Keck spectroscopy of faint 3 > z > 7 Lyman break galaxies: A high fraction of line emitters at redshift six

Daniel P Stark, Richard S. Ellis, Masami Ouchi

Research output: Contribution to journalArticle

145 Citations (Scopus)

Abstract

As Lyα photons are scattered by neutral hydrogen, a change with redshift in the Lyα equivalent width (EW) distribution of distant galaxies offers a promising probe of the degree of ionization in the intergalactic medium and hence when cosmic reionization ended. This simple test is complicated by the fact that Lyα emission can also be affected by variations in the kinematics and dust content of the host galaxies. In the first paper in this series, we demonstrated both a luminosity-and redshift-dependent trend in the fraction of Lyα emitters seen within color-selected "Lyman break" galaxies (LBGs) over the range 3 < z < 6; lower luminosity galaxies and those at higher redshift show an increased likelihood of strong emission. Here, we present the results from 12.5 hr exposures with the Keck DEIMOS spectrograph focused primarily on LBGs at z ≃ 6 which enable us to confirm the redshift dependence of line emission more robustly and to higher redshift than was hitherto possible. We find that 54% ± 11% of faint z ≃ 6 LBGs show strong (WLyα,0 > 25 Å) emission, an increase of 55% from a sample of similarly luminous z ≃ 4 galaxies. With a total sample of 74 z ≃ 6 LBGs, we determine the luminosity-dependent Lyα EW distribution. Assuming continuity in these trends to the new population of z ≃ 7 sources located with the Hubble WFC3/IR camera, we predict that unless the neutral fraction rises in the intervening 200 Myr, the success rate for spectroscopic confirmation using Lyα emission should be high.

Original languageEnglish (US)
JournalAstrophysical Journal Letters
Volume728
Issue number1 PART II
DOIs
StatePublished - Feb 10 2011
Externally publishedYes

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emitters
spectroscopy
galaxies
luminosity
ionization
trends
kinematics
probe
hydrogen
intergalactic media
dust
continuity
cameras
color
probes
photons
distribution
trend
rate
test

Keywords

  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: high-redshift
  • Galaxies: starburst

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Keck spectroscopy of faint 3 > z > 7 Lyman break galaxies : A high fraction of line emitters at redshift six. / Stark, Daniel P; Ellis, Richard S.; Ouchi, Masami.

In: Astrophysical Journal Letters, Vol. 728, No. 1 PART II, 10.02.2011.

Research output: Contribution to journalArticle

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