Schnee, S. and Caselli, P. and Goodman, A. and Arce, H. G. and Ballesteros-Paredes, J. and Kuchibhotla, K. (2007) TMC-1C: An Accreting Starless Core. Astrophysical Journal, 671 (2). pp. 1839-1857. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20091116-132935601
- Published Version
Restricted to Repository administrators only
See Usage Policy.
Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20091116-132935601
We have mapped the starless core TMC-1C in a variety of molecular lines with the IRAM 30 m telescope. High-density tracers show clear signs of self-absorption, and subsonic infall asymmetries are present in N_2H^+(1-0) and DCO^+(2-1) lines. The inward velocity profile in N_2H^+(1-0) is extended over a region about 7000 AU in radius around the dust continuum peak, which is the most extended "infalling" region observed in a starless core with this tracer. The kinetic temperature (~12 K) measured from C^(17)O and C^(18)O suggests that their emission comes from a shell outside the colder interior traced by the millimeter continuum dust. The C^(18)O(2-1) excitation temperature drops from 12 to ≃ 10 K away from the center. This is consistent with a volume density drop of the gas traced by the C^(18)O lines, from ≃ 4 × 10^4 cm^(−3) toward the dust peak to ≃ 6 × 10^3 cm^(−3) at a projected distance from the dust peak of 80" (or 11,000 AU). The column density implied by the gas and dust show similar N_2H^+ and CO depletion factors (f_D ≤ 6). This can be explained with a simple scenario in which: (1) the TMC-1C core is embedded in a relatively dense environment [n(H_2) ≃ 10^4 cm^(−3)], where CO is mostly in the gas phase and the N_2H^+ abundance had time to reach equilibrium values; (2) the surrounding material (rich in CO and N_2H^+) is accreting onto the dense core nucleus; (3) TMC-1C is older than 3 × 10^5 yr, to account for the observed abundance of N_2H^+ across the core (≃ 10^(−10) with respect to H_2); and (4) the core nucleus is either much younger (≃ 10^4 yr) or "undepleted" material from the surrounding envelope has fallen toward it in the past 10,000 yr.
|Additional Information:||© 2007 The American Astronomical Society. Received 2007 March 2; accepted 2007 June 27. Our anonymous referee has provided valuable comments and suggestions which have improved the content and clarity of this paper. We would like to thank Phil Myers, Ramesh Narayan, David Wilner, and Doug Johnstone for their suggestions, assistance, and insights. The James Clerk Maxwell Telescope is operated by the Joint Astronomy Centre on behalf of the Particle Physics and Astronomy Research Council of the United Kingdom, the Netherlands Organisation for Scientific Research, and the National Research Council of Canada. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). This material is based on work supported under a National Science Foundation Graduate Research Fellowship. P. C. acknowledges support from the Italian Ministry of Research and University within a PRIN project.|
|Subject Keywords:||dust, extinction; stars : formation; submillimeter|
|Official Citation:||TMC-1C: An Accreting Starless Core S. Schnee, P. Caselli, A. Goodman, H. G. Arce, J. Ballesteros-Paredes, and K. Kuchibhotla 2007 ApJ 671 1839-1857 doi: 10.1086/521577|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||25 Nov 2009 21:35|
|Last Modified:||26 Dec 2012 11:33|
Repository Staff Only: item control page