Estimating dust attenuation from galactic spectra. II. Stellar and gas attenuation in star-forming and diffuse ionized gas regions in MaNGA

We investigate the dust attenuation in both stellar populations and ionized gas in kpc-scale regions in nearby galaxies, using integral field spectroscopy data from MaNGA MPL-9. We identify star-forming (HII) and diffuse ionized gas (DIG) regions from MaNGA datacubes. From the stacked spectrum of each region, we measure the stellar attenuation, $E(B-V{)}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{r}}$, using the technique developed by Li et al.(2020), as well as the gas attenuation, $E(B-V){\rm gas}$,fromtheBalmerdecrement\mathrm{.}Wethenexaminethecorrelationof$E(B-V){\rm star}$,$E(B-V){\rm gas}$,$E(B-V){\rm gas}-E(B-V){\rm star}$and$E(B-V){\rm star}/E(B-V){\rm gas}$ with 16 regional/global properties, and for regions with different $\mathrm{H}\alpha$ surface brightnesses (${\mathrm{\Sigma }}_{\mathrm{H}\alpha }$). We find a stronger correlation between $E(B-V){\rm star}$and$E(B-V){\rm gas}$inregionsofhigher$\Sigma{\rm H\alpha}$. Luminosity-weighted age ($t_L$) is found to be the property that is the most strongly correlated with $E(B-V{)}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{r}}$, and consequently with $E(B-V{)}_{\mathrm{g}\mathrm{a}\mathrm{s}}-E(B-V{)}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{r}}$ and $E(B-V{)}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{r}}\mathrm{/}E(B-V{)}_{\mathrm{g}\mathrm{a}\mathrm{s}}$. At fixed ${\mathrm{\Sigma }}_{\mathrm{H}\alpha }$, ${\log }_{10}{t}_L$ is linearly and negatively correlated with $E(B-V{)}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{r}}\mathrm{/}E(B-V{)}_{\mathrm{g}\mathrm{a}\mathrm{s}}$ at all ages. Gas-phase metallicity and ionization level are important for the attenuation in the gas. Our results indicate that the ionizing source for DIG regions is likely distributed in the outer-skirt of galaxies, while for HII regions our results can be well explained by the two-component dust model of Charlot & Fall (2000).