Universität zu Köln

Johnston, K. G., Beuther, H., Linz, H., Schmiedeke, A., Ragan, S. E. and Henning, Th. (2014). The dynamics and star-forming potential of the massive Galactic centre cloud G0.253+0.016. Astron. Astrophys., 568. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context The massive infrared dark cloud G0.253+0.016 projected similar to 45 pc from the Galactic centre contains similar to 10(5) M-circle dot of dense gas whilst being mostly devoid of observed star-formation tracers. Aims. Our goals are therefore to scrutinise the physical properties, dynamics and structure of this cloud with reference to its starforming potential. Methods. We have carried out a concerted SMA and IRAM 30 m study of this enigmatic cloud in dust continuum, CO isotopologues, several shock tracing molecules, as well as H2CO to trace the gas temperature. In addition, we include ancillary far-IR and sub mm Herschel and SCUBA data in our analysis. Results. We detect and characterise a total of 36 dust cores within G0.253+0.016 at 1.3 nun and 1,37 MITI. with masses between 25 and approximately 250 M-circle dot, and find that the kinetic temperature of the gas traced by H2CO ratios is >320 K on size scales of similar to 0.15 pc. Analysis of the position velocity diagrams of our observed lines shows broad linewidths and strong shock emission in the south of the cloud, indicating that G0.253+0.016 is colliding with another cloud at g, 70 km s(-1) We confirm via an analysis of the observed dynamics in the Central Molecular Zone that it is an elongated structure, orientated with Sat B2 closer to the Sun than Sgr A*, however out results suggest that the actual geometry may be more complex than an elliptical ring. We find that the column density probability distribution function of G0.253+0.016 derived from SMA and SCUBA dust continuum emission is log normal with no discernible power-law tail, consistent with little star formation, and that its width can be explained in the framework of theory predicting the density structure of clouds created by supersonic, magnetised turbulence. We also present the A-variance spectrum of this region, a proxy for the density power spectrum of the cloud and show it is consistent with that expected for clouds with no current star formation. Finally. we show that even after determining a scaled column density threshold for star formation by incorporating the effects of the increased turbulence in the cloud, we would still expect ten stars with masses >15 M-circle dot to form in 00.253+0.016. If these cannot be accounted for by new radio continuum observations, then further physical aspects may be important, such as the background column density level, which would turn an absolute column density threshold for star formation into a critical over density. Conclusions, We conclude that 00.253+0.016 contains high temperatures and wide spread shocks, displaying evidence of interaction with a nearby cloud which we identify at v(LSR) similar to 70 km s(-1). Our analysis of the structure of the cloud can be well-explained by theory of magnetised turbulence, and is consistent with little or no current star formation. Using 00.253+0.016 as a test-bed of the conditions required for star formation in a different physical environment to that of nearby clouds we also conclude that there is not one column density threshold for star formation, but instead this value is dependant on the local physical conditions.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Johnston, K. G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beuther, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Linz, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schmiedeke, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ragan, S. E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Henning, Th. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-432372
DOI:	10.1051/0004-6361/201423943
Journal or Publication Title:	Astron. Astrophys.
Volume:	568
Date:	2014
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 PROBABILITY-DISTRIBUTION FUNCTIONS; YOUNG STELLAR OBJECTS; FACE-ON VIEW; MOLECULAR CLOUDS; DENSITY VARIANCE; FORMATION RATES; MACH NUMBER; HI-GAL; HERSCHEL; TURBULENCE Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/43237