Using observations from the FourStar Galaxy Evolution Survey ( ZFOURGE ) , we obtain the deepest measurements to date of the galaxy stellar mass function at 0.2 < z < 3 .
ZFOURGE provides well-constrained photometric redshifts made possible through deep medium-bandwidth imaging at 1–2 \mu m. We combine this with HST imaging from the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey ( CANDELS ) , allowing for the efficient selection of both blue and red galaxies down to stellar masses \sim 10 ^ { 9.5 } M _ { \odot } at z \sim 2.5 .
The total surveyed area is 316 arcmin ^ { 2 } distributed over three independent fields .
We supplement these data with the wider and shallower NEWFIRM Medium-Band Survey ( NMBS ) to provide stronger constraints at high masses .
Several studies at z \leq 1.5 have revealed a steepening of the slope at the low-mass end of the stellar mass function ( SMF ) , leading to an upturn at masses < 10 ^ { 10 } M _ { \odot } that is not well-described by a standard single-Schechter function .
We find evidence that this feature extends to at least z \sim 2 , and that it can be found in both the star-forming and quiescent populations individually .
The characteristic mass ( M ^ { * } ) and slope at the lowest masses ( \alpha ) of a double-Schechter function fit to the SMF stay roughly constant at Log ( M/M _ { \odot } ) \sim 10.65 and \sim - 1.5 respectively .
The SMF of star-forming galaxies has evolved primarily in normalization , while the change in shape is relatively minor .
Our data allow us for the first time to observe a rapid buildup at the low-mass end of the quiescent SMF .
Since z = 2.5 , the total stellar mass density of quiescent galaxies ( down to 10 ^ { 9 } M _ { \odot } ) has increased by a factor of \sim 12 whereas the mass density of star-forming galaxies only increases by a factor of \sim 2.2 .