VLA NH3 observations of regions of massive star formation in protostellar cores

Free access article

Issue		A&A Volume 461, Number 1, January I 2007


Page(s)		197 - 204
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20064797

A&A 461, 197-204 (2007)
DOI: 10.1051/0004-6361:20064797

VLA NH₃ observations of regions of massive star formation in protostellar cores

Y. Wang^{1, 2}, Y. Wu¹, Q. Zhang², R.-Q. Mao³, and M. Miller⁴

¹ Astronomy Department and CAS-PKU Joint Beijing Astrophysics Center, Peking University, Beijing 100871, PR China
e-mail: ywang@cfa.harvard.edu
² Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
³ Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China
⁴ I, Physics Institute, Koln Univ., Zulpicher St., 50937 Koln, Germany

(Received 1 January 2006 / Accepted 20 August 2006)

Abstract
Aims.The high angular resolution images with the Very Large Array (VLA) allow us to explore the general properties of protostellar cores in massive star forming regions at large distances.
Methods.We observed the NH₃ (J, K) = (1, 1) and (2, 2) lines toward five massive protostar candidates (IRAS 18196-1331, IRAS 18352-0148, IRAS 18361-0627, IRAS 18414-0339 and IRAS 19474+2637) with the VLA D configuration.
Results.We found that these objects have hundreds of solar masses in dense gas with rotation temperatures from 8 to 27 K. No 1.3 cm continuum emission was detected at an rms of ~0.7 mJy in all sources except IRAS 18361-0627. We identified 60 clumps and determined their physical parameters (e.g. line width, rotation temperature, size, and mass). The clump masses range from 0.1 $M_\odot$ to 4800 $M_\odot$ . The average size, line width and temperature are 0.1 $\pm$ 0.06 pc, 1.3 $\pm$ 0.4 km s^-1 and 16 $\pm$ 5 K. The discrepancy between NH₃ and (sub)mm continuum emission is found in IRAS 18196-1331. This phenomenon could occur as a result of the NH₃ abundance variation being affected by the UV illumination.

Key words: ISM: clouds -- ISM: kinematics and dynamics -- stars: formation

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.