Host galaxies of high-redshift extremely red and obscured quasars

Nadia L. Zakamska, Ai Lei Sun, Michael A. Strauss, Rachael M. Alexandroff, W. N. Brandt, Marco Chiaberge, Jenny E. Greene, Fred Hamann, Guilin Liu, Serena Perrotta, Nicholas P. Ross, Dominika Wylezalek

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


We present Hubble Space Telescope 1.4-1.6 μm images of the hosts of 10 extremely red quasars (ERQs) and six type 2 quasar candidates at z = 2-3. ERQs, whose bolometric luminosities range between 1047 and 1048 erg s−1, 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 1011.2 L, or ∼4L at this redshift. Two of the 10 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.

Original languageEnglish (US)
Pages (from-to)497-516
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Oct 11 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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