Universität zu Köln

Soler, J. D., Beuther, H., Rugel, M., Wang, Y., Clark, P. C., Glover, S. C. O., Goldsmith, P. F., Heyer, M., Anderson, L. D., Goodman, A., Henning, Th., Kainulainen, J., Klessen, R. S., Longmore, S. N., McClure-Griffiths, N. M., Menten, K. M., Mottram, J. C., Ott, J., Ragan, S. E., Smith, R. J., Urquhart, J. S., Bigiel, F., Hennebelle, P., Roy, N. and Schilke, P. (2019). Histogram of oriented gradients: a technique for the study of molecular cloud formation. Astron. Astrophys., 622. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

We introduce the histogram of oriented gradients (HOG), a tool developed for machine vision that we propose as a new metric for the systematic characterization of spectral line observations of atomic and molecular gas and the study of molecular cloud formation models. In essence, the HOG technique takes as input extended spectral-line observations from two tracers and provides an estimate of their spatial correlation across velocity channels. We characterized HOG using synthetic observations of HI and (CO)-C-13(J = 1 -> 0) emission from numerical simulations of magnetohydrodynamic (MHD) turbulence leading to the formation of molecular gas after the collision of two atomic clouds. We found a significant spatial correlation between the two tracers in velocity channels where v(HI) approximate to v(13CO), almost independent of the orientation of the collision with respect to the line of sight. Subsequently, we used HOG to investigate the spatial correlation of the HI, from The HI/OH/recombination line survey of the inner Milky Way (THOR), and the (CO)-C-13(J = 1 -> 0) emission from the Galactic Ring Survey (GRS), toward the portion of the Galactic plane 33.degrees 75 <= l <= 35.degrees 25 and vertical bar b vertical bar <= 1.degrees 25. We found a significant spatial correlation between the two tracers in extended portions of the studied region. Although some of the regions with high spatial correlation are associated with HI self-absorption (HISA) features, suggesting that it is produced by the cold atomic gas, the correlation is not exclusive to this kind of region. The HOG results derived for the observational data indicate significant differences between individual regions: some show spatial correlation in channels around v(HI) approximate to v(13CO) while others present spatial correlations in velocity channels separated by a few kilometers per second. We associate these velocity offsets to the effect of feedback and to the presence of physical conditions that are not included in the atomic-cloud-collision simulations, such as more general magnetic field configurations, shear, and global gas infall.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Soler, J. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beuther, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Rugel, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wang, Y. UNSPECIFIED UNSPECIFIED UNSPECIFIED Clark, P. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Glover, S. C. O. UNSPECIFIED UNSPECIFIED UNSPECIFIED Goldsmith, P. F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Heyer, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Anderson, L. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Goodman, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Henning, Th. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kainulainen, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Klessen, R. S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Longmore, S. N. UNSPECIFIED UNSPECIFIED UNSPECIFIED McClure-Griffiths, N. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Menten, K. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Mottram, J. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ott, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ragan, S. E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Smith, R. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Urquhart, J. S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bigiel, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hennebelle, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Roy, N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schilke, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-156501
DOI:	10.1051/0004-6361/201834300
Journal or Publication Title:	Astron. Astrophys.
Volume:	622
Date:	2019
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language NARROW SELF-ABSORPTION; COLD H-I; INTERSTELLAR-MEDIUM; COLUMN DENSITIES; DARK CLOUDS; WARM; TRANSITION; EMISSION; GAS; SIMULATIONS Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/15650