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Masaru Kajisawa, Takashi Ichikawa, Tomohiro Yoshikawa, Toru Yamada, Masato Onodera, Masayuki Akiyama, Ichi Tanaka, MOIRCS Deep Survey. X. Evolution of Quiescent Galaxies as a Function of Stellar Mass at 0.5 z 2.5, Publications of the Astronomical Society of Japan, Volume 63, Issue sp2, 25 March 2011, Pages S403–S414, https://doi.org/10.1093/pasj/63.sp2.S403
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Abstract
We studied the evolution of quiescent galaxies at 0.5 |$\lt$|z|$\lt$| 2.5 as a function of the stellar mass, using very deep NIR imaging data from the MOIRCS Deep Survey in the GOODS-North region. The deep NIR data allowed us to construct a stellar mass-limited sample of quiescent galaxies down to |$\sim\ $|10|$^{10}\ M_{\odot}$|, even at z|$\sim\ $| 2, for the first time. We selected quiescent galaxies with age / |$\tau$||$\gt$| 6 by performing a SED fitting of the multi broad-band photometry from the |$U$| to Spitzer 5.8|$\ \mu$|m bands with the population synthesis model of Bruzual and Charlot (2003, MNRAS, 344, 1000), where exponentially decaying star-formation histories are assumed. The number density of quiescent galaxies increases by a factor of |$\sim\ $|3 from 1.0 |$\lt$|z|$\lt$| 1.5 to 0.5 |$\lt$|z|$\lt$| 1.0, and by a factor of |$\sim\ $|10 from 1.5 |$\lt$|z|$\lt$| 2.5 to 0.5 |$\lt$|z|$\lt$| 1.0, while that of star-forming galaxies with age / |$\tau$||$\lt$| 4 increases only by factors of |$\sim\ $|2 and |$\sim\ $|3 in the same redshift ranges. At 0.5 |$\lt$|z|$\lt$| 2.5, the low-mass slope of the stellar mass function of quiescent galaxies is |$\alpha$||$\sim\ $| 0–0.6, which is significantly flatter than those of star-forming galaxies (|$\alpha$||$\sim\ $||$-$|1.3–|$-$|1.5). As a result, the fraction of quiescent galaxies in the overall galaxy population increases with stellar mass in the redshift range. The fraction of quiescent galaxies at 10|$^{11}$|–10|$^{11.5}\ M_{\odot}$| increases from |$\sim\ $|20%–30% at z|$\sim\ $| 2 to |$\sim\ $|40%–60% at z|$\sim\ $| 0.75, while that at 10|$^{10}$|–10|$^{10.5}\ M_{\odot}$| increases from |$\lesssim\ $|5% to |$\sim\ $|15% in the same redshift range. These results could suggest that the quenching of star formation had been more effective in more massive galaxies at 1 |$\lesssim\ $|z|$\lesssim\ $| 2. Such a mass-dependent quenching could explain the rapid increase in the number density of |$\sim\ M^*$| galaxies relative to lower-mass galaxies at z|$\gtrsim$| 1–1.5.
