X-ray properties of lyman break galaxies in the great observatories origins deep survey

B. D. Lehmer, W. N. Brandt, D. M. Alexander, F. E. Bauer, C. J. Conselice, M. E. Dickinson, M. Giavalisco, N. A. Grogin, A. M. Koekemoer, K. S. Lee, L. A. Moustakas, D. P. Schneider

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Abstract

We constrain the X-ray emission properties of Lyman break galaxies (LBGs) at z ≈ 3-6 using the ≈2 Ms Chandra Deep Field North and ≈1 Ms Chandra Deep Field South. Large samples of LBGs were discovered using the Hubble Space Telescope as part of the Great Observatories Origins Deep Survey (GOODS). Deep optical and X-ray imaging over the GOODS fields have allowed us to place the most significant constraints on the X-ray properties of LBGs to date. Mean X-ray properties of 449, 1734, 629, and 247 LBGs with z ∼3, 4, 5, and 6, respectively, were determined using stacking techniques. When stacked, we detect X-ray emission from LBGs at z ∼3 (∼7 σ) and from an optically bright subset (brightest 25%) of LBGs at z ∼4 (∼3 σ); the latter is the highest redshift detection yet for "normal" galaxies in the X-ray band. The effective exposure times for these stacked observations are ≈0.7 and 0.5 Gs, respectively. The derived average rest-frame 2.0-8.0 keV luminosities are 1.5 × 10 41 and 1.4 × 10 41 ergs s -1, respectively. X-ray emission from these LBGs is likely due to high-mass X-ray binaries and Type II supernovae; the corresponding star formation rates are ≈10-30 M⊙ yr -1. The X-ray-to-B-band mean luminosity ratio (L X/L B) at z ∼3 is somewhat elevated with respect to that measured for starburst galaxies in the local universe (significance ∼3 σ). When stacking full samples of LBGs at z ∼4, 5, and 6, we do not obtain significant detections (<3 σ) and derive rest-frame 2.0-8.0 keV luminosity upper limits (3 σ) of 0.9, 2.8, and 7.1 × 10 41 ergs s -1, respectively. These upper limits constrain any widespread active galactic nucleus (AGN) activity in these objects to be modest at best. Furthermore, we find that ∼0.5% of our LBGs from z ≈3 to z ≈6 are detected individually in the X-ray band. These LBGs have spectral shapes and luminosities characteristic of moderate-power AGNs (e.g., Seyfert galaxies and quasars).

Original languageEnglish (US)
Pages (from-to)1-8
Number of pages8
JournalAstronomical Journal
Volume129
Issue number1
DOIs
StatePublished - Jan 2005

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Lehmer, B. D., Brandt, W. N., Alexander, D. M., Bauer, F. E., Conselice, C. J., Dickinson, M. E., Giavalisco, M., Grogin, N. A., Koekemoer, A. M., Lee, K. S., Moustakas, L. A., & Schneider, D. P. (2005). X-ray properties of lyman break galaxies in the great observatories origins deep survey. Astronomical Journal, 129(1), 1-8. https://doi.org/10.1086/426335