X-ray nondetection of the Lyα emitters at z ∼ 4.5

J. X. Wang, J. E. Rhoads, S. Malhotra, S. Dawson, D. Stern, A. Dey, T. M. Heckman, C. A. Norman, H. Spinrad

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56 Scopus citations

Abstract

The Lyα emitters found at z ∼ 4.5 by the Large Area Lyman Alpha (LALA) survey have high equivalent widths in the Lyα line, which can be produced by either narrow-lined active galactic nuclei (AGNs) or by stellar populations with a very high proportion of young, massive stars. To investigate the AGN scenario, we obtained two deep Chandra exposures to study the X-ray nature of the Lyα emitters. The 172 ks deep Chandra image on the LALA Boötes field was presented in a previous paper, and in this Letter we present a new Chandra deep exposure (174 ks) on the LALA Cetus field, which doubled our sample of X-ray-imaged Lyα sources and imaged the brightest source among our Lyα emitters. None of the 101 Lyα sources covered by two Chandra exposures were detected individually in X-rays, with a 3 σ limiting X-ray flux of F0.5-10.0 keV < 3.3 × 10 -16 ergs cm-2 s-1 for on-axis targets. The sources remain undetectable in the stacked image, implying a 3 σ limit to the average luminosity of L2-8 keV < 2.8 × 1042 ergs s-1. The resulting X-ray to Lyα ratio is greater than 21 times lower than the ratios for known high-redshift type II quasars. Together with optical spectra obtained at Keck, we conclude that no evidence of AGN activity was found among our Lyα emitters at z ∼ 4.5.

Original languageEnglish (US)
Pages (from-to)L21-L24
JournalAstrophysical Journal
Volume608
Issue number1 II
DOIs
StatePublished - Jun 10 2004

Keywords

  • Galaxies: active
  • Galaxies: high-redshift
  • Galaxies: starburst
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Wang, J. X., Rhoads, J. E., Malhotra, S., Dawson, S., Stern, D., Dey, A., Heckman, T. M., Norman, C. A., & Spinrad, H. (2004). X-ray nondetection of the Lyα emitters at z ∼ 4.5. Astrophysical Journal, 608(1 II), L21-L24. https://doi.org/10.1086/422311