Universität zu Köln

Hu, Chia-Yu ORCID: 0000-0002-9235-3529, Naab, Thorsten ORCID: 0000-0002-7314-2558, Walch, Stefanie, Glover, Simon C. O. and Clark, Paul C. (2016). Star formation and molecular hydrogen in dwarf galaxies: a non-equilibrium view. Mon. Not. Roy. Astron. Soc., 458 (4). S. 3528 - 3554. OXFORD: OXFORD UNIV PRESS. ISSN 1365-2966

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Abstract

We study the connection of star formation to atomic (Hi) and molecular hydrogen (H-2) in isolated, low-metallicity dwarf galaxies with high-resolution (m(gas) = 4 M-circle dot, N-ngb = 100) smoothed particle hydrodynamics simulations. The model includes self-gravity, non equilibrium cooling, shielding from a uniform and constant interstellar radiation field, the chemistry of H-2 formation, H-2-independent star formation, supernova feedback and metal enrichment. We find that the H-2 mass fraction is sensitive to the adopted dust-to-gas ratio and the strength of the interstellar radiation field, while the star formation rate is not. Star formation is regulated by stellar feedback, keeping the gas out of thermal equilibrium for densities n < 1 cm(-3). Because of the long chemical time-scales, the H-2 mass remains out of chemical equilibrium throughout the simulation. Star formation is well correlated with cold (T <= 100 K) gas, but this dense and cold gas the reservoir for star formation-is dominated by H-1, not H-2. In addition, a significant fraction of H2 resides in a diffuse, warm phase, which is not star-forming. The interstellar medium is dominated by warm gas (100 K < T < 3 x 10(4) K) both in mass and in volume. The scaleheight of the gaseous disc increases with radius while the cold gas is always confined to a thin layer in the mid-plane. The cold gas fraction is regulated by feedback at small radii and by the assumed radiation field at large radii. The decreasing cold gas fractions result in a rapid increase in depletion time (up to 100 Gyr) for total gas surface densities Sigma(H1+H2) less than or similar to 10 M-circle dot pc(-2), in agreement with observations of dwarf galaxies in the Kennicutt-Schmidt plane.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Hu, Chia-Yu UNSPECIFIED orcid.org/0000-0002-9235-3529 UNSPECIFIED Naab, Thorsten UNSPECIFIED orcid.org/0000-0002-7314-2558 UNSPECIFIED Walch, Stefanie UNSPECIFIED UNSPECIFIED UNSPECIFIED Glover, Simon C. O. UNSPECIFIED UNSPECIFIED UNSPECIFIED Clark, Paul C. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-274189
DOI:	10.1093/mnras/stw544
Journal or Publication Title:	Mon. Not. Roy. Astron. Soc.
Volume:	458
Number:	4
Page Range:	S. 3528 - 3554
Date:	2016
Publisher:	OXFORD UNIV PRESS
Place of Publication:	OXFORD
ISSN:	1365-2966
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SMOOTHED PARTICLE HYDRODYNAMICS; MODELING CO EMISSION; GAS DEPLETION TIME; INTERSTELLAR-MEDIUM; FORMATION LAW; GALACTIC OUTFLOWS; COLUMN DENSITIES; SPIRAL GALAXIES; MOMENTUM INPUT; X FACTOR Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/27418