Universität zu Köln

Correia, C., Burkhart, B., Lazarian, A., Ossenkopf, V., Stutzki, J., Kainulainen, J., Kowal, G. and de Medeiros, J. R. (2014). OPACITY BROADENING OF (CO)-C-13 LINEWIDTHS AND ITS EFFECT ON THE VARIANCE-SONIC MACH NUMBER RELATION. Astrophys. J. Lett., 785 (1). BRISTOL: IOP PUBLISHING LTD. ISSN 2041-8213

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Abstract

We study how the estimation of the sonic Mach number (M-s) from (CO)-C-13 linewidths relates to the actual three-dimensional sonic Mach number. For this purpose we analyze MHD simulations that include post-processing to take radiative transfer effects into account. As expected, we find very good agreement between the linewidth estimated sonic Mach number and the actual sonic Mach number of the simulations for optically thin tracers. However, we find that opacity broadening causes M-s to be overestimated by a factor of approximate to 1.16-1.3 when calculated from optically thick (CO)-C-13 lines. We also find that there is a dependence on the magnetic field: super-Alfvenic turbulence shows increased line broadening compared with sub-Alfvenic turbulence for all values of optical depth for supersonic turbulence. Our results have implications for the observationally derived sonic Mach number-density standard deviation (sigma(rho)/<(rho)>) relationship, alpha(2)(rho)/<(rho)> = b(2)M(s)(2) , and the related column density standard deviation (alpha(N)/<(N)>) sonic Mach number relationship. In particular, we find that the parameter b, as an indicator of solenoidal versus compressive driving, will be underestimated as a result of opacity broadening. We compare the sigma(N)/<(N)>-M-s relation derived from synthetic dust extinction maps and (CO)-C-13 linewidths with recent observational studies and find that solenoidally driven MHD turbulence simulations have values of sigma(N/)<(N)> which are lower than real molecular clouds. This may be due to the influence of self-gravity which should be included in simulations of molecular cloud dynamics.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Correia, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Burkhart, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lazarian, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ossenkopf, V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stutzki, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kainulainen, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kowal, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED de Medeiros, J. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-440756
DOI:	10.1088/2041-8205/785/1/L1
Journal or Publication Title:	Astrophys. J. Lett.
Volume:	785
Number:	1
Date:	2014
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	2041-8213
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language DENSITY VARIANCE; POWER SPECTRUM; MAGNETOHYDRODYNAMIC TURBULENCE; INTERSTELLAR TURBULENCE; SUPERSONIC TURBULENCE; GAS; RECONNECTION; EMISSION; CLOUDS; LINES Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/44075