Journal Article

Witnessing the active assembly phase of massive galaxies since <i>z</i>= 1

Y. Matsuoka and K. Kawara

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 405, issue 1, pages 100-110
Published in print June 2010 | ISSN: 0035-8711
Published online June 2010 | e-ISSN: 1365-2966 | DOI:
Witnessing the active assembly phase of massive galaxies since z= 1

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We present an analysis of ∼60 000 massive (stellar mass M > 1011 M) galaxies out to z= 1 drawn from 55.2 deg2 of the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) and the Sloan Digital Sky Survey (SDSS) II Supernova Survey. This is by far the largest survey of massive galaxies with robust mass estimates, based on infrared (K-band) photometry, reaching to the Universe at about half its present age. We find that the most massive (M > 1011.5 M) galaxies have experienced rapid growth in number since z= 1, while the number densities of the less massive systems show rather mild evolution. Such a hierarchical trend of evolution is consistent with the predictions of the current semi-analytic galaxy formation model based on ΛCDM theory. While the majority of massive galaxies are red-sequence populations, we find that a considerable fraction of galaxies are blue star-forming galaxies. The blue fraction is smaller in more massive systems and decreases toward the local Universe, leaving the red, most massive galaxies at low redshifts, which would support the idea of active ‘bottom-up’ formation of these populations during 0 < z < 1.

Keywords: galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: formation; galaxies: luminosity function, mass function; galaxies: stellar content; cosmology: observations

Journal Article.  8374 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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