Issue |
A&A
Volume 497, Number 2, April II 2009
|
|
---|---|---|
Page(s) | 351 - 358 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/200811032 | |
Published online | 18 February 2009 |
Ionised carbon and galaxy activity
School of Physics, University of New South Wales, Sydney NSW 2052, Australia e-mail: sjc@phys.unsw.edu.au
Received:
25
September
2008
Accepted:
3
February
2009
We investigate the possibility that the decrease in the
relative luminosity of the 158 μm [C ii] line with the
far-infrared luminosity in extragalactic sources stems from a
stronger contribution from the heated dust emission in the more
distant sources. Because these surveys are flux limited in nature,
the luminosity of the detected objects increases with distance.
However, the [C ii] luminosity does not climb as steeply as that
of the far-infrared, giving the decline in the ratio with LFIR. Investigating this
further, we find that the [C ii] luminosity exhibits similar drops
as measured against the carbon monoxide and radio continuum
luminosities. The former may indicate that at higher luminosities
a larger fraction of the carbon is locked up in the form of
molecules and/or that the CO line radiation also contributes to
the cooling, done mainly by the [C ii] line at low
luminosities. The latter hints at increased activity in these
galaxies at greater distances, so we suggest that, in addition to
an underlying heating of the dust by a stellar population, there
is also heating of the embedded dusty torus by the ultra-violet
emission from the active nucleus, resulting in an excess in the
far-infrared emission from the more luminous objects.
Key words: galaxies: evolution / galaxies: ISM / galaxies: high-redshift / quasars: emission lines / cosmonology: observations
© ESO, 2009
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