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The Thick Disks of Spiral Galaxies as Relics from Gas-Rich, Turbulent, Clumpy Disks at High Redshift

Bournaud, F, Elmegreen, BG and Martig, M (2009) The Thick Disks of Spiral Galaxies as Relics from Gas-Rich, Turbulent, Clumpy Disks at High Redshift. Astrophysical Journal Letters, 707 (1). ISSN 2041-8205

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The formation of thick stellar disks in spiral galaxies is studied. Simulations of gas-rich young galaxies show formation of internal clumps by gravitational instabilities, clump coalescence into a bulge, and disk thickening by strong stellar scattering. The bulge and thick disks of modern galaxies may form this way. Simulations of minor mergers make thick disks too, but there is an important difference. Thick disks made by internal processes have a constant scale height with galactocentric radius, but thick disks made by mergers flare. The difference arises because in the first case, perpendicular forcing and disk-gravity resistance are both proportional to the disk column density, so the resulting scale height is independent of this density. In the case of mergers, perpendicular forcing is independent of the column density and the low-density regions get thicker; the resulting flaring is inconsistent with observations. Late-stage gas accretion and thin-disk growth are shown to preserve the constant scale heights of thick disks formed by internal evolution. These results reinforce the idea that disk galaxies accrete most of their mass smoothly and acquire their structure by internal processes, in particular through turbulent and clumpy phases at high redshift.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Q Science > QD Chemistry
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society; IOP Publishing
Related URLs:
Date Deposited: 05 Oct 2017 08:57
Last Modified: 20 Apr 2022 09:29
DOI or ID number: 10.1088/0004-637X/707/1/L1
URI: https://researchonline.ljmu.ac.uk/id/eprint/7278
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