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

Abstract

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, $E(B-V{)}_{\mathrm{star}}$, using the technique developed by Li et al.(2020), as well as the gas attenuation, $E(B-V{)}_{\mathrm{gas}}$, from the Balmer decrement. We then examine the correlation of $E(B-V{)}_{\mathrm{star}}$, $E(B-V{)}_{\mathrm{gas}}$, $E(B-V{)}_{\mathrm{gas}}-E(B-V{)}_{\mathrm{star}}$ and $E(B-V{)}_{\mathrm{star}}/E(B-V{)}_{\mathrm{gas}}$ with 16 regional/global properties, and for regions with different $\mathrm{H}\hat{\mathrm{I}}\pm$ surface brightnesses ($\hat{I}{\pounds }_{\mathrm{H}\hat{\mathrm{I}}\pm }$). We find a stronger correlation between $E(B-V{)}_{\mathrm{star}}$ and $E(B-V{)}_{\mathrm{gas}}$ in regions of higher $\hat{I}{\pounds }_{\mathrm{H}\hat{\mathrm{I}}\pm }$. Luminosity-weighted age ($t_L$) is found to be the property that is the most strongly correlated with $E(B-V{)}_{\mathrm{star}}$, and consequently with $E(B-V{)}_{\mathrm{gas}}-E(B-V{)}_{\mathrm{star}}$ and $E(B-V{)}_{\mathrm{star}}/E(B-V{)}_{\mathrm{gas}}$. At fixed $\hat{I}{\pounds }_{\mathrm{H}\hat{\mathrm{I}}\pm }$, ${\log }_{10}{t}_L$ is linearly and negatively correlated with $E(B-V{)}_{\mathrm{star}}/E(B-V{)}_{\mathrm{gas}}$ 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).

accepted by ApJ