X-ray nondetection of the Lyman-alpha Emitters at z ~ 4.5Report as inadecuate



 X-ray nondetection of the Lyman-alpha Emitters at z ~ 4.5


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The Lyman-alpha emitters found at z ~ 4.5 by the Large Area Lyman Alpha LALA survey have high equivalent widths in the Lyman-alpha 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 Lyman-alpha emitters. The 172 ks deep Chandra image on the LALA Bootes field was presented in a previous paper Malhotra et al. 2003, and in this paper we present a new Chandra deep exposure 174 ks on the LALA Cetus field, which doubled our sample of X-ray imaged Lyman-alpha sources, and imaged the brightest source among our Lyman-alpha emitters. None of the 101 Lyman-alpha sources covered by two Chandra exposures was detected individually in X-ray, with a 3 sigma limiting X-ray flux of F {0.5-10.0 keV} 3.3 x 10^{-16} ergs-cm^2-s for on-axis targets. The sources remain undetectable in the stacked image, implying a 3 sigma limit to the average luminosity of L {2-8keV} 2.8 x 10^{42} ergs-s. The resulting X-ray to Lyman-alpha ratio is 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 Lyman-alpha emitters at z ~ 4.5.



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

Source: https://archive.org/







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