Astron. Astrophys. 363, 917-925 (2000)

6. Luminosities

The IR luminosities have been determined by integrating (1) the modified Planck curves between 8 µm and 1000 µm, and - for comparison - (2) the measured fluxes in the three rectangular bandpasses. The latter values are about 10% lower, as expected due to the missing fraction at longer wavelengths: beyond 230 , the flux density is extrapolated by the modified Planck curve. Columns (12) and (13) of Table 1 list the luminosity ratio of cold and warm modified Planckian and the total FIR luminosity within the chosen aperture.

The FIR luminosity integrated over all knots yields , which is about 12% of the FIR luminosity estimated by Haas et al. (1998) for the whole galaxy. However, this is only a lower limit, as the apertures cut off some of the flux of each knot. An upper limit can be estimated as follows: the rings comprise about 30% of the total luminosity of the whole galaxy, whereby 5% may be attributed to the disk. The luminosity of the knots is therefore less than 25% of that of the whole galaxy.

© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000
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