Abstract
ABSTRACT Dust attenuation in star-forming spiral galaxies affects stars and gas in different ways due to local variations in dust geometry. We present spatially resolved measurements of dust attenuation for a sample of 232 such star-forming spiral galaxies, derived from spectra acquired by the SDSS-IV MaNGA survey. The dust attenuation affecting the stellar populations of these galaxies (obtained using full spectrum stellar population fitting methods) is compared with the dust attenuation in the gas (derived from the Balmer decrement). Both of these attenuation measures increase for local regions of galaxies with higher star formation rates; the dust attenuation affecting the stellar populations increases more so than the dust attenuation in the gas, causing the ratio of the dust attenuation affecting the stellar populations to the dust attenuation in the gas to decrease for local regions of galaxies with higher star formation rate densities. No systematic difference is discernible in any of these dust attenuation quantities between the spiral arm and interarm regions of the galaxies. While both the dust attenuation in the gas and the dust attenuation affecting the stellar populations decrease with galactocentric radius, the ratio of the two quantities does not vary with radius. This ratio does, however, decrease systematically as the stellar mass of the galaxy increases. Analysis of the radial profiles of the two dust attenuation measures suggests that there is a disproportionately high concentration of birth clouds (incorporating gas, young stars, and clumpy dust) nearer to the centres of star-forming spiral galaxies.
Highlights
Properties of galaxies such as gas metallicities and star formation rates (SFRs) are derived from nebular emission lines produced as a result of gas heated by star-forming (SF) regions
No statistically significant dependence on global sSFRHα relative to the star-forming main sequence (SFMS) is detected for the ratio of these two quantities; Table 1 shows that the mean values for the the global light-weighted AV, stars/AV, gas ratio remain roughly constant at ∼0.35
We investigate how the average dust attenuation quantities depend on galaxy stellar mass
Summary
Properties of galaxies such as gas metallicities and star formation rates (SFRs) are derived from nebular emission lines produced as a result of gas heated by star-forming (SF) regions. Such observations provide spatially resolved measurements for each of the dust attenuation derived from the gas, the dust attenuation affecting the stellar populations, and the excess between the former quantity and the latter This final metric is perhaps a more physically meaningful property than the ratio between the two dust attenuation measures determined by previous studies, since it quantifies the excess dust attenuation close to the plane of the galaxy. But complementary, methods are used: first by using the Balmer decrement as a diagnostic for the dust attenuation in the gas, and second by using full-spectrum stellar population fitting methods to measure the dust attenuation affecting the stellar populations in the same galaxies We will use this analysis to propose a new geometry for the dust distribution in SF spiral galaxies, as well as putting better constraints on the difference between the optical depth of the Balmer emission lines Hα and Hβ and that affecting the stellar continuum.
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