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Why are some galaxy discs extremely thin?

Banerjee, Arunima and Jog, Chanda J (2013) Why are some galaxy discs extremely thin? In: Monthly Notices of the Royal Astronomical Society, 431 (1). pp. 582-588.

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Official URL: http://dx.doi.org/10.1093/mnras/stt186

Abstract

Some low-surface-brightness galaxies are known to have extremely thin stellar discs with the vertical-to-planar axes ratio 0.1 or less, often referred to as superthin galaxies. Although their existence is now known for over three decades, the physical origin of the superthin discs is still not understood. We model the vertical thickness of the stellar disc using our model of a two-component (gravitationally coupled stars and gas) disc embedded in a dark matter halo, for a bulgeless, superthin galaxy UGC 7321 which has a dense, compact halo, and is compare with a typical dwarf irregular galaxy Holmberg II which has a low-density, non-compact halo. We show that while the presence of gas does constrain the stellar disc thickness and hence its axial ratio, it is the compact dark matter halo which plays the decisive role in determining the mean distribution of stars in the vertical direction in low-luminosity bulgeless galaxies like UGC 7321, and causes the stellar disc to be superthin. Thus, the compactness of the dark matter halo significantly affects the disc structure and this could be important for the early evolution of galaxies.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Oxford University Press
Keywords: Galaxies: Haloes; Galaxies: Individual: UGC 7321; Galaxies: Individual: Holmberg II; Galaxies: ISM; Galaxies: Kinematics and Dynamics; Galaxies: Structure
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Depositing User: Francis Jayakanth
Date Deposited: 17 Jun 2013 07:58
Last Modified: 17 Jun 2013 07:58
URI: http://eprints.iisc.ac.in/id/eprint/46694

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