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  1. OA@INAF
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  3. 1 CONTRIBUTI IN RIVISTE (Journal articles)
  4. 1.01 Articoli in rivista
Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/28323
Title: Probability Distribution Function of Gas Surface Density in M33
Authors: CORBELLI, Edvige 
Elmegreen, Bruce G.
Braine, Jonathan
Thilker, David
Issue Date: 2018
Journal: ASTRONOMY & ASTROPHYSICS 
Number: 617
First Page: A125
Abstract: The probability distribution functions (PDFs) for atomic, molecular, and total gas surface densities of M33 are determined at a resolution of about 50~pc over regions that share coherent morphological properties to unveil fingerprints of self-gravity across the star-forming disk. Most of the total gas PDFs from the central region to the edge of the star-forming disk are well-fitted by log-normal functions whose width decreases radially outwards. Because the HI velocity dispersion is approximately constant across the disk, the decrease of the PDF width is consistent with a lower Mach number for the turbulent ISM at large galactocentric radii where a higher fraction of HI is in the warm phase. The atomic gas is found mostly at face-on column densities below N$_{H}^{lim}$=2.5 10$^{21}$~cm$^{-2}$, with small radial variations of N$_{H}^{lim}$. The molecular gas PDFs do not show strong deviations from log-normal functions in the central region where molecular fractions are high. Here the high pressure and rate of star formation shapes the PDF as a log-normal function dispersing self-gravitating complexes with intense feedback at all column densities that are spatially resolved. Power law PDFs for the molecules are found near and above N$_H^{lim}$, in the well defined southern spiral arm and in a continuous dense filament extending at larger galactocentric radii; this is evident in cloud samples at different evolutionary stages along the star formation cycle. In the filament nearly half of the molecular gas departs from a log-normal PDF and power laws are also observed in pre-star forming molecular complexes. The slope of the power law is between -1 and -2. This slope, combined with maps showing where the different parts of the power law PDFs come from, suggest a power-law stratification of density within molecular cloud complexes, which is consistent with the dominance of self-gravity.
URI: http://hdl.handle.net/20.500.12386/28323
URL: http://arxiv.org/abs/1807.00166v1
https://www.aanda.org/articles/aa/abs/2018/09/aa33266-18/aa33266-18.html
ISSN: 0004-6361
DOI: 10.1051/0004-6361/201833266
Bibcode ADS: 2018A&A...617A.125C
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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