A Comparative Study of Giant Molecular Clouds in M51, M33, and the Large Magellanic Cloud
Abstract
We compare the properties of giant molecular clouds (GMCs) in M51 identified by the Plateau de Bure Interferometer Whirlpool Arcsecond Survey with GMCs identified in wide-field, high-resolution surveys of CO emission in M33 and the Large Magellanic Cloud (LMC). We find that GMCs in M51 are larger, brighter, and have higher velocity dispersions relative to their sizes than equivalent structures in M33 and the LMC. These differences imply that there are genuine variations in the average mass surface density \langle \Sigma _H_{2} \rangle of the different GMC populations. To explain this, we propose that the pressure in the interstellar medium surrounding the GMCs plays a role in regulating their density and velocity dispersion. We find no evidence for a correlation between size and linewidth in M51, M33, or the LMC when the CO emission is decomposed into GMCs, although moderately robust correlations are apparent when regions of contiguous CO emission (with no size limitation) are used. Our work demonstrates that observational bias remains an important obstacle to the identification and study of extragalactic GMC populations using CO emission, especially in molecule-rich galactic environments.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2013
- DOI:
- 10.1088/0004-637X/779/1/46
- arXiv:
- arXiv:1309.3453
- Bibcode:
- 2013ApJ...779...46H
- Keywords:
-
- galaxies: individual: M51 M33 Large Magellanic Cloud;
- galaxies: ISM;
- ISM: clouds;
- ISM: molecules;
- ISM: structure;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 25 pages, 11 figures, accepted for publication in ApJ. Uses emulateapj LaTeX macros. For more information on PAWS, further papers and data, see http://www.mpia.de/PAWS/