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X-ray nondetection of the Lyman-alpha 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
; | | Date: |
30 Apr 2004 | | Journal: | Astrophys.J. 608 (2004) L21-L24 | | Subject: | astro-ph | | Abstract: | 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. | | Source: | arXiv, astro-ph/0404611 | | Services: | Forum | Review | PDF | Favorites | |
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