Emission of CO, C I, and C II in W3 Main

Abstract

Abstract. We used the KOSMA 3m telescope to map the core 7 × 5 of the Galactic massive star forming region W3 Main in the two fine structure lines of atomic carbon and four mid-J transitions of CO and et al. 1991), this data set allows us to study the physical structure of the molecular cloud interface regions where the occurence of carbon is believed to change from C + to C 0 , and to CO. The molecular gas in W3 Main is warmed by the far ultraviolet (FUV) field created by more than a dozen OB stars. Detailed modelling shows that most of the observed line intensity ratios and absolute intensities are consistent with a clumpy photon dominated region (PDR) of a few hundred unresolved clumps per 0.84 pc beam, filling between 3 and 9% of the volume, with a typical clump radius of 0.025 pc (2.2 ), and typical mass of 0.44 M . The high-excitation lines of CO stem from a 100−200 K layer, as do the [C ] lines. The bulk of the gas mass is however at lower temperatures.

Origin of the prestellar core mass function and link to the IMF – Herschel first results

“…These (sub)millimeter continuum condensations detected from the ground are ∼ 3 orders of magnitude denser than typical CO clumps (e.g. Kramer et al 1998) and feature large ( 50%) mean column density contrasts over their parent background clouds, strongly suggesting they are self-gravitating. The latter is directly confirmed by line observations in a number of cases.…”

“…Core mass functions (histograms with error bars) derived from our Herschel observations of the Polaris (left) and Aquila (right) regions, which reveal of total of 302 starless cores and 541 candidate prestellar cores, respectively Könyves et al 2010). The IMF of single stars (corrected for binaries -e.g., Kroupa 2001), the IMF of multiple systems (e.g., Chabrier 2005), and the typical mass spectrum of CO clumps (e.g., Kramer et al 1998) are shown for comparison. Log-normal fits to the observed CMFs are superimposed.…”

“…A two-segment power-law fit and a log-normal fit are shown for comparison. For reference, the field star IMF (Kroupa 2001), the IMF of multiple systems (Chabrier 2005), and the typical mass spectrum found for CO clumps (Kramer et al 1998) are also shown.…”

“…1-right) is consistent with the Salpeter power-law IMF at the high-mass end (dN/dlogM ∝ M −1.35 ), and significantly steeper than the mass distribution of diffuse CO clumps (dN/dlogM ∝ M −0.7 -e.g. Kramer et al 1998). The difference presumably arises because CO clumps are primarily structured by supersonic turbulence (e.g.…”

A New Comprehensive Catalogue of Infrared Dark Clouds

“…Kramer et al 1998). However, the mass distribution for the fragments within the clouds has a log-normal form, indicative of a turbulent origin for these sub-structures (Hennebelle & Chabrier 2008).…”