The Strength of the 2175\AA\ Feature in the Attenuation Curves of Galaxies at 0.1<z<3

TL;DR

This study updates the MAGPHYS spectral modeling code to include the 2175Å absorption feature, enabling analysis of dust attenuation curves in thousands of galaxies across a range of redshifts, revealing dependencies on galaxy properties.

Contribution

The paper introduces an updated MAGPHYS code that models the 2175Å dust absorption feature, allowing for detailed analysis of dust attenuation in galaxies from z=0.1 to 3.

Findings

A 2175Å feature of about one-third Milky Way strength is needed in models.

Attenuation curve slopes correlate with star formation rate and dust attenuation.

No significant trend found in 2175Å feature strength across galaxy properties.

Abstract

We update the spectral modeling code MAGPHYS to include a 2175\AA\ absorption feature in its UV-to-near-IR dust attenuation prescription. This allows us to determine the strength of this feature and the shape of the dust attenuation curve in ~5000 star-forming galaxies at 0.1<z<3 in the COSMOS field. We find that a 2175\AA\ absorption feature of ~1/3 the strength of that in the Milky Way is required for models to minimize residuals. We characterize the total effective dust attenuation curves as a function of several galaxy properties and find that the UV slopes of the attenuation curve for COSMOS galaxies show a strong dependence with star formation rate (SFR) and total dust attenuation ($A_V$), such that galaxies with higher SFR and $A_V$ have shallower curves and vice versa. These results are consistent with expectations from radiative transfer that attenuation curves become shallower as the effective dust optical depth increases. We do not find significant trends in the strength of the 2175\AA\ absorption feature as a function of galaxy properties, but this may result from the high uncertainties associated with this measurement. The updated code is publicly available online.