Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-12-10
Astronomy and Astrophysics
Astrophysics
18 pages. Accepted for publication in Astronomy & Astrophysics
Scientific paper
10.1051/0004-6361:20066499
We observe 84 candidate young high-mass sources in the rare isotopologues C17O and C18O to investigate whether there is evidence for depletion (freeze-out) towards these objects. Observations of the J=2-1 transitions of C18O and C17O are used to derive the column densities of gas towards the sources and these are compared with those derived from submillimetre continuum observations. The derived fractional abundance suggests that the CO species show a range of degrees of depletion towards the objects. We then use the radiative transfer code RATRAN to model a selection of the sources to confirm that the spread of abundances is not a result of assumptions made when calculating the column densities. We find a range of abundances of C17O that cannot be accounted for by global variations in either the temperature or dust properties and so must reflect source to source variations. The most likely explanation is that different sources show different degrees of depletion of the CO. Comparison of the C17O linewidths of our sources with those of CS presented by other authors reveal a division of the sources into two groups. Sources with a CS linewidth >3 km/s have low abundances of C17O while sources with narrower CS lines have typically higher C17O abundances. We suggest that this represents an evolutionary trend. Depletion towards these objects shows that the gas remains cold and dense for long enough for the trace species to deplete. The range of depletion measured suggests that these objects have lifetimes of 2-4x10^5 years.
Fuller Gary A.
Thomas H. S.
No associations
LandOfFree
The Circumstellar Environment of High-Mass Protostellar Objects: IV. C17O Observations and Depletion does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Circumstellar Environment of High-Mass Protostellar Objects: IV. C17O Observations and Depletion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Circumstellar Environment of High-Mass Protostellar Objects: IV. C17O Observations and Depletion will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-405668