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.
Back to Projects.
