High Mass Star Formation Along the Hubble Sequence
- Devereux, Hameed

Far infrared fluxes have been extracted from the IRAS database for galaxies in the Nearby Galaxies Catalog (Devereux & Hameed 1997, AJ 113, 599). The IRAS data are used to determine the Hubble type dependence of the far infrared luminosity and the L(FIR)/L(Blue) ratio. Adopting the far infrared luminosity as a measure of the massive star formation rate, one finds that the IRAS data reveal a previously unsuspected population of early type (Sa-Sab) spirals with massive star formation rates that rival the most prodisously star forming Sc galaxies. Thus, the IRAS data do not support the distinction between the global star forming capabilities of early and late type spirals that has been reported previously in the published literature.

Fractional 60 micron luminosity functions for 1874 galaxies of different Hubble type. The percentage of galaxies with 60 micron luminosities greater than L(lim) is plotted on the y-axis and the value of L(lim) is plotted on the x-axis. The luminosity functions are similar for spiral galaxies of types Sa-Scd, whereas the median 60 micron luminosity for the very early, S0-S0/a, and very late, Sd-Sdm, types is about one order of magnitude lower than the other spirals (Sa-Scd). Ellipticals and Magellanic Irregular galaxies have median 60 micron luminosities another order of magnitude lower.

Histograms illustrating the Hubble type dependence of the L(40-120micron)/ L(Blue) luminosity ratio for 1462 galaxies. The hatched hitograms identify far infrared detections, the unshaded histograms identify upper limits to the far infrared flux. The verticle bar identifies the median of the distribution. Again the median for the ratios seems to be independent of the Hubble type for spirals of types Sa-Scd. Solid circles identify the luminous Sa-Sab galaxies.

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