Jørgensen, J. K. and Hogerheijde, M. R. and van Dishoeck, E. F. and Blake, G. A. and Schöier, F. L. (2004) The structure of the NGC 1333-IRAS2 protostellar system on 500 AU scales - An infalling envelope, a circumstellar disk, multiple outflows, and chemistry. Astronomy and Astrophysics, 413 (3). pp. 993-1007. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20120918-115217250
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This paper investigates small-scale (500 AU) structures of dense gas and dust around the low-mass protostellar binary NGC 1333-IRAS2 using millimeter-wavelength aperture-synthesis observations from the Owens Valley and Berkeley-Illinois-Maryland-Association interferometers. The detected λ=3 mm continuum emission from cold dust is consistent with models of the envelope around IRAS2A , based on previously reported submillimeter-continuum images, down to the 3", or 500 AU, resolution of the interferometer data. Our data constrain the contribution of an unresolved point source to 22 mJy. The importance of different parameters, such as the size of an inner cavity and impact of the interstellar radiation field, is tested. Within the accuracy of the parameters describing the envelope model, the point source flux has an uncertainty by up to 25%. We interpret this point source as a cold disk of mass ≳0.3 M_⊙. The same envelope model also reproduces aperture-synthesis line observations of the optically thin isotopic species C^(34)S and H^(13)CO^+. The more optically thick main isotope lines show a variety of components in the protostellar environment: N_(2)H^+ is closely correlated with dust concentrations as seen at submillimeter wavelengths and is particularly strong toward the starless core IRAS2C . We hypothesize that N_(2)H^+ is destroyed through reactions with CO that is released from icy grains near the protostellar sources IRAS2A and B. CS, HCO^+, and HCN have complex line shapes apparently affected by both outflow and infall. In addition to the east-west jet seen in SiO and CO originating from IRAS2A, a north-south velocity gradient near this source indicates a second, perpendicular outflow. This suggests the presence of a binary companion within 0."3 (65 AU) from IRAS2A as driving source of this outflow. Alternative explanations of the velocity gradient, such as rotation in a circumstellar envelope or a single, wide-angle ( $90^\circ$) outflow are less likely.
|Additional Information:||© 2004 ESO. Published by EDP Sciences. Received 18 June 2003; accepted 1 October 2003. The authors thank Kees Dullemond for use of the CGPLUS program and discussions of disk models. The research of J.K.J. is funded by the Netherlands Research School for Astronomy (NOVA) through a network 2 Ph.D. stipend and research in astrochemistry in Leiden is supported by a Spinoza grant. This paper made use of data from a range of telescopes among them the Owens Valley Radio Observatory and Berkeley-Illinois-Maryland-Association millimeter arrays, Onsala Space Observatory 20 m telescope and the James Clerk Maxwell Telescope. The authors are grateful to the staff at all these facilities and their host institutions for technical support, discussions, and hospitality during numerous visits.|
|Subject Keywords:||ISM: individual objects: NGC 1333-IRAS2; stars: formation; ISM: molecules; ISM: jets and outflows|
|Official Citation:||The structure of the NGC 1333-IRAS2 protostellar system on 500 AU scales - An infalling envelope, a circumstellar disk, multiple outflows, and chemistry J. K. Jørgensen, M. R. Hogerheijde, E. F. van Dishoeck, G. A. Blake and F. L. Schöier A&A 413 (3) 993-1007 (2004) DOI: http://dx.doi.org/10.1051/0004-6361:20031550|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||18 Sep 2012 23:11|
|Last Modified:||26 Dec 2012 16:12|
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