http://arxiv.org/abs/1910.05015
We carry out a systematic study of the density structure of gas in the Central Molecular Zone (CMZ) in the Galactic center by extracting clumps from the ATLASGAL 870um survey. We find that the clumps follow a scaling m ~ r ^ 3 which corresponds to a characteristic density of nH2 = 2.5 * 10^3 cm-3 (120 Msun pc^-3) with a variation of 1dex. This characteristic density can be interpreted as the result of pressure equilibrium between the molecular gas and the warm ambient ISM. Different from clumps in the Milky Way disk, self-gravity cannot compress the clumps significantly since strong shear converts gas into pressure-confined droplets which are unable to collapse. The fact that the clumps reach this shear-regulated pressure equilibrium may explain the fact that star formation in the CMZ is highly inefficient compared to the rest of the Milky Way disk. We also identify a population of clumps whose densities are two orders of magnitudes higher in the vicinity of the SgrB2 region, which we argue is produced by the collisions between the clumps. For collisions to occur, processes such as compressive tides probably have created the appropriate condition by assembling the clumps.
G. Li and C. Zhang
Mon, 14 Oct 19
20/69
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