IRX–β RELATION OF STAR-FORMING REGIONS IN NGC 628 BASED ON INTEGRAL FIELD SPECTROSCOPY

Abstract

It has been found that the infrared-to-ultraviolet luminosity ratio (IRX) and ultraviolet spectral slope ( β ) have a tight correlation in starburst galaxies, while in normal galaxies the relation is deviated and has a much larger scatter. Star formation regions are much simpler in both morphology and physical properties than galaxies, so their photometric and spectroscopic properties are more easily and accurately determined. We have used the integral field spectroscopy and multiband photometric images to study the IRX– β relation of H ii regions in a nearby galaxy, NGC 628. There are obvious correlations between the D n (4000), stellar population age, star formation rate, especially H α equivalent width EW(H α ), and deviation distance d p from the starburst IRX– β relation. However, there is little correlation between the Balmer decrement, metallicity, and d p . It is much more complicated than expected, so that we cannot introduce a single second parameter to describe the scatter and deviation of the H ii region IRX– β relation.