TY - JOUR
T1 - THE LOGNORMAL PROBABILITY DISTRIBUTION FUNCTION of the PERSEUS MOLECULAR CLOUD
T2 - A COMPARISON of HI and DUST
AU - Burkhart, Blakesley
AU - Lee, Min Young
AU - Murray, Claire E.
AU - Stanimirović, Snezana
N1 - Publisher Copyright:
© 2015. The American Astronomical Society. All rights reserved.
PY - 2015/10/1
Y1 - 2015/10/1
N2 - The shape of the probability distribution function (PDF) of molecular clouds is an important ingredient for modern theories of star formation and turbulence. Recently, several studies have pointed out observational difficulties with constraining the low column density (i.e., AV < 1) PDF using dust tracers. In order to constrain the shape and properties of the low column density PDF, we investigate the PDF of multiphase atomic gas in the Perseus molecular cloud using opacity-corrected GALFA-HI data and compare the PDF shape and properties to the total gas PDF and the N(H2) PDF. We find that the shape of the PDF in the atomic medium of Perseus is well described by a lognormal distribution and not by a power-law or bimodal distribution. The peak of the atomic gas PDF in and around Perseus lies at the HIH2 transition column density for this cloud, past which the N(H2) PDF takes on a power-law form. We find that the PDF of the atomic gas is narrow, and at column densities larger than the HI-H2 transition, the HI rapidly depletes, suggesting that the HI PDF may be used to find the HI-H2 transition column density. We also calculate the sonic Mach number of the atomic gas by using HI absorption line data, which yield a median value of Ms = 4.0 for the CNM, while the HI emission PDF, which traces both the WNM and CNM, has a width more consistent with transonic turbulence.
AB - The shape of the probability distribution function (PDF) of molecular clouds is an important ingredient for modern theories of star formation and turbulence. Recently, several studies have pointed out observational difficulties with constraining the low column density (i.e., AV < 1) PDF using dust tracers. In order to constrain the shape and properties of the low column density PDF, we investigate the PDF of multiphase atomic gas in the Perseus molecular cloud using opacity-corrected GALFA-HI data and compare the PDF shape and properties to the total gas PDF and the N(H2) PDF. We find that the shape of the PDF in the atomic medium of Perseus is well described by a lognormal distribution and not by a power-law or bimodal distribution. The peak of the atomic gas PDF in and around Perseus lies at the HIH2 transition column density for this cloud, past which the N(H2) PDF takes on a power-law form. We find that the PDF of the atomic gas is narrow, and at column densities larger than the HI-H2 transition, the HI rapidly depletes, suggesting that the HI PDF may be used to find the HI-H2 transition column density. We also calculate the sonic Mach number of the atomic gas by using HI absorption line data, which yield a median value of Ms = 4.0 for the CNM, while the HI emission PDF, which traces both the WNM and CNM, has a width more consistent with transonic turbulence.
KW - dust extinction
KW - galaxies: star formation
KW - magnetohydrodynamics (MHD)
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U2 - 10.1088/2041-8205/811/2/L28
DO - 10.1088/2041-8205/811/2/L28
M3 - Article
AN - SCOPUS:84945178204
SN - 2041-8205
VL - 811
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L28
ER -