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Hierarchical formation of bulgeless galaxies: why outflows have low angular momentum


Brook, C B; Governato, F; Roskar, R; Stinson, G; Brooks, A M; Wadsley, J; Quinn, T; Gibson, B K; Snaith, O; Pilkington, K; House, E; Pontzen, A (2011). Hierarchical formation of bulgeless galaxies: why outflows have low angular momentum. Monthly Notices of the Royal Astronomical Society, 415(2):1051-1060.

Abstract

Using high resolution, fully cosmological smoothed particle hydrodynamical simulations of dwarf galaxies in a Lambda cold dark matter Universe, we show how high redshift gas outflows can modify the baryon angular momentum distribution and allow pure disc galaxies to form. We outline how galactic outflows preferentially remove low angular momentum material due a combination of (a) star formation peaking at high redshift in shallow dark matter potentials, an epoch when accreted gas has relatively low angular momentum, (b) the existence of an extended reservoir of high angular momentum gas in the outer disc to provide material for prolonged SF at later times and (c) the tendency for outflows to follow the path of least resistance which is perpendicular to the disc. We also show that outflows are enhanced during mergers, thus expelling much of the gas which has lost its angular momentum during these events, and preventing the formation of ‘classical’, merger driven bulges in low-mass systems. Stars formed prior to such mergers form a diffuse, extended stellar halo component similar to those detected in nearby dwarfs.

Abstract

Using high resolution, fully cosmological smoothed particle hydrodynamical simulations of dwarf galaxies in a Lambda cold dark matter Universe, we show how high redshift gas outflows can modify the baryon angular momentum distribution and allow pure disc galaxies to form. We outline how galactic outflows preferentially remove low angular momentum material due a combination of (a) star formation peaking at high redshift in shallow dark matter potentials, an epoch when accreted gas has relatively low angular momentum, (b) the existence of an extended reservoir of high angular momentum gas in the outer disc to provide material for prolonged SF at later times and (c) the tendency for outflows to follow the path of least resistance which is perpendicular to the disc. We also show that outflows are enhanced during mergers, thus expelling much of the gas which has lost its angular momentum during these events, and preventing the formation of ‘classical’, merger driven bulges in low-mass systems. Stars formed prior to such mergers form a diffuse, extended stellar halo component similar to those detected in nearby dwarfs.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:April 2011
Deposited On:18 Feb 2012 19:57
Last Modified:05 Apr 2016 14:55
Publisher:Wiley-Blackwell
ISSN:0035-8711 (P) 1365-2966 (E)
Additional Information:The definitive version is available at www3.interscience.wiley.com
Publisher DOI:https://doi.org/10.1111/j.1365-2966.2011.18545.x
Related URLs:http://arxiv.org/abs/1010.1004

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