Host galaxies of high-redshift extremely red and obscured quasars
  We present Hubble Space Telescope 1.4-1.6 micron images of the hosts of ten
extremely red quasars (ERQs) and six type 2 quasar candidates at z=2-3. ERQs,
whose bolometric luminosities range between 10^47 and 10^48 erg/sec, show
spectroscopic signs of powerful ionized winds, whereas type 2 quasar candidates
are less luminous and show only mild outflows. After performing careful
subtraction of the quasar light, we clearly detect almost all host galaxies.
The median rest-frame B-band luminosity of the ERQ hosts in our sample is
10^11.2 L_Sun, or 4 L* at this redshift. Two of the ten hosts of ERQs are in
ongoing mergers. The hosts of the type 2 quasar candidates are 0.6 dex less
luminous, with 2/6 in likely ongoing mergers. Intriguingly, despite some signs
of interaction and presence of low-mass companions, our objects do not show
nearly as much major merger activity as do high-redshift radio-loud galaxies
and quasars. In the absence of an overt connection to major ongoing gas-rich
merger activity, our observations are consistent with a model in which the
near-Eddington accretion and strong feedback of ERQs are associated with
relatively late stages of mergers resulting in early-type remnants. These
results are in some tension with theoretical expectations of galaxy formation
models, in which rapid black hole growth occurs within a short time of a major
merger. Type 2 quasar candidates are less luminous, so they may instead be
powered by internal galactic processes.
