Multi-wavelength study of a complete IRAC 3.6 μm selected galaxy sample: A fair census of red and blue populations at redshifts 0.4-1.2

J. S. Huang, S. M. Faber, C. N.A. Willmer, D. Rigopoulou, D. Koo, J. Newman, C. Shu, M. L.N. Ashby, P. Barmby, A. Coil, Z. Luo, G. Magdis, T. Wang, B. Weiner, S. P. Willner, X. Z. Zheng, G. G. Fazio

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


We present a multi-wavelength study of a 3.6 μm selected galaxy sample in the Extended Groth Strip (EGS). The sample is complete for galaxies with stellar mass >109.5 Mȯ and redshift 0.4 < z < 1.2. In this redshift range, the Infrared Array Camera 3.6 μm band measures the rest-frame near-infrared band, permitting nearly unbiased selection with respect to both quiescent and star-forming galaxies. The numerous spectroscopic redshifts available in the EGS are used to train an artificial neural network to estimate photometric redshifts. The distribution of photometric redshift errors is Gaussian with standard deviation ∼0.025(1 + z), and the fraction of redshift failures (>3σ errors) is about 3.5%. A new method of validation based on pair statistics confirms the estimate of standard deviation even for galaxies lacking spectroscopic redshifts. Basic galaxy properties measured include rest-frame U-B colors, B- and K-band absolute magnitudes, and stellar masses. We divide the sample into quiescent and star-forming galaxies according to their rest-frame U-B colors and 24-3.6 μm flux density ratios and derive rest K-band luminosity functions and stellar mass functions for quiescent, star-forming, and all galaxies. The results show that massive, quiescent galaxies were in place by z ≈ 1, but lower mass galaxies generally ceased their star formation at later epochs.

Original languageEnglish (US)
Article number21
JournalAstrophysical Journal
Issue number1
StatePublished - Mar 20 2013


  • cosmology: observations
  • galaxies: distances and redshifts
  • galaxies: evolution
  • galaxies: luminosity function, mass function

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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