Evidence for a wide range of UV obscuration in z ~ 2 dusty galaxies from
  the GOODS-Herschel survey
  Dusty galaxies at z ~ 2 span a wide range of relative brightness between
rest-frame mid-infrared (8um) and ultraviolet wavelengths. We attempt to
determine the physical mechanism responsible for this diversity. Dust-obscured
galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios > 1000,
might be abnormally bright in the mid-IR, perhaps due to prominent AGN and/or
PAH emission, or abnormally faint in the UV. We use far-infrared data from the
GOODS-Herschel survey to show that most DOGs with 10^12 L_Sun < L_IR < 10^13
L_Sun are not abnormally bright in the mid-IR when compared to other dusty
galaxies with similar IR (8--1000um) luminosities. We observe a relation
between the median IR to UV luminosity ratios and the median UV continuum
power-law indices for these galaxies, and we find that only 24% have specific
star formation rates which indicate the dominance of compact star-forming
regions. This circumstantial evidence supports the idea that the UV- and
IR-emitting regions in these galaxies are spatially coincident, which implies a
connection between the abnormal UV faintness of DOGs and dust obscuration. We
conclude that the range in rest-frame mid-IR to UV flux density ratios spanned
by dusty galaxies at z ~ 2 is due to differing amounts of UV obscuration. Of
galaxies with these IR luminosities, DOGs are the most obscured. We attribute
differences in UV obscuration to either: 1) differences in the degree of
alignment between the spatial distributions of dust and massive stars, or 2)
differences in the total dust content.
