EDP Sciences
Free access
Volume 417, Number 1, April I 2004
Page(s) 115 - 133
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20031733

A&A 417, 115-133 (2004)
DOI: 10.1051/0004-6361:20031733

The circumstellar environments of high-mass protostellar objects

I. Submillimetre continuum emission
S. J. Williams1, G. A. Fuller1 and T. K. Sridharan2

1  Department of Physics, UMIST, PO Box 88, Manchester, M60 1QD, UK
2  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138, USA

(Received 27 March 2003 / Accepted 3 December 2003 )

We present maps of the 850  $\mu$m and 450  $\mu$m continuum emission seen towards a sample of 68 high-mass protostellar candidates with luminosities ranging from 10 $^{2.5}~L_{\odot}$ to ${\sim} 10^{5}$ $L_{\odot}$. Most of these candidate high-mass stars are in the earliest stages of evolution, and have not yet developed an ultra-compact HII region. We observe a variety of continuum emission morphologies, from compact symmetric sources through to multiple cores embedded in long filaments of emission. We find on average there is a 65% probability of an IRAS point-source having a companion detection at submillimetre wavelengths. The ratio of integrated flux to peak flux for our detections shows no strong dependence on distance, suggesting the emission we have observed is primarily from scale-free envelopes with power-law density structures. Assuming a near kinematic distance projection, the clumps we detect vary in mass from ${\sim}1~M_{\odot}$ to over 1000  $M_{\odot}$, with a mean clump mass of 330  $M_{\odot}$, column density of $9\times10^{23}$ cm -2 and diameter of ${\sim}0.6$ pc. The high luminosity and low mass of the smallest clumps suggests they are accompanied by a minimal number of stellar companions, while the most massive clumps may be examples of young protogroups and protoclusters. We measure the spectral index of the dust emission ( $\alpha$) and the spectral index of the dust grain opacity ( $\beta$) towards each object, finding clumps with morphologies suggestive of strong temperature gradients, and of grain growth in their dense inner regions. We find a mean value for $\beta$ of 0.9, significantly smaller than observed towards UCHII regions.

Key words: stars: formation -- stars: circumstellar matter -- ISM: clouds -- ISM: dust, extinction

Offprint request: G. A. Fuller, g.fuller@umist.ac.uk

SIMBAD Objects

© ESO 2004

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.