The CI lines as tracers of molecular gas, and their prospects at high redshifts

Details The CI lines as tracers of molecular gas, and their prospects at high redshifts The CI lines as tracers of molecular gas, and their prospects at high redshifts

2004-03-03

arxiv.org/abs/astro-ph/0403092v1

Mon.Not.Roy.Astron.Soc. 351 (2004) 147

Astronomy and Astrophysics

Astrophysics

Accepted for publication at the Monthly Notices of the Royal Astronomical Society (29 pages, 5 figures)

Scientific paper

10.1111/j.1365-2966.2004.07762.x

We examine the fine structure lines $^{3}P_{1}\to $$^{3}P_{0}$ (492 GHz) and $ ^{3}P_2\to $$^{3}P_1$ (809 GHz) of neutral atomic carbon as bulk molecular gas mass tracers and find that they can be good and on many occasions better than $ ^{12}$CO transitions, especially at high redshifts. The notion of CI emission as an H$_2$ gas mass tracer challenges the long-held view of its distribution over only a relatively narrow layer in the CII/CI/CO transition zone in FUV-illuminated molecular clouds. Past observations have indeed consistently pointed towards a more extended CI distribution but it was only recently, with the advent of large scale imaging of its $^{3}P_{1}\to $$^{3}P_{0}$ transition, that its surprising ubiquity in molecular clouds has been fully revealed. In the present work we show that under {\it typical} ISM conditions such an ubiquity is inevitable because of well known dynamic and non-equilibrium chemistry processes maintaining a significant [C]/[$ ^{12}$CO] abundance throughout Giant Molecular Clouds during their lifetime. These processes are more intense in star-forming environments where a larger ambient cosmic ray flux will also play an important role in boosting [C]/[$ ^{12}$CO]. The resulting CI lines can be bright and effective H$_2$ mass tracers especially for diffuse ($\sim 10^2-10^3\rm cm^{-3}$) gas while in UV-intense and/or metal-poor environments their H$_2$-tracing capability diminishes because of large scale CII production but nevertheless remains superior to that of $ ^{12}$CO. The best place to take full advantage of CI's capacity to trace H$_2$ is not in the low-$z$ Universe, where large atmospheric absorption at 492 and 809 GHz precludes routine observations, but at high redshifts ($\rm z\ga 1$).

Affiliated with

Also associated with

No associations

Rating

The CI lines as tracers of molecular gas, and their prospects at high redshifts 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 CI lines as tracers of molecular gas, and their prospects at high redshifts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The CI lines as tracers of molecular gas, and their prospects at high redshifts will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-335000