Extremely red objects in the Lockman hole

G. Wilson, J. S. Huang, P. G. Pérez-González, E. Egami, R. J. Ivison, J. R. Rigby, A. Alonso-Herrero, P. Barmby, H. Dole, G. G. Fazio, E. Le Floc'h, C. Papovich, D. Rigopoulou, L. Bai, C. W. Engelbracht, D. Frayer, K. D. Gordon, D. C. Hines, K. A. Misselt, S. MiyazakiJ. E. Morrison, G. H. Rieke, M. J. Rieke, J. Surace

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


We investigate extremely red objects (EROs) using near- and mid-infrared observations in five passbands (3.6 to 24 μm) obtained from the Spitzer Space Telescope, and deep ground-based R and K imaging. The great sensitivity of the Infrared Array Camera (IRAC) camera allows us to detect 64 EROs (a surface density of 2.90 ± 0.36 arcmin-2; [3.6]AB < 23.7) in only 12 minutes of IRAC exposure time, by means of an R - [3.6] color cut (analogous to the traditional red R - K cut). A pure infrared K - [3.6] red cut detects a somewhat different population and may be more effective at selecting z > 1.3 EROs. We find ∼17% of all galaxies detected by IRAC at 3.6 or 4.5 μm to be EROs. These percentages rise to about 40% at 5.8 μm, and about 60% at 8.0 μm. We utilize the spectral bump at 1.6 μm to divide the EROs into broad redshift slices using only near-infrared colors (2.2/3.6/4.5 μm). We conclude that two-thirds of all EROs lie at redshift z > 1.3. Detections at 24 μm imply that at least 11% of 0.6 < z < 1.3 EROs and at least 22% of z > 1.3 EROs are dusty star-forming galaxies.

Original languageEnglish (US)
Pages (from-to)107-111
Number of pages5
JournalAstrophysical Journal, Supplement Series
Issue number1
StatePublished - Sep 2004


  • Cosmology: Observations
  • Galaxies: Evolution
  • Galaxies: High-redshift
  • Galaxies: Photometry
  • Galaxies: Starburst
  • Infrared: Galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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