Dense gas in a giant molecular filament - Kölner UniversitätsPublikationsServer

Wang, Y., Beuther, H., Schneider, N., Meidt, S. E., Linz, H., Ragan, S., Zucker, C., Battersby, C., Soler, J. D., Schinnerer, E., Bigiel, F., Colombo, D. and Henning, Th (2020). Dense gas in a giant molecular filament. Astron. Astrophys., 641. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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DOI:10.1051/0004-6361/202037928

Abstract

Context. Recent surveys of the Galactic plane in the dust continuum and CO emission lines reveal that large (greater than or similar to 50 pc) and massive (greater than or similar to 10(5)M(circle dot)) filaments, know as giant molecular filaments (GMFs), may be linked to Galactic dynamics and trace the mid-plane of the gravitational potential in the Milky Way. Yet our physical understanding of GMFs is still poor. Aims. We investigate the dense gas properties of one GMF, with the ultimate goal of connecting these dense gas tracers with star formation processes in the GMF. Methods. We imaged one entire GMF located at l similar to 52-54 degrees longitude, GMF54 (similar to 68 pc long), in the empirical dense gas tracers using the HCN(1-0), HNC(1-0), and HCO+(1-0) lines, and their C-13 isotopologue transitions, as well as the N2H+(1-0) line. We studied the dense gas distribution, the column density probability density functions (N-PDFs), and the line ratios within the GMF. Results. The dense gas molecular transitions follow the extended structure of the filament with area filling factors between 0.06 and 0.28 with respect to (CO)-C-13(1-0). We constructed the N-PDFs of H-2 for each of the dense gas tracers based on their column densities and assumed uniform abundance. The N-PDFs of the dense gas tracers appear curved in log-log representation, and the HCO+ N-PDF has the flattest power-law slope index. Studying the N-PDFs for sub-regions of GMF54, we found an evolutionary trend in the N-PDFs that high-mass star-forming and photon-dominated regions have flatter power-law indices. The integrated intensity ratios of the molecular lines in GMF54 are comparable to those in nearby galaxies. In particular, the N2H+/(CO)-C-13 ratio, which traces the dense gas fraction, has similar values in GMF54 and all nearby galaxies except Ultraluminous Infrared Galaxies. Conclusions. As the largest coherent cold gaseous structure in our Milky Way, GMFs, are outstanding candidates for connecting studies of star formation on Galactic and extragalactic scales. By analyzing a complete map of the dense gas in a GMF we have found that: (1) the dense gas N-PDFs appear flatter in more evolved regions and steeper in younger regions, and (2) its integrated dense gas intensity ratios are similar to those of nearby galaxies.

Item Type:

Journal Article

Creators:

Creators	Email	ORCID	ORCID Put Code
Wang, Y.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Beuther, H.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Schneider, N.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Meidt, S. E.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Linz, H.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Ragan, S.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Zucker, C.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Battersby, C.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Soler, J. D.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Schinnerer, E.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Bigiel, F.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Colombo, D.	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED
Henning, Th	UNSPECIFIED	UNSPECIFIED	UNSPECIFIED