Issue |
A&A
Volume 409, Number 1, October I 2003
|
|
---|---|---|
Page(s) | 99 - 114 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20031094 | |
Published online | 17 November 2003 |
Dust and nebular emission
I. Models for normal galaxies
1
Scuola Internazionale Superiore di Studi Avanzati, via Beirut 4, 34014 Trieste, Italy
2
INAF, Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
3
INAF, Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
Corresponding author: P. Panuzzo, panuzzo@sissa.it
Received:
14
February
2003
Accepted:
7
July
2003
We present a model for nebular emission in
star forming galaxies, which takes into account the effects of dust
reprocessing. The nebular emissions (continuum emission, 54 H and He recombination lines and 60 nebular lines from UV to IR) have been
computed
with CLOUDY and then included into GRASIL, our spectrophotometric code
specifically developed for dusty galaxies. The interface between
nebular emission and population synthesis is based on a set of
pre-computed region emission models covering a wide range of
physical quantities (metallicity, density, geometry and number of
,
and
ionizing photons). These
quantities are fully adequate to describe the emission properties of
the majority of star-forming and starburst galaxies.
Concerning the extinction properties of normal star
forming galaxies, we are able to
interpret the observed lack of correlation between the attenuation
measured at Hα and in the UV band as a consequence of age
selective extinction. We also find that, for these galaxies with
modest SFR, the ratio FIR/UV provides the best constraints on
the UV attenuation.
The accurate treatment of lines and continuum in dusty galaxies
also allows to deal with different SFR estimators in a consistent way, from the UV to radio wavelengths,
and to discuss the uncertainties arising from the different physical
conditions encountered in star forming galaxies.
We provide our best estimates of SFR/luminosity calibrations, together
with their expected range of variation.
It results that SFR derived through Hα, even when corrected for
extinction using the Balmer decrement, is affected by important uncertainties
due to age selective extinction. Another remarkable result is that SFR
from UV luminosity corrected
by means of the ratio FIR/UV has a small uncertainty. Finally, our model
provides a calibration of SFR from radio luminosity; its value
differs from estimates from other works, but we are
able to reproduce the observed FIR/radio ratio.
These results are relevant to estimates of the contribution of
disk galaxies to the cosmic SFR at
.
Key words: ISM: HII regions / galaxies: ISM / stars: formation / galaxies: evolution
© ESO, 2003
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