EDP Sciences
Free access
Issue
A&A
Volume 409, Number 3, October III 2003
Page(s) 907 - 916
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20031220


A&A 409, 907-916 (2003)
DOI: 10.1051/0004-6361:20031220

The far-infrared/radio correlation in the ISO era

The warm and cold far-infrared/radio correlations
D. Pierini1, C. C. Popescu2, 3, R. J. Tuffs2 and H. J. Völk2

1  Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr., 85748 Garching, Germany
2  Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
    e-mail: [Cristina.Popescu;Richard.Tuffs;Heinrich.Voelk]@mpi-hd.mpg.de
3  Research Associate, The Astronomical Institute of the Romanian Academy, Str. Cutitul de Argint 5, Bucharest, Romania

(Received 19 March 2003 / Accepted 29 July 2003)

Abstract
We present the correlation between the far-infrared (FIR) and radio emissions from a composite sample of 72 nearby normal galaxies observed with the ISOPHOT instrument on board the Infrared Space Observatory. The galaxies in the sample have measurements at three FIR wavelengths (60, 100 and 170  ${\mu}$m), which allowed a direct determination of the warm and cold FIR emission components. This is the first time that the correlation has been established for the total FIR luminosity, of which most is carried by the cold dust component predominantly emitting longwards of the spectral coverage of IRAS. The slope of this correlation is slightly non-linear ( $1.10\pm 0.03$). Separate correlations between the warm and cold FIR emission components and the radio emission have also been derived. The slope of the warm FIR/radio correlation was found to be linear ( $1.03 \pm 0.03$). For the cold FIR/radio correlation we found a slightly non-linear ( $1.13 \pm 0.04$) slope. We qualitatively interpret the correlations in terms of star formation rate and find that both the FIR and radio emissions may be consistent with a non-linear dependence on star formation rate for galaxies not undergoing starburst activity.


Key words: galaxies: spiral -- galaxies: stellar content -- galaxies: ISM -- infrared: galaxies -- radio continuum: galaxies

Offprint request: D. Pierini, dpierini@mpe.mpg.de

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