EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 460/3 Article
Free access article

Issue A&A
Volume 460, Number 3, December IV 2006
Page(s) 721 - 731
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20064815



A&A 460, 721-731 (2006)
DOI: 10.1051/0004-6361:20064815

SiO and CH $\mathsf{_3}$CCH abundances and dust emission in high-mass star-forming cores

O. Miettinen, J. Harju, L. K. Haikala, and C. Pomrén

Observatory, P.O. Box 14, 00014 University of Helsinki, Finland
    e-mail: osmietti@astro.helsinki.fi

(Received 5 January 2006 / Accepted 5 September 2006)

Abstract
Aims.We determine the fractional SiO abundance in high-mass star-forming cores, and investigate its dependence on physical conditions, to provide constraints on the chemistry models of the formation of SiO in the gas phase or via grain mantle evaporation. The work addresses also CH3CCH chemistry, as the kinetic temperature is determined using this molecule.
Methods.We estimate the physical conditions of 15 high-mass star-forming cores and derive the fractional SiO and CH3CCH abundances using spectral line and dust continuum observations with the SEST.
Results.The kinetic temperatures as derived from CH3CCH range from 25 to 39 K, the average being 33 K. The average gas density in the cores is $4.5 \times 10^6$ cm-3. The SiO emission regions are extended and typically half of the integrated line emission comes from the velocity range traced out by CH3CCH emission. The upper limit of SiO abundance in this "quiescent" gas component is ~10-10. The average CH3CCH abundance is about $7 \times 10^{-9}$. It shows a shallow, positive correlation with the temperature, whereas SiO shows the opposite tendency.
Conclusions.We suggest that the high CH3CCH abundance and its possible increase when the clouds become warmer is related to the intensified desorption of the chemical precursors of the molecule from grain surfaces. In contrast, the observed tendency of SiO does not support the idea that the evaporation of Si-containing species from the grain mantles would be important, and it contradicts models where neutral reactions with activation barriers dominate SiO production. A possible explanation for the decrease is that warmer cores represent more evolved stages of core evolution with fewer high-velocity shocks and thus less efficient SiO replenishment.


Key words: ISM: clouds -- ISM: molecules -- molecular data -- radio continuum: ISM -- radio lines: ISM -- stars: formation



© ESO 2006


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.