Stars, Dust, and the Growth of UV-Selected Sub-L* Galaxies at Redshift
  z~2
  [Abridged] This work concerns very faint (R_lim=28 AB mag; M_(stars, lim) ~
10^8 Msun), UV-selected sub-L* BX galaxies at z~2.3. Stellar masses, dust
content, and dust-corrected SFRs are constrained using broadband SED fitting,
giving insights into the nature of these low-mass systems. First, a correlation
found between rest-frame UV luminosity and galaxy stellar mass suggests that
many sub-L* galaxies at z~2.3 may have approximately constant star formation
histories. A nearly-linear relation between stellar mass and star formation
rate is also found, hinting that the rate at which a sub-L* BX galaxy forms its
stars is directly related to the mass of stars that it has already formed. A
possible explanation is that new gas that falls onto the galaxy's host halo
along with accreting dark matter is the source of fuel for ongoing star
formation. The instantaneous efficiency of star formation is low in this
scenario, of order 1%. The low-mass end of the stellar mass function is steeper
than expected from extrapolations of shallower surveys, resulting in a SMD at
z~2.3 that's ~25% of the present-day value; this value is z~1.5-2x higher than
that given by extrapolations of shallower surveys, suggesting that the build-up
of stellar mass in the universe has proceeded more rapidly than previously
thought. An update to the KDF z~2 UV LF finds a steeper faint-end slope than
previously reported, though not as steep as that found by Reddy & Steidel
(2009). Finally, sub-L* galaxies at z~2 carry very small amounts of dust
compared to their more luminous cousins, so that while only ~20% of 1700A
photons escape from a typical M* galaxy, more than half make it out of an M*+3
one. This paucity of dust highlights the fact that sub-L* galaxies are not
simple scaled copies of their more luminous cousins. It also suggests that
sub-L* are important contributors to keeping the Universe ionized at z~2.
