Astronomy and Astrophysics, volume 285, 51-68 (1994/5-1)
Global properties of dwarf galaxies II. Colours and luminosities.
MELISSE J.P.M. and ISRAEL F.P.
Abstract (from CDS):
We have used a previously determined sample of 278 dwarf galaxies for most of which B magnitudes, optical colours, HI fluxes and IRAS flux-densities are known, in order to derive luminosities, colours and surface brightnesses. Dwarf galaxy properties are compared to those of a control sample of 228 larger spiral galaxies. The dwarf galaxies have on average higher 60/100µm flux ratios and lower 12/25µm flux ratios than the spiral galaxies, indicating that the contribution of `cirrus' to the infrared emission from dwarf galaxies is relatively insignificant. In the dwarf galaxies, the 60/100µm flux ratio increases with increasing optical blueness; spiral galaxies show the opposite. Dwarf galaxies with a low optical surface brightness have low 100µm/HI ratios, but the converse is not true. Galaxies with high 100µm/HI ratios (indicative of high dust-to-gas ratios) also have high FIR/B ratios as well as high 60/100µm flux-density ratios. Although this is true for both spiral and dwarf galaxies, at given 100µm/HI ratios the dwarf galaxies have both a lower FIR/B ratio and a higher 60/100µm flux-density ratio. This result is of importance in the interpretation of FIR/B - 60/100µm diagrams in terms of star formation activity.