Journal Article

Quantifying galactic morphological transformations in the cluster environment

B. Cervantes-Sodi, Changbom Park, X. Hernandez and Ho Seong Hwang

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 1, pages 587-595
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI:
Quantifying galactic morphological transformations in the cluster environment

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We study the effects of the cluster environment on galactic morphology by defining a dimensionless angular momentum parameter, λd, to obtain a quantitative and objective measure of galaxy type. The use of this physical parameter allows us to take the study of morphological transformations in clusters beyond the measurements of merely qualitative parameters, e.g. spiral/elliptical (S/E) ratios, to a more physical footing. To this end, we employ an extensive Sloan Digital Sky Survey sample (Data Release 7) with galaxies associated with Abell galaxy clusters. The sample contains 121 relaxed Abell clusters and over 51 000 individual galaxies, which guarantees a thorough statistical coverage over a wide range of physical parameters. We find that the median λd value tends to decrease as we approach the cluster centre, with different dependences according to the mass of the galaxies and the hosting cluster; low- and intermediate-mass galaxies show a strong dependence, while massive galaxies seem to show, at all radii, low λd values. By analysing trends in λd as functions of the nearest neighbour environment, clustercentric radius and velocity dispersion of clusters, we can identify clearly the leading physical processes at work. We find that in massive clusters (σ > 700 km s−1), the interaction with the cluster central region dominates, whilst in smaller clusters galaxy–galaxy interactions are chiefly responsible for driving galactic morphological transformations.

Keywords: galaxies: clusters: general; galaxies: fundamental parameters; galaxies: interactions; galaxies: statistics; galaxies: structure; cosmology: observations

Journal Article.  7718 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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