AHerschel-SPIRE survey of the Mon R2 giant molecular cloud: analysis of the gas column density probability density function

Abstract

We present a far-IR survey of the entire Mon R2 GMC with Herschel − SP IRE crosscalibrated with P lanck − HF I data. We fit the SEDs of each pixel with a greybody function and an optimal beta value of 1.8. We find that mid-range column densities obtained from far-IR dust emission and near-IR extinction are consistent. For the entire GMC, we find that the column density histogram, or N-PDF, is lognormal below ∼10 21 cm −2 . Above this value, the distribution takes a power law form with an index of -2.16. We analyze the gas geometry, N-PDF shape, and YSO content of a selection of subregions in the cloud. We find no regions with pure lognormal N-PDFs. The regions with a combination of lognormal and one power law N-PDF have a YSO cluster and a corresponding centrally concentrated gas clump. The regions with a combination of lognormal and two power law N-PDF have significant numbers of typically younger YSOs but no prominent YSO cluster. These regions are composed of an aggregate of closely spaced gas filaments with no concentrated dense gas clump. We find that for our fixed scale regions, the YSO count roughly correlates with the N-PDF power law index. The correlation appears steeper for single power law regions relative to two power law regions with a high column density cut-off, as a greater dense gas mass fraction is achieved in the former. A stronger correlation is found between embedded YSO count and the dense gas mass among our regions.

Molecular Cloud Distances Based on the MWISP CO Survey and Gaia DR2

“…Yan et al (2019) determined distances for 52 molecular clouds (purple), most of which are local and at high Galactic latitudes. In order to make a comparison, we rescaled the plot size of two adjacent molecular clouds, Rosette (1.46 pc) and Mon R2 (0.86 kpc), according to their masses (Williams et al 1995;Pokhrel et al 2016). The 5% systematic error is included in the error bars.…”

“…The sizes of the 11 molecular clouds (red circles) and two adjacent molecular clouds (purple), Rosette (1.46 kpc) and Mon R2 (0.86 kpc), are proportional to their masses. The masses of Rosette (Williams et al 1995) and Mon R2 (Pokhrel et al 2016) molecular clouds are rescaled with updated distances, and are 1.3 × 10 5 and 4.3 × 10 4 M respectively.…”

KFPA Examinations of Young STellar Object Natal Environments (KEYSTONE): Hierarchical Ammonia Structures in Galactic Giant Molecular Clouds

“…Moscadelli et al (2009) surrounded by dense gas clumps with masses of 1 − 65 M and kinetic temperatures of 15 − 30 K. Moreover, recent Herschel dust continuum and C 18 O observations by Rayner et al (2017) showed that the gas and dust in Mon R2 has a distinct hub-spoke geometry, with a central hub of protostars and dense cores that may be fed by several connected filaments. The column density probability distribution function from the Herschel observations also shows two power-law tails, suggesting both turbulent-and gravity-dominated regimes in Mon R2 (Schneider et al 2015;Pokhrel et al 2016).…”

On the star-forming ability of Molecular Clouds

“…Even in the nearby MCs the N-PDFs show a considerable variety; Pokhrel et al (2016) for instance, reported that the power-law tail for some regions in the Mon R2 MC exhibits a break. In such clouds the tail at the high-density end can in fact be fitted with two power-laws.…”