EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 417/2 Article
Free access article

Issue A&A
Volume 417, Number 2, April II 2004
Page(s) 615 - 624
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20035608



A&A 417, 615-624 (2004)
DOI: 10.1051/0004-6361:20035608

The association between masers and outflows in massive star forming regions

C. Codella1, A. Lorenzani1, A. T. Gallego2, R. Cesaroni3 and L. Moscadelli4

1  Istituto di Radioastronomia, CNR, Sezione di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy
2  IRAM, Avda Divina Pastora 7, Núcleo Central, 18012 Granada, Spain
3  INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
4  INAF, Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, 09012 Capoterra (Cagliari), Italy

(Received 31 October 2003 / Accepted 5 December 2003 )

Abstract
We report the results of a single-dish survey of molecular outflows towards a homogeneous sample of 136 ultracompact H II regions for which we had previously obtained observations in the methanol 6.7 GHz and water 22.2 GHz maser lines. The line profiles of the 13CO J = 1-0 and 2-1 transitions have been compared to those of the corresponding lines of the C 18O isotopomer to reveal the occurrence of line wings and hence of molecular outflows. We found 53 outflows resulting in an overall detection rate of ~39%. The probability to have an outflow increases to about 50% in regions with maser emission, whereas it is about 25% in those without masers. If we consider just the outflow sources, the chance to find a maser is very high: 74%, without a significant difference between H 2O and CH 3OH. These results strongly confirm from a statistical point of view that both types of masers are closely associated with the evolutionary phase when outflows occur.

The temperatures and optical depths of the molecular cloud hosting the ultracompact H II regions and the comparison between the detection rates suggest a tentative evolutionary scheme for massive star forming regions: the earliest phase is associated with maser emission and with an outflow not yet developed enough to be detected with single-dish observations; then maser emission disappears while the outflow is still present; and finally, only the ultracompact HII  region without masers or outflows is present.


Key words: stars: formation -- radio lines: ISM -- ISM: jets and outflows -- ISM: molecules

Offprint request: C. Codella, codella@arcetri.astro.it

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.