Journal Article

Revealing components of the galaxy population through non-parametric techniques

Steven P. Bamford, Alex L. Rojas, Robert C. Nichol, Christopher J. Miller, Larry Wasserman, Christopher R. Genovese and Peter E. Freeman

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 391, issue 2, pages 607-616
Published in print December 2008 | ISSN: 0035-8711
Published online November 2008 | e-ISSN: 1365-2966 | DOI:
Revealing components of the galaxy population through non-parametric techniques

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The distributions of galaxy properties vary with environment, and are often multimodal, suggesting that the galaxy population may be a combination of multiple components. The behaviour of these components versus environment holds details about the processes of galaxy development. To release this information we apply a novel, non-parametric statistical technique, identifying four components present in the distribution of galaxy Hα emission-line equivalent widths. We interpret these components as passive, star forming and two varieties of active galactic nuclei. Independent of this interpretation, the properties of each component are remarkably constant as a function of environment. Only their relative proportions display substantial variation. The galaxy population thus appears to comprise distinct components which are individually independent of environment, with galaxies rapidly transitioning between components as they move into denser environments.

Keywords: methods: statistical; galaxies: clusters: general; galaxies: fundamental parameters; galaxies: statistics

Journal Article.  6798 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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