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Lopsided spiral galaxies: evidence for gas accretion

Bournaud, F and Combes, F and Jog, CJ and Puerari, I (2005) Lopsided spiral galaxies: evidence for gas accretion. In: Astronomy and Astrophysics, 438 (2). pp. 507-520.

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Abstract

We quantify the degree of lopsidedness for a sample of 149 galaxies observed in the near-infrared from the OSUBGS sample, and try to explain the physical origin of the observed disk lopsidedness. We confirm previous studies, but for a larger sample, that a large fraction of galaxies have significant lopsidedness in their stellar disks, measured as the Fourier amplitude of the m=1 component normalised to the average or m=0 component in the surface density. Late-type galaxies are found to be more lopsided, while the presence of m=2 spiral arms and bars is correlated with disk lopsidedness. We also show that the m=1 amplitude is uncorrelated with the presence of companions. Numerical simulations were carried out to study the generation of m=1 via different processes: galaxy tidal encounters, galaxy mergers, and external gas accretion with subsequent star formation. These simulations show that galaxy interactions and mergers can trigger strong lopsidedness, but do not explain several independent statistical properties of observed galaxies. To explain all the observational results, it is required that a large fraction of lopsidedness results from cosmological accretion of gas on galactic disks, which can create strongly lopsided disks when this accretion is asymmetrical enough.

Item Type: Journal Article
Additional Information: The copyright for this article belongs to EDP Sciences.
Keywords: galaxies: evolution;galaxies: formation;galaxies: structure;galaxies: spiral
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 22 Sep 2005
Last Modified: 27 Aug 2008 11:28
URI: http://eprints.iisc.ernet.in/id/eprint/3693

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