EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 430/ 2 Article

Free access article

Issue A&A
Volume 430, Number 2, February I 2005
Page(s) 549 - 560
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20040437



A&A 430, 549-560 (2005)
DOI: 10.1051/0004-6361:20040437

The interstellar C $\mathsf{^{18}}$O/C $\mathsf{^{17}}$O ratio in the solar neighbourhood: The $\rho$ Ophiuchus cloud

J. G. A. Wouterloot1, 2, J. Brand3 and C. Henkel4

1  Joint Astronomy Centre, 660 N. A'ohoku Place, University Park, 96720 Hilo, Hawaii, USA
    e-mail: j.wouterloot@jach.hawaii.edu
2  Radioastronomisches Institut, Univ. Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
3  Istituto di Radioastronomia, CNR, via Gobetti 101, 40129 Bologna, Italy
4  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

(Received 13 March 2004 / Accepted 15 September 2004)

Abstract
Observations of up to ten carbon monoxide (CO and isotopomers) transitions are presented to study the interstellar C 18O/C 17O ratio towards 21 positions in the nearby ( $d\sim140$ pc) low-mass star forming cloud $\rho$ Oph. A map of the C 18O J=1-0 distribution of parts of the cloud is also shown. An average 12C 18O/ 12C 17O isotopomeric ratio of $4.11 \pm 0.14$, reflecting the 18O/ 17O isotope ratio, is derived from Large Velocity Gradient (LVG) calculations. From LTE column densities we derive a ratio of $4.17\pm0.26$. These calculations also show that the kinetic temperature decreases from about 30 K in the cloud envelope to about 10 K in the cloud cores. This decrease is accompanied by an increase of the average molecular hydrogen density from 10 4 cm -3 to $\ga$10 5 cm -3. Towards some lines of sight C 18O optical depths reach values of order unity.


Key words: ISM: abundances -- ISM: clouds -- ISM: molecules -- Galaxy: abundances -- radio lines: ISM -- ISM: individual objects: rho Oph

SIMBAD Objects



© ESO 2005

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.