On the Impact of Inclination-Dependent Attenuation on Derived Star Formation Histories: Results from Disk Galaxies in the Great Observatories Origins Deep Survey Fields

We develop and implement an inclination-dependent attenuation prescription for spectral energy distribution (SED) fitting and study its impact on derived star-formation histories. We apply our prescription within the SED fitting code Lightning to a clean sample of 82, z=0.21-1.35 disk-dominated galaxies in the Great Observatories Origins Deep Survey North and South fields. To compare our inclination-dependent attenuation prescription with more traditional fitting prescriptions, we also fit the SEDs with the inclination-independent Calzetti et al. (2000) attenuation curve. From this comparison, we find that fits to a subset of 58, z < 0.7 galaxies in our sample, utilizing the Calzetti et al. (2000) prescription, recover similar trends with inclination as the inclination-dependent fits for the far-UV-band attenuation and recent star-formation rates. However, we find a difference between prescriptions in the optical attenuation (AV) that is strongly correlated with inclination (p-value < 10^-11). For more face-on galaxies, with i < 50 deg, (edge-on, i = 90 deg), the average derived AV is 0.31 +\- 0.11 magnitudes lower (0.56 +\- 0.16 magnitudes higher) for the inclination-dependent model compared to traditional methods. Further, the ratio of stellar masses between prescriptions also has a significant (p-value < 10^-2) trend with inclination. For i = 0-65 deg, stellar masses are systematically consistent between fits, with log(Mstar_inc/Mstar_Calzetti) = -0.05 +/- 0.03 dex and scatter of 0.11 dex. However, for i = 80-90 deg, derived stellar masses are lower for the Calzetti et al. (2000) fits by an average factor of 0.17 +\- 0.03 dex and scatter of 0.13 dex. Therefore, these results suggest that SED fitting assuming the Calzetti et al. (2000) attenuation law potentially underestimates stellar masses in highly inclined disk-dominated galaxies.
Comment: 38 pages, 22 figures. 30 page body and 8 page appendix. Updated with published version