High-redshift Extremely Red Quasars in X-Rays

Media type: E-Article
Title: High-redshift Extremely Red Quasars in X-Rays
Contributor: Goulding, Andy D.; Zakamska, Nadia L.; Alexandroff, Rachael M.; Assef, Roberto J.; Banerji, Manda; Hamann, Fred; Wylezalek, Dominika; Brandt, William N.; Greene, Jenny E.; Lansbury, George B.; Pâris, Isabelle; Richards, Gordon; Stern, Daniel; Strauss, Michael A.
imprint: American Astronomical Society, 2018
Published in: The Astrophysical Journal
Language: Not determined
DOI: 10.3847/1538-4357/aab040
ISSN: 0004-637X; 1538-4357
Keywords: Space and Planetary Science ; Astronomy and Astrophysics
Origination:
Footnote:
Description: <jats:title>Abstract</jats:title> <jats:p>Quasars may have played a key role in limiting the stellar mass of massive galaxies. Identifying those quasars in the process of removing star formation fuel from their hosts is an exciting ongoing challenge in extragalactic astronomy. In this paper, we present X-ray observations of 11 extremely red quasars (ERQs) with <jats:italic>L</jats:italic> <jats:sub>bol</jats:sub> ∼ 10<jats:sup>47</jats:sup> erg s<jats:sup>−1</jats:sup> at <jats:italic>z</jats:italic> = 1.5–3.2 with evidence for high-velocity (<jats:italic>v</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA $\geqslant $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaab040ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> 1000 km s<jats:sup>−1</jats:sup>) [O <jats:sc>iii</jats:sc>] <jats:italic>λ</jats:italic>5007 outflows. X-rays allow us to directly probe circumnuclear obscuration and to measure the instantaneous accretion luminosity. We detect 10 out of 11 ERQs available in targeted and archival data. Using a combination of X-ray spectral fitting and hardness ratios, we find that all of the ERQs show signs of absorption in the X-rays with inferred column densities of <jats:italic>N</jats:italic> <jats:sub>H</jats:sub> ≈ 10<jats:sup>23</jats:sup> cm<jats:sup>−2</jats:sup>, including four Compton-thick candidates (<jats:italic>N</jats:italic> <jats:sub>H</jats:sub> <jats:inline-formula> <jats:tex-math> <?CDATA $\geqslant $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaab040ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> 10<jats:sup>24</jats:sup> cm<jats:sup>−2</jats:sup>). We stack the X-ray emission of the seven weakly detected sources, measuring an average column density of <jats:italic>N</jats:italic> <jats:sub>H</jats:sub> ∼ 8 × 10<jats:sup>23</jats:sup> cm<jats:sup>−2</jats:sup>. The absorption-corrected (intrinsic) 2–10 keV X-ray luminosity of the stack is 2.7 × 10<jats:sup>45</jats:sup> erg s<jats:sup>−1</jats:sup>, consistent with X-ray luminosities of type 1 quasars of the same infrared luminosity. Thus, we find that ERQs are a highly obscured, borderline Compton-thick population, and based on optical and infrared data we suggest that these objects are partially hidden by their own equatorial outflows. However, unlike some quasars with known outflows, ERQs do not appear to be intrinsically underluminous in X-rays for their bolometric luminosity. Our observations indicate that low X-rays are not necessary to enable some types of radiatively driven winds.</jats:p>
Access State: Open Access

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