A search for HI 21 cm absorption toward the highest redshift (z ~ 5.2) radio-loud objects

Carilli, C. L. ; Wang, Ran ; van Hoven, M. B. ; Dwarakanath, K. ; Chengalur, Jayaram N. ; Wyithe, Stuart (2007) A search for HI 21 cm absorption toward the highest redshift (z ~ 5.2) radio-loud objects The Astronomical Journal, 133 (6). pp. 2841-2845. ISSN 0004-637X

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Official URL: http://iopscience.iop.org/1538-3881/133/6/2841

Related URL: http://dx.doi.org/10.1086/518436


We have searched for H I 21 cm absorption toward the two brightest radio AGNs at high redshift, J0924-2201 at z = 5.20 and J0913+5919 at z = 5.11, using the Giant Metrewave Radio Telescope. These data set a 3 s upper limit to absorption of <30% at 40 km s−1 resolution for the 30 mJy source J0913+5919, and <3% for the 0.55 Jy source J0924-2201 at 20 km s−1 resolution. For J0924-2201, limits to broader lines at the few percent level are set by residual spectral baseline structure. For J0924-2201 the column density limit per 20 km s −1 channel is N(HI ) < 2.2 × 1018Ts cm−2 over a velocity range of −700 to +1180 km s−1 centered on the galaxy redshift determined through CO emission, assuming a covering factor of 1. For J0913+5919 the column density limit per 40 km s−1 channel is N(H I) < 2.2 × 1019Ts cm−2 within ±2400 km s−1 of the optical redshift. These data rule out any cool, high column density H I clouds within roughly ±1000 km s−1 of the galaxies, as are often seen in compact steep-spectrum radio AGNs, or clouds that might correspond to residual gas left over from cosmic reionization.

Item Type:Article
Source:Copyright of this article belongs to University of Chicago Press.
Keywords:Cosmology: Observations; Galaxies: High-redshift; Radio Lines: Galaxies
ID Code:63571
Deposited On:29 Sep 2011 04:09
Last Modified:29 Sep 2011 04:09

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