ner_tags: O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O B-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O B-Citation O O O O O O O O O O O O B-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation O O O O O O O O O O O O B-Citation O O O O O O O O B-Wavelength O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O B-Citation O O O O B-Wavelength O O O O O O O O O O O O O O O O B-CelestialObject O B-Citation I-Citation I-Citation I-Citation O O O B-CelestialObject I-CelestialObject B-Citation I-Citation I-Citation I-Citation O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O B-Citation O O O O O O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O
tokens: which both β and IRX have been measured (Capak et al. 2015 ), but the galaxies with from Capak et al. ( 2015 ) and the galaxy presented by Watson et al. ( 2015 ) lie outside the region spanned by the simulated galaxies. Because our simulations and theirs cover disjoint regions of parameter space in terms of redshift and mass, it is not possible to make detailed comparisons between our results and theirs. However, their results highlight the potential importance of dust destruction for accurately predicting the UV properties of simulated galaxies and provide motivation for future studies that include more complex treatments of dust production, growth, and destruction. 9. Implications for Observations Our simulation results suggest that there is not a tight relation between IRX and β that applies to all galaxies at all redshifts. The simulated galaxies tend to lie near the M99 relation, which was determined based on observations of galaxies in the local universe. However, during merger-induced starbursts, even the galaxies can depart significantly from the relation: because IRX increases significantly but β is almost unaffected, the merger-induced starbursts, such as that shown in Figure 3 , tend to lie above the M99 relation. The simulations—of both disk galaxies and mergers—deviate more significantly from the M99 relation: even when they are not undergoing starbursts, they tend to lie above the relation. These results are consistent with observational works that have demonstrated that some classes of galaxies deviate significantly from the M99 relation. As already discussed above, observed DSFGs tend to lie above the M99 relation and do not exhibit any relationship between IRX and β (e.g., Bell et al. 2002 ; Goldader et al. 2002 ; Howell et al. 2010 ; Casey et al. 2014 ). Conversely, some galaxies lie significantly below the M99 relation (i.e., have lower IRX than expected from the relation given their β ). This was demonstrated for the lensed galaxies cB58 at (Pettini et al. 2000 ) and the Cosmic Eye (Smail et al. 2007 ) at . Similarly, Reddy et al. ( 2012 ) found that young systems (age Myr) at lie below the M99 relation. Moreover, we have demonstrated that the dust composition—specifically the strength of the 2175 Å feature—can have a very dramatic effect on the UV slope. Consequently, extrapolation of the locally calibrated relation to regimes for which it is not observationally constrained may be problematic if, e.g., the dust composition of high-redshift galaxies is significantly different from that of galaxies. How the strength of the UV bump varies with galaxy properties and redshift is still poorly understood, but there are some useful observational constraints. The commonly employed Calzetti et al. ( 1994 ) attenuation law, which was defined based on observations of local-universe starburst galaxies, does not exhibit a UV bump. Based on a study of ∼10,000 star-forming galaxies, Battisti et al. ( 2016 ) derived an average attenuation