THE NUMBER DENSITY OF QUIESCENT COMPACT GALAXIES AT INTERMEDIATE REDSHIFT

Abstract

Massive compact systems at 0.2<z<0.6 are the missing link between the\npredominantly compact population of massive quiescent galaxies at high redshift\nand their analogs and relics in the local volume. The evolution in number\ndensity of these extreme objects over cosmic time is the crucial constraining\nfactor for the models of massive galaxy assembly. We select a large sample of\n~200 intermediate-redshift massive compacts from the BOSS spectroscopic dataset\nby identifying point-like SDSS photometric sources with spectroscopic\nsignatures of evolved redshifted galaxies. A subset of our targets have\npublicly available high-resolution ground-based images that we use to augment\nthe dynamical and stellar population properties of these systems by their\nstructural parameters. We confirm that all BOSS compact candidates are as\ncompact as their high-redshift massive counterparts and less than half the size\nof similarly massive systems at z~0. We use the completeness-corrected numbers\nof BOSS compacts to compute lower limits on their number densities in narrow\nredshift bins spanning the range of our sample. The abundance of extremely\ndense quiescent galaxies at 0.2<z<0.6 is in excellent agreement with the number\ndensities of these systems at high redshift. Our lower limits support the\nmodels of massive galaxy assembly through a series of minor mergers over the\nredshift range 0<z<2.\n