van Kempen, T. A. and Longmore, S. N. and Johnstone, D. and Pillai, T. and Fuente, A. (2012) The Small-Scale Physical Structure and Fragmentation Difference of Two Embedded Intermediate Mass Protostars in Orion. Astrophysical Journal, 751 (2). Art. No. 137. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20120620-163555747
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Intermediate-mass (IM) protostars, the bridge between the very common solar-like protostars and the more massive, but rarer, O and B stars, can only be studied at high physical spatial resolutions in a handful of clouds. In this paper, we present and analyze the continuum results from an observing campaign at the Submillimeter Array (SMA) targeting two well-studied IM protostars in Orion, NGC 2071 and L1641 S3 MMS 1. The extended SMA (eSMA) probes structure at angular resolutions up to 0".2, revealing protostellar disks on scales of ∼200 AU. Continuum flux measurements on these scales indicate that a significant amount of mass, a few tens of M_⊙, is present. Envelope, stellar, and disk masses are derived using compact, extended, and eSMA configurations and compared against spectral energy distribution fitting models. We hypothesize that fragmentation into three components occurred within NGC 2071 at an early time, when the envelopes were less than 10% of their current masses, e.g., <0.5 M. No fragmentation occurred for L1641 S3 MMS 1. For NGC 2071, evidence is given that the bulk of the envelope material currently around each source was accreted after the initial fragmentation. In addition, about 30% of the total core mass is not yet associated to one of the three sources. A global accretion model is favored and a potential accretion history of NGC 2071 is presented. It is shown that the relatively low level of fragmentation in NGC 2071 was stifled compared to the expected fragmentation from a Jeans argument. Similarly, the lack of fragmentation in L1641 S3 MMS 1 is likely due to similar arguments.
|Additional Information:||© 2012 The American Astronomical Society. Received 2011 August 1; accepted 2012 March 14; published 2012 May 16. T.v.K. and S.L. were supported as SMA postdoctoral fellows at the Harvard-Smithsonian Center for Astrophysics (CfA) and are grateful to the Submillimeter Array for funding their research. T.v.K.’s current research is supported by NOVA (Nederlandse Onderzoeksschool Voor Astronomie). T.v.K. is also grateful for the facilities at the Joint ALMA Observatories during his association. D.J. acknowledges the support from an NSERC Discovery Grant. T.P. acknowledges support from the Combined Array for Research in Millimeter-wave Astronomy (CARMA), which is supported by the National Science Foundation through grant AST 05-40399. The anonymous referee is thanked for the critical useful positive read-through of the paper. Mark Gurwell, Ken Young (Taco), and David Wilner of the CfA are thanked for track-sharing eSMA observations on short notice. Taco and Remo Tilanus are thanked for their efforts on the eSMA and assistance with data reduction. We are grateful to the other members in the WISH intermediate mass team (Lars Kristensen, Mike Fich, and Carolyn McCoey in particular) for supplying necessary information on the sources and general discussions. Last but not least, we express our appreciation for the help of Tom Megeath by sharing the reduced Spitzer photometry and images on Orion before publication. Facilities: SMA, Spitzer|
|Subject Keywords:||ISM: kinematics and dynamics; stars: formation; submillimeter: ISM; techniques: interferometric|
|Official Citation:||The Small-scale Physical Structure and Fragmentation Difference of Two Embedded Intermediate-mass Protostars in Orion T. A. van Kempen et al. 2012 ApJ 751 137|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Aucoeur Ngo|
|Deposited On:||21 Jun 2012 14:51|
|Last Modified:||26 Dec 2012 15:21|
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