6. Reddening and extinction
The top panel in Fig. 5 contains a histogram of the reddenings towards the HII regions in our sample, corrected for the galactic contribution (Burstein & Heiles 1984). The middle panel contains a histogram for the sample of McGaugh (1994), while the bottom panel shows both samples combined. It is clear that the extinction in HII regions is low with mag. For normal HSB galaxies extinction values are usually found to be up to a factor 6 larger (see e.g. Fig. 7 in Zaritsky et al. 1994). The conclusion that can be drawn from this, is that the reddening towards these HII regions is low, but at some sites some dust is present.
In the lowest abundance HII regions star formation is apparently able to proceed without much dust. These low reddenings also confirm that dust is not the cause of the low surface brightness of LSB galaxies.
© European Southern Observatory (ESO) 1998
Online publication: June 18, 1998