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Paper: A Steep Faint-End Slope of the UV Luminosity Function at z∼2–3: Implications for the Missing Stellar Mass Problem
Volume: 419, Galaxy Evolution: Emerging Insights and Future Challenges
Page: 313
Authors: Reddy, N. A.
Abstract: We use the deep ground-based optical photometry of the Lyman Break Galaxy (LBG) Survey to derive robust measurements of the faint-end slope (α) of the UV luminosity function (LF) at redshifts 1.9 ≤ z ≤ 3.4. Our sample includes >2000 spectroscopic redshifts and ≈ 31000 LBGs in 31 spatially-independent fields over a total area of 3261 arcmin2. These data allow us to select galaxies to 0.07L* and 0.10L* at z∼2 and z∼3, respectively. A maximum-likelihood analysis indicates steep values of α(z=2) = −1.73±0.07 and α(z=3) = −1.73±0.13. This result is robust to luminosity-dependent systematics in the Lyα equivalent width and reddening distributions, is similar to the steep values advocated at z ≥ 4, and implies that ≈93% of the unobscured UV luminosity density at z∼2–3 arises from sub-L* galaxies. We find a factor of 8–9 increase in the star formation rate density between z∼6 and z∼2, due to both a brightening of L* and an increasing dust correction proceeding to lower redshifts. Combining the UV LF with stellar mass estimates suggests a relatively steep low mass slope of the stellar mass function at high redshift. We show that the previously observed discrepancy between the integral of the star formation history and stellar mass density measurements at z∼2 may be reconciled by accounting for the lower attenuation of UV-faint galaxies relative to their brighter counterparts, the stellar mass contributed by UV-faint galaxies, and subjecting the stellar mass and star formation rate density estimates to the same limiting luminosity.
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