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Angular momentum transport and evolution of lopsided galaxies

Saha, Kanak and Jog, Chanda J (2014) Angular momentum transport and evolution of lopsided galaxies. In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 444 (1). pp. 352-363.

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Official URL: http://dx.doi.org/ 10.1093/mnras/stu1414

Abstract

The surface brightness distribution in the majority of stellar galactic discs falls off exponentially. Often what lies beyond such a stellar disc is the neutral hydrogen gas whose distribution also follows a nearly exponential profile at least for a number of nearby disc galaxies. Both the stars and gas are commonly known to host lopsided asymmetry especially in the outer parts of a galaxy. The role of such asymmetry in the dynamical evolution of a galaxy has not been explored so far. Following Lindblad's original idea of kinematic density waves, we show that the outer part of an exponential disc is ideally suitable for hosting lopsided asymmetry. Further, we compute the transport of angular momentum in the combined stars and gas disc embedded in a dark matter halo. We show that in a pure star and gas disc, there is a transition point where the free precession frequency of a lopsided mode, Omega - kappa, changes from retrograde to prograde and this in turn reverses the direction of angular momentum flow in the disc leading to an unphysical behaviour. We show that this problem is overcome in the presence of a dark matter halo, which sets the angular momentum flow outwards as required for disc evolution, provided the lopsidedness is leading in nature. This, plus the well-known angular momentum transport in the inner parts due to spiral arms, can facilitate an inflow of gas from outside perhaps through the cosmic filaments.

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: evolution; galaxies: haloes; galaxies: kinematics and dynamics; galaxies: spiral; galaxies: structure
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Depositing User: Id for Latest eprints
Date Deposited: 20 Nov 2014 04:58
Last Modified: 20 Nov 2014 04:58
URI: http://eprints.iisc.ac.in/id/eprint/50313

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