The properties and evolution of a K-band selected sample of massive galaxies at z ∼ 0.4-2 in the Palomar/DEEP2 survey

C. J. Conselice, K. Bundy, I. Trujillo, A. Coil, P. Eisenhardt, R. S. Ellis, A. Georgakakis, J. Huang, J. Lotz, K. Nandra, J. Newman, C. Papovich, B. Weiner, C. Willmer

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113 Scopus citations

Abstract

We present the results of a study on the properties and evolution of massive (M* > 1011 M⊙) galaxies at z ∼ 0.4-2 utilizing Keck spectroscopy, near-infrared Palomar imaging, and Hubble, Chandra and Spitzer data covering fields targeted by the DEEP2 galaxy spectroscopic survey. Our sample is K-band selected and stellar mass limited, based on wide-area near-infrared imaging from the Palomar Observatory Wide-Field Infrared Survey, which covers 1.53 deg2 to a 5σ depth of Ks,vega ∼ 20.5. Our primary goal is to obtain a broad census of massive galaxies through measuring how their number and mass densities, morphology, as well as their star formation and active galactic nucleus content evolve from z ∼ 0.4-2. Our major findings include: (i) statistically the mass and number densities of M* > 1011 M galaxies show little evolution between z = 0 and 1 and from z ∼ 0 to 2 for M* > 1011.5 M galaxies. We however find significant evolution within 1 < z < 1.5 for 1011 M < M* < 10 11.5 M galaxies. (ii) After examining the structures of our galaxies using Hubble ACS imaging, we find that M* > 1011 M selected galaxies show a nearly constant elliptical fraction of ∼70-90 per cent at all redshifts. The remaining objects tend to be peculiars possibly undergoing mergers at z > 0.8, while spirals dominate the remainder at lower redshifts. A significant fraction (∼25 per cent) of these early-types contain minor structural anomalies. (iii) We find that only a fraction (∼60 per cent) of massive galaxies with M* > 1011 M are on the red sequence at z ∼ 1.4, while nearly 100 per cent evolve on to it by z ∼ 0.4. (iv) By utilizing Spitzer MIPS imaging and [O ii] line fluxes we argue that M* > 1011.5 M galaxies have a steeply declining star formation rate (SFR) density ∼ (1 + z)6. By examining the contribution of star formation to the evolution of the mass function, as well as the merger history through the CAS parameters, we determine that M* > 1011 M galaxies undergo on average 0.9+0.7-0.5 major mergers at 0.4 < z < 1.4. (v) We find that a high (5 per cent) fraction of all M * > 1011 M galaxies are X-ray emitters. Roughly half of these are morphologically distorted ellipticals or peculiars. Finally, we compare our mass growth with semi-analytical models from the Millennium Simulation, finding relative good agreement at z < 2 for the M* < 1011.5 M systems, but that the number and mass densities of M* > 1011.5 M galaxies are underpredicted by a factor of >100.

Original languageEnglish (US)
Pages (from-to)962-986
Number of pages25
JournalMonthly Notices of the Royal Astronomical Society
Volume381
Issue number3
DOIs
StatePublished - Nov 2007

Keywords

  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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