide important complementary information about the distribution of the star-forming material, from the inner envelopes to disks around YSOs. Archival single-dish 850 micron SCUBA maps provide a good estimate of the disk + envelope mass. The SMA, with its excellent angular resolution, can detect the cold outer regions of the disk, and Spitzer is sensitive to the warm inner disk and the star. Taken together, these data allow us to disentangle star from disk, and disk from envelope, the first step toward establishing the evolutionary timescales for the early stages of star formation (Lommen et al. 2008; Jorgensen et al. 2007). We constructed spectral energy distributionsfor YSO candidates in CrA from known J,H,K-band fluxes (2MASS) and Spitzer photometry (3.6-24 micron). Several candidates were observed with the SMA, and one source, IRAS 32 (SMM 8), which displays an extended near-infrared nebula in the infrared, shows a clear CO outflow (and high velocity jet). To first order, the relative contributions of the envelope and disk to the total mass of the protostar can be determined by direct comparison between the single-dish and interferometric continuum data. This explores the relationship between the mid-infrared classification and the evolutionary stage of the protostar in terms of disk and envelope structure -- and can be directly compared to the existing data for the well-studied star forming regions in Ophiuchus and Taurus. For more sophisticated density and temperature structures of the protostellar envelope and disk, we use available 2D dust radiative transfer model tools to reproduce the full SEDs from near-infrared through millimeter wavelengths.
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