Evidence for enhanced star formation in iras-detected markarian galaxies |
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| Authors: | G T Petrov |
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| Institution: | (1) Department of Astronomy and National Astronomical Observatory, Bulgarian Academy of Science, Sofia, Bulgaria |
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| Abstract: | The IR emission of 640 Markarian galaxies (MrkG), included in the IRAS Survey, is considered as an evidence for enhanced star formation rate (SFR) in these objects. About 73% of the MrkG have high far-infrared luminosities (ca. 10E + 44 erg s–1) in 1–500 mcm IR spectral band. The distribution of log(f
60/f
100), peaked at about 45 K, shows that IRAS MrkGs have a tendency to extend the relationf
60/f
100 vsL
ir/L
bifor  normal S glaxies. They emit up to hundred times more IR energy in 40–120 mcm band than in optics. The mean ratio log  L
ir/L
b for 621 IRAS MrkG with known redshifts is 2.2.It is suggested that there are two IR emitting components in the IRAS MrkG - a warm one connected with the UV-fluxes of the newborn massive stars, re-radiated by dust, and a cool one, originated from the dust in galactic disks and heated by the general interstellar radiation field. The warm IR luminosities and warm IR fractions are determined on the basis of IR colour-colour diagrams (25/12),(60/25), and(100/60). The mean warm IR fraction for all Mrk IRAS detected galaxies with well-defined IR fluxes is 0.83 when the grain mass absorption coefficient model withn = 0.0 is used. The dust mass responsible for the IR flux at 60 mcm is derived to be about 10E + 5M
 , assuming the dust clouds are optically thin, and using the dust temperatureT
d 46 K (deduced from thef(60)/f(100) ratio). There is a relation betweenL
irandL
blwhich points out that the most IRAS MrkG have rather enhanced SFR. |
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