Issue |
A&A
Volume 421, Number 1, July I 2004
|
|
---|---|---|
Page(s) | 115 - 127 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20035679 | |
Published online | 11 June 2004 |
Modelling the Spectral Energy Distribution of compact luminous infrared galaxies: Constraints from high frequency radio data
1
Dipartimento di Astronomia, Università degli Studi di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
2
INAF, Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
3
SISSA, Strada Costiera, 34131 Trieste, Italy
4
INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy
Corresponding author: A. Bressan, bressan@pd.astro.it
Received:
14
November
2003
Accepted:
16
March
2004
We have performed 23 GHz VLA observations of 7 compact, luminous
infrared galaxies, selected as showing evidence of starburst
activity. New and published multi-frequency data are combined to
obtain the spectral energy distributions of all 7 galaxies from the
near-infrared to the radio (at 1.4 GHz). These SEDs are compared with
new models, for dust enshrouded galaxies, which account for both
starburst and AGN components.
In all 7 galaxies the starburst provides the dominant contribution to
the infrared luminosity; in 4 sources no contribution from an AGN is
required. Although AGN may contribute up to 50 percent of the total
far-infrared emission, the starbursts always dominate in the
radio. The SEDs of most of our sources are best fit with a very high
optical depth of ~50 at .
The scatter in the far-infrared/radio correlation, found among
luminous IRAS sources, is due mainly to the different evolutionary
status of their starburst components. The short time-scale of the
star formation process amplifies the delay between the far-infrared
and radio emission. This becomes more evident at low radio frequencies
(below about 1 GHz) where synchrotron radiation is the dominant
process. In the far-infrared (at wavelengths shorter than 100 μm)
an additional source of scatter is provided by AGN, when present. AGN
may be detected in the near-infrared by the absence of the knee,
typical of stellar photospheres. However, near-infrared data alone
cannot constrain the level at which AGN contribute because the
interpretation of their observed properties, in this wave-band,
depends strongly on model parameters.
Key words: ISM: dust, extinction / galaxies: stellar content / infrared: galaxies / radio continuum: galaxies
© ESO, 2004
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