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Title: A search for H I 21 cm absorption toward the highest redshift (z~5.2) radio-loud objects
Authors: Carilli, C.L.
Wang, Ran
van Hoven, M.B.
Dwarakanath, K.S.
Chengalur, J.N.
Wyithe, Stuart
Issue Date: Jun-2007
Publisher: The University of Chicago Press for the American Astronomical Society
Citation: The Astronomical Journal, 2007, Vol.133, p2841-2845
Abstract: 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 σ 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(H I)<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.
Description: Restricted Access. An open-access version is available at Articles older than 2 years are open to all at the journal site (alternative location)
ISSN: 0004-6256
1538-3881 (online)
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Copyright: 2007 The American Astronomical Society
Appears in Collections:Research Papers (A&A)

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