Rethinking a Mysterious Molecular Cloud

Nia Imara

doi:10.1088/0004-637X/803/1/38

paper

Rethinking a Mysterious Molecular Cloud

arXiv:1503.02542 · doi:10.1088/0004-637X/803/1/38

Abstract

I present high-resolution column density maps of two molecular clouds having strikingly different star formation rates. To better understand the unusual, massive G216-2.5, a molecular cloud with no massive star formation, the distribution of its molecular gas is compared to that of the Rosette Molecular Cloud. Far-infrared data from Herschel are used to derive $N (H_{2})$ maps of each cloud and are combined with $I_{CO}$ data to determine the CO-to-H $_{2}$ ratio, $X_{CO}$ . In addition, the probability distribution functions (PDFs) and cumulative mass fractions of the clouds are compared. For G216-2.5, $< N (H_{2}) >= 7.8 \times 1 0^{20} c m^{- 2}$ and $< X_{CO} >= 2.2 \times 1 0^{20} (K k m s^{- 1})^{- 1}$ ; for the Rosette, $< N (H_{2}) >= 1.8 \times 1 0^{21} c m^{- 2}$ and $< X_{CO} >= 2.8 \times 1 0^{20} (K k m s^{- 1})^{- 1}$ . The PDFs of both clouds are log-normal for extinctions below $\sim 2$ mag and both show departures from log-normality at high extinctions. Although it is the less-massive cloud, the Rosette has a higher fraction of its mass in the form of dense gas and contains $1389 M_{⊙}$ of gas above the so-called extinction threshold for star formation, $A_{V} = 7.3$ mag. The G216-2.5 cloud has $874 M_{⊙}$ of dense gas above this threshold.

Accepted for publication in ApJ. 16 pages, 13 figures. See ApJ for high-resolution figures

Rethinking a Mysterious Molecular Cloud

Abstract

References in corpus (11)