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Host galaxies of high-redshift extremely red and obscured quasars

Author(s): Zakamska, Nadia L; Sun, Ai-Lei; Strauss, Michael A; Alexandroff, Rachael M; Brandt, WN; et al

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Abstract: 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.
Publication Date: 27-Jul-2019
Electronic Publication Date: Oct-2019
Citation: Zakamska, Nadia L, Sun, Ai-Lei, Strauss, Michael A, Alexandroff, Rachael M, Brandt, WN, Chiaberge, Marco, Greene, Jenny E, Hamann, Fred, Liu, Guilin, Perrotta, Serena, Ross, Nicholas P, Wylezalek, Dominika. (2019). Host galaxies of high-redshift extremely red and obscured quasars. \mnras, 489 (497 - 516. doi:10.1093/mnras/stz2071
DOI: doi:10.1093/mnras/stz2071
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Pages: 497 - 516
Type of Material: Journal Article
Journal/Proceeding Title: Monthly Notices of the Royal Astronomical Society
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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