Universität zu Köln

Peters, Thomas, Girichidis, Philipp ORCID: 0000-0002-9300-9914, Gatto, Andrea, Naab, Thorsten ORCID: 0000-0002-7314-2558, Walch, Stefanie ORCID: 0000-0001-6941-7638, Wuensch, Richard, Glover, Simon C. O., Clark, Paul C., Klessen, Ralf S. and Baczynski, Christian (2015). IMPACT OF SUPERNOVA AND COSMIC-RAY DRIVING ON THE SURFACE BRIGHTNESS OF THE GALACTIC HALO IN SOFT X-RAYS. Astrophys. J. Lett., 813 (2). BRISTOL: IOP PUBLISHING LTD. ISSN 2041-8213

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Abstract

The halo of the Milky Way contains a hot plasma with a surface brightness in soft X-rays of the order 10(-12) erg cm(-2) s(-1) deg(-2). The origin of this gas is unclear, but so far numerical models of galactic star formation have failed to reproduce such a large surface brightness by several orders of magnitude. In this paper, we analyze simulations of the turbulent, magnetized, multi-phase interstellar medium including thermal feedback by supernova explosions as well as cosmic-ray feedback. We include a time-dependent chemical network, self-shielding by gas and dust, and self-gravity. Pure thermal feedback alone is sufficient to produce the observed surface brightness, although it is very sensitive to the supernova rate. Cosmic rays suppress this sensitivity and reduce the surface brightness because they drive cooler outflows. Self-gravity has by far the largest effect because it accumulates the diffuse gas in the disk in dense clumps and filaments, so that supernovae exploding in voids can eject a large amount of hot gas into the halo. This can boost the surface brightness by several orders of magnitude. Although our simulations do not reach a steady state, all simulations produce surface brightness values of the same order of magnitude as the observations, with the exact value depending sensitively on the simulation parameters. We conclude that star formation feedback alone is sufficient to explain the origin of the hot halo gas, but measurements of the surface brightness alone do not provide useful diagnostics for the study of galactic star formation.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Peters, Thomas UNSPECIFIED UNSPECIFIED UNSPECIFIED Girichidis, Philipp UNSPECIFIED orcid.org/0000-0002-9300-9914 UNSPECIFIED Gatto, Andrea UNSPECIFIED UNSPECIFIED UNSPECIFIED Naab, Thorsten UNSPECIFIED orcid.org/0000-0002-7314-2558 UNSPECIFIED Walch, Stefanie UNSPECIFIED orcid.org/0000-0001-6941-7638 UNSPECIFIED Wuensch, Richard UNSPECIFIED UNSPECIFIED UNSPECIFIED Glover, Simon C. O. UNSPECIFIED UNSPECIFIED UNSPECIFIED Clark, Paul C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Klessen, Ralf S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Baczynski, Christian UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-387093
DOI:	10.1088/2041-8205/813/2/L27
Journal or Publication Title:	Astrophys. J. Lett.
Volume:	813
Number:	2
Date:	2015
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	2041-8213
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language XMM-NEWTON SURVEY; INTERSTELLAR-MEDIUM; MOLECULAR CLOUDS; INITIAL CONDITIONS; HOT GAS; DISK; SIMULATIONS; TURBULENT; EMISSION; GALAXIES Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/38709