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