Dust Obscuration and Metallicity at High Redshift: New Inferences from
  UV, H-alpha, and 8 Micron Observations of z~2 Star-Forming Galaxies
  We use a sample of 90 spectroscopically-confirmed Lyman Break Galaxies with
H-alpha and 24 micron observations to constrain the relationship between
rest-frame 8 micron luminosity, L(8), and star formation rate (SFR) for L*
galaxies at z~2. We find a tight correlation with 0.24 dex scatter between L8
and L(Ha)/SFR for z~2 galaxies with L(IR)~10^10 - 10^12 Lsun. Employing this
relationship with a larger sample of 392 galaxies with spectroscopic redshifts,
we find that the UV slope can be used to recover the dust attenuation of the
vast majority of L* galaxies at z~2 to within 0.4 dex scatter using the local
correlation. Separately, young galaxies with ages <100 Myr appear to follow an
extinction curve that is steeper than the one found for local starburst
galaxies. Therefore, such young galaxies may be significantly less dusty than
inferred previously. Our results provide the first direct evidence, independent
of the UV slope, for a correlation between UV and bolometric luminosity at high
redshift, in the sense that UV-faint galaxies are also on average less infrared
and less bolometrically-luminous than their UV-bright counterparts. Further, as
the SFR increases, the UV luminosity reaches a maximum value corresponding to
L* at z~2, implying that dust obscuration may be largely responsible for
modulating the bright-end of the UV luminosity function. L* galaxies at z~2,
while at least an order of magnitude more bolometrically-luminous, exhibit
ratios of metals-to-dust that are similar to those of local starbursts. This
result is expected if high-redshift galaxies are forming their stars in a less
metal-rich environment compared to local galaxies of the same luminosity, thus
naturally leading to a redshift evolution in both the luminosity-metallicity
and luminosity-obscuration relations. [Abridged]
