The warm and cold far-infrared/radio correlations
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. Cuţitul de Argint 5, Bucharest, Romania
Corresponding author: D. Pierini, firstname.lastname@example.org
Accepted: 29 July 2003
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 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 (). 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 (). For the cold FIR/radio correlation we found a slightly non-linear () 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
Based on observations with the Infrared Space Observatory (ISO), an ESA project with instruments funded by ESA member States (especially the PI countries: France, Germany, The Netherlands, and the UK) and with the participation of ISAS and NASA.
© ESO, 2003