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Role of gas in supporting grand spiral structure

Ghosh, Soumavo and Jog, Chanda J (2015) Role of gas in supporting grand spiral structure. In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 451 (2). pp. 1350-1355.

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Official URL: http://dx.doi.org/10.1093/mnras/stv1040


The density wave theory for the grand-design two-armed spiral pattern in galaxies is successful in explaining several observed features. However, the long-term persistence of this spiral structure is a serious problem since the group transport would destroy it within about a billion years as shown in a classic paper by Toomre. In this paper, we include the low-velocity dispersion component, namely gas, on an equal footing with stars in the formulation of the density wave theory, and obtain the dispersion relation for this coupled system. We show that the inclusion of gas makes the group transport slower by a factor of few, thus allowing the pattern to persist longer - for several billion years. Though still less than the Hubble time, this helps in making the spiral structure more long-lived. Further we show that addition of gas is essential to get a stable wave for the observed pattern speed for the Galaxy, which otherwise is not possible for a one-component stellar disc.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the OXFORD UNIV PRESS, GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND
Keywords: galaxies: ISM; galaxies: kinematics and dynamics; galaxies: spiral; galaxies: structure
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 09 Oct 2015 04:47
Last Modified: 09 Oct 2015 04:47
URI: http://eprints.iisc.ac.in/id/eprint/52512

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