Issue |
A&A
Volume 397, Number 3, January III 2003
|
|
---|---|---|
Page(s) | 871 - 881 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20021572 | |
Published online | 21 January 2003 |
[C II] emission and star formation in late-type galaxies*
II. A model
1
Ritter Astrophysical Research Center, The University of Toledo, Toledo, OH 43606, USA
2
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany e-mail: dpierini@mpe.mpg.de
3
ISO Data Centre, Astrophysics Division, ESA Space Science Dept., PO Box 50727 Madrid, Spain e-mail: kleech@iso.vilspa.esa.es
4
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany e-mail: Heinrich.Voelk@mpi-hd.mpg.de
Corresponding author: D. Pierini, dpierini@mpe.mpg.de
Received:
16
August
2001
Accepted:
29
October
2002
We study the relationship between gas cooling via the [C II]
() line emission and dust cooling
via the far-IR continuum emission on the global scale of a galaxy
in normal (i.e. non-AGN dominated and non-starburst) late-type systems.
It is known that the luminosity ratio of total gas and dust cooling,
, shows a non-linear behaviour with
the equivalent width of the
(
)
line emission, the ratio decreasing in galaxies of lower massive
star-formation activity.
This result holds despite the fact that known individual Galactic
and extragalactic sources of the [C II] line emission show
different [C II] line-to-far-IR continuum emission ratios.
This non-linear behaviour is reproduced by a simple quantitative theoretical model
of gas and dust heating from different stellar populations, assuming that
the photoelectric effect on dust, induced by far-UV photons,
is the dominant mechanism of gas heating in the general diffuse
interstellar medium of the galaxies under investigation.
According to the model, the global
provides a direct measure of the fractional amount of non-ionizing UV
light in the interstellar radiation field and not of the efficiency
of the photoelectric heating.
The theory also defines a method to constrain the stellar initial mass
function from measurements of
and
.
A sample of 20 Virgo cluster galaxies observed in the [C II] line
with the Long Wavelength Spectrometer on board the Infrared Space
Observatory is used to illustrate the model.
The limited statistics and the necessary assumptions behind
the determination of the global [C II] luminosities from the spatially
limited data do not allow us to establish definitive conclusions
but data-sets available in the future will allow tests of both
the reliability of the assumptions behind our model and the statistical
significance of our results.
Key words: galaxies: ISM / galaxies: spiral / galaxies: stellar content / infrared: galaxies / infrared: ISM / ISM: lines and bands
© ESO, 2003
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