Universität zu Köln

Girichidis, Philipp, Naab, Thorsten ORCID: 0000-0002-7314-2558, Hanasz, Michal ORCID: 0000-0002-2370-5631 and Walch, Stefanie (2018). Cooler and smoother - the impact of cosmic rays on the phase structure of galactic outflows. Mon. Not. Roy. Astron. Soc., 479 (3). S. 3042 - 3068. OXFORD: OXFORD UNIV PRESS. ISSN 1365-2966

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Abstract

We investigate the impact of cosmic rays (CRs) on galactic outflows from a multiphase interstellar medium with solar neighbourhood conditions. The three-dimensional magneto-hydrodynamical simulations include CRs as a relativistic fluid in the advection-diffusion approximation. The thermal and chemical state of the interstellar medium is computed with a non-equilibrium chemical network. We find that CRs [injected with 10 per cent of the supernova (SN) energy] efficiently support the launching of outflows and strongly affect their phase structure. Outflows leaving the midplane are denser (rho similar to 10(-26) g cm(-3)), colder (similar to 10(4) K) and slower (similar to 30 km s(-1)) if CRs are considered in addition to thermal SNe. The CR-supported outflows are also smoother, in particular at larger heights (>1 kpc above the midplane) without the direct impact of SN explosions. Approximately, 5 per cent-25 per cent of the injected CR energy is lost via hadronic cooling. Smaller diffusion coefficients lead to slightly larger hadronic losses but allow for steeper CR pressure gradients, stronger outflows and larger accelerations. Up to a height of z similar to 1 kpc, there are large volumes in approximate pressure equilibrium between the thermal and the CR component. At larger altitudes, the CR pressure is 10-100 times as large as the thermal counterpart. More than similar to 1 kpc away from the midplane, CRs provide the dominant gas acceleration mechanism.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Girichidis, Philipp UNSPECIFIED UNSPECIFIED UNSPECIFIED Naab, Thorsten UNSPECIFIED orcid.org/0000-0002-7314-2558 UNSPECIFIED Hanasz, Michal UNSPECIFIED orcid.org/0000-0002-2370-5631 UNSPECIFIED Walch, Stefanie UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-175418
DOI:	10.1093/mnras/sty1653
Journal or Publication Title:	Mon. Not. Roy. Astron. Soc.
Volume:	479
Number:	3
Page Range:	S. 3042 - 3068
Date:	2018
Publisher:	OXFORD UNIV PRESS
Place of Publication:	OXFORD
ISSN:	1365-2966
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language TURBULENT INTERSTELLAR-MEDIUM; STAR-FORMING GALAXIES; SUPERNOVA-DRIVEN TURBULENT; ABSORPTION-LINE PROBES; GIANT MOLECULAR CLOUDS; NEUTRAL ATOMIC PHASES; LYMAN BREAK GALAXIES; DISK GALAXIES; MOVING-MESH; PARTICLE-ACCELERATION Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/17541