Redshift z ∼ 1 field galaxies observed with the keck telescope and the hubble space telescope

David C. Koo, Nicole P. Vogt, Andrew C. Phillips, Rafael Guzmán, K. L. Wu, S. M. Faber, Caryl Gronwall, Duncan A. Forbes, Garth D. Illingworth, Edward J. Groth, Marc Davis, Richard G. Kron, Alexander S. Szalay

Research output: Contribution to journalArticlepeer-review


We report results based on 35 new spectroscopic redshifts obtained with the Keck Telescope for field galaxies that also have photometry and morphology from survey images taken by the refurbished Hubble Space Telescope. A sample of 24 redshifts for galaxies fainter than I = 22 has a median redshift of z ∼ 0.81. This result is inconsistent with the lower median redshift of z ∼ 0.6 predicted by the "maximal merger models" of Carlberg, which otherwise fit existing data. The data match an extrapolation of the Canada France Redshift Survey (CFRS), as well as predictions of certain mild luminosityevolution models. Nearly half of the redshifts lie in two structures at z ≃ 0.81 and z ≃ 1.0, showing the presence of high-density concentrations spanning scales of ∼1 h-1 Mpc, i.e., the size of groups. We find emission lines or the presence of possible neighbors in seven of nine otherwise luminous galaxies with red central regions at redshifts beyond z ∼ 0.7. We also note a diversity of morphological types among blue galaxies at z ∼ 1, including small compact galaxies, "chains," and "blue nucleated galaxies." These morphologies are found among local, but generally less luminous, galaxies. Distant blue galaxies also include apparently normal late-type spirals. These findings could imply modest bursts of star formation caused by mergers or interactions of small, gas-rich galaxies with each other or with larger, well-formed galaxies. This first glimpse of very faint z ∼ 1 field galaxies of diverse colors and morphologies suggests that a mixture of physical processes is at work in the formation and evolution of faint field galaxies.

Original languageEnglish (US)
Pages (from-to)535-541
Number of pages7
JournalAstrophysical Journal
Issue number2 PART I
StatePublished - 1996


  • Cosmology: observations
  • Galaxies: distances and redshifts
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Redshift z ∼ 1 field galaxies observed with the keck telescope and the hubble space telescope'. Together they form a unique fingerprint.

Cite this