Redshifted H I and OH absorption in radio galaxies and quasars
Artikel i vetenskaplig tidskrift, 2011

From a survey for the redshifted H i 21-cm and OH 18-cm absorption in the hosts of a sample of radio galaxies and quasars, we detect H i in three of the 10 and OH in none of the 14 sources for which useful data were obtained. As expected from our recent result, all of the 21-cm detections occur in sources with ultraviolet (UV) continuum luminosities of L(UV) < 1023 W Hz-1. At these 'moderate' luminosities, we also obtain four non-detections, although, as confirmed by the equipartition of detections between the type 1 and type 2 objects, this near-50 per cent detection rate cannot be attributed to unified schemes of active galactic nuclei (AGNs). All of our detections are at redshifts of z less than or similar to 0.67, which, in conjunction with our faint source selection, biases against UV luminous objects. The importance of the UV luminosity (over AGN type) in the detection of the 21-cm absorption is further supported by the non-detections in the two high-redshift (z similar to 3.6-3.8) radio galaxies, which are both type 2 objects, while having L(UV) > 1023 W Hz-1. Our 21-cm detections in combination with those previously published give a total of eight (associated and intervening) H i-absorbing sources searched and undetected in OH. Using the detected 21-cm line strengths to normalize the limits, we find that only two of these eight sources may have been searched sufficiently deeply in OH, even though these are marginal.

galaxies: fundamental parameters

active galactic nuclei

optical-spectra

radio lines: galaxies

absorbing gas

high-redshift

fundamental constants

unified schemes

flat-spectrum sample

galaxies:

galaxies: active

red quasars

absorption

sky survey

quasars: absorption lines

molecular

ultraviolet: galaxies

21 cm absorption

Författare

S.J. Curran

University of New South Wales (UNSW)

M. T. Whiting

Australia Telescope National Facility

University of New South Wales (UNSW)

M. T. Murphy

University of Cambridge Institute of Astronomy

Swinburne University of Technology

J. K. Webb

University of New South Wales (UNSW)

C. Bignell

National Radio Astronomy Observatory

A. G. Polatidis

Max Planck-institutet

Netherlands Institute for Radio Astronomy (ASTRON)

Tommy Wiklind

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

P. Francis

Australian National University

G. Langston

National Radio Astronomy Observatory

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 413 1165-1173

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1111/j.1365-2966.2011.18209.x