On the absence of molecular absorption in high-redshift millimetre-band searches
Artikel i vetenskaplig tidskrift, 2011

We have undertaken a search for millimetre-waveband absorption (through the CO and HCO(+) rotational transitions) in the host galaxies of reddened radio sources (z = 0.405-1.802). Despite the colour selection (optical-near-infrared colours of V - K greater than or similar to 5 in all but one source), no absorption was found in any of the eight quasars for which the background continuum flux was detected. On the basis of the previous (mostly intervening) H(2) and OH detections, the limits reached here and in some previous surveys should be deep enough to detect molecular absorption according to their V - K colours. However, our survey makes the assumption that the reddening is associated with dust close to the emission redshift of the quasar and that the narrow millimetre component of this emission is intercepted by the compact molecular cores. By using the known millimetre absorbers to define the colour depth and comparing this with the ultraviolet luminosities of the sources, we find that, even if these assumptions are valid, only 12 of the 40 objects (mainly from this work) are potentially detectable. This is assuming an excitation temperature of T(x) = 10 K at z = 0, with the number decreasing with increasing temperatures (to zero detectable at T(x) greater than or similar to 100 K).


galaxies: high-redshift

lyman-alpha systems

radio lines:



galaxies: active


galaxies: abundances

quasars: absorption lines

h i


active galactic nuclei

cosmology: observations

einstein a-coefficients


hydrogen-21 centimeter absorption


oh absorption

digital sky survey


S.J. Curran

University of New South Wales (UNSW)

M. T. Whiting

University of New South Wales (UNSW)

Commonwealth Scientific and Industrial Research Organisation (CSIRO)

F. Combes

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

N. Kuno

National Astronomical Observatory of Japan

P. Francis

Australian National University

N. Nakai

University of Tsukuba

J. K. Webb

University of New South Wales (UNSW)

M. T. Murphy

Swinburne University of Technology

University of New South Wales (UNSW)

Tommy Wiklind

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

Monthly Notices of the Royal Astronomical Society

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

Vol. 416 3 2143-2153


Astronomi, astrofysik och kosmologi



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