DETECTION OF 21 CENTIMETER H i ABSORPTION AT Z = 0.78 IN A SURVEY OF RADIO CONTINUUM SOURCES
نویسندگان
چکیده
We report the detection of a deep broad H I 21 cm absorption system at z = 0.78 toward the radio source [HB89] 2351+456 (4C+45.51) at z = 1.992. The H I absorption was identified in a blind spectral line survey conducted at the Green Bank Telescope spanning 0.63 < z < 1.10 toward a large sample of radio continuum sources. The H I column density is NHI = 2.35×10 (Ts/f) cm , where Ts is the spin temperature and f is the continuum covering factor of the absorbing gas. For Ts/f > 8.5 K, this system is by definition a damped Lyα absorption system (NHI ≥ 2 × 10 20 cm). The line is unusually broad, with a FWHM of 53 km s and a full span of 163 km s, suggesting a physically extended H I gas structure. Radio surveys identify damped Lyα systems in a manner that bypasses many of the selection effects present in optical/UV surveys, including dust extinction and the atmospheric cutoff for z < 1.65. The smooth broad profile of this H I 21 cm absorption system is similar to the z = 0.89 H I absorption toward PKS 1830−211, which suggests that the absorber toward [HB89] 2351+456 is also a gravitational lens and a molecular absorption system. However, very long baseline interferometry and Hubble Space Telescope observations show little evidence for gravitational lensing, and BIMA millimeter observations show no HCO (1 → 2) or HCN (1 → 2) absorption down to τ = 0.15 (3σ) in 5 km s channels. Although this radio damped Lyα selection technique would include dusty, molecule-rich systems, [HB89] 2351+456 appears to be a “vanilla” H I 21 cm absorber. Subject headings: galaxies:ISM — quasars:absorption lines — quasars: individual([HB89] 2351+456)
منابع مشابه
A survey for redshifted molecular and atomic absorption lines – II. Associated Hi, OH and millimetre lines in the z≳ 3 Parkes quarter-Jansky flat-spectrum sample
We present the results of a z ≥ 2.9 survey for H I 21-cm and molecular absorption in the hosts of radio quasars using the Giant Metrewave Radio Telescope and the Tidbinbilla 70-m telescope. Although the atomic gas has been searched to limits capable of detecting most known absorption systems, no H I was detected in any of the 10 sources. Previously published searches, which are overwhelmingly a...
متن کاملA Survey for Redshifted Molecular and Atomic Absorption Lines I. The Parkes Half-Jansky Flat-Spectrum Red Quasar Sample
We are currently undertaking a large survey for redshifted atomic and molecular absorption lines at radio frequencies. In this paper we present the results from the first phase of this: the search for H I 21-cm and OH 18-cm absorption lines in the hosts of reddened quasars and radio galaxies. Although we observed each source for up to several hours with two of the world’s most sensitive radio t...
متن کاملA Survey for Redshifted Molecular and Atomic Absorption Lines
We present the results of a z > 2.9 survey for H I 21-cm and molecular absorption in the hosts of radio quasars using the Giant Metrewave Radio Telescope and the Tidbinbilla 70m telescope. Although the atomic gas has been searched to limits capable of detecting most known absorption systems, no H I was detected in any of the ten sources. Previously published searches, which are overwhelmingly a...
متن کاملar X iv : a st ro - p h / 99 07 02 2 v 1 2 J ul 1 99 9 The Submillimeter Search for Very High Redshift Galaxies
Identifying the optical/near-infrared (NIR) counterparts to the distant submillimeter (submm) source population has proved difficult due to poor submm spatial resolution. However, the proportionality of both centimeter and submm data to the star formation rate suggests that high resolution radio continuum maps with subarcsecond positional accuracy could be exploited to locate submm sources. We ...
متن کاملMapping the Evolution of High Redshift Dusty Galaxies with Submillimeter Observations of a Radio-selected Sample
Direct submillimeter imaging has recently revealed the 850 μm background to be mostly composed of a population of distant ultraluminous infrared galaxies, but identifying the optical/near-infrared (NIR) counterparts to these sources has proved difficult due to the poor submillimeter spatial resolution. However, the proportionality of both centimeter and submillimeter data to the star formation ...
متن کامل