The Accretion History of AGN: A Newly Defined Population of Cold Quasars

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Citation of Original Publication

Kirkpatrick, Allison; Urry, C. Megan; Brewster, Jason; Cooke, Kevin C.; Estrada, Michael; Glikman, Eilat; Hamblin, Kurt; Ananna, Tonima Tasnim; Carlile, Casey; Coleman, Brandon; Johnson, Jordan; Kartaltepe, Jeyhan S.; LaMassa, Stephanie M.; Marchesi, Stefano; Powell, Meredith; Sanders, Dave; Treister, Ezequiel; Turner, Tracey Jane; The Accretion History of AGN: A Newly Defined Population of Cold Quasars; Astrophysics of Galaxies (2019);


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Quasars are the most luminous of active galactic nuclei (AGN), and are perhaps responsible for quenching star formation in their hosts. The Stripe 82X catalog covers 31.3 deg² of the Stripe 82 field, of which the 15.6 deg² covered with XMM-Newton is also covered by Herschel/SPIRE. We have 2500 X-ray detected sources with multi-wavelength counterparts, and 30% of these are unobscured quasars, with LX > 10⁴⁴ erg/s and MB < −23. We define a new population of quasars which are unobscured, have X-ray luminosities in excess of 10⁴⁴ erg/s, have broad emission lines, and yet are also bright in the far-infrared, with a 250 µm flux density of S₂₅₀ > 30 mJy. We refer to these Herscheldetected, unobscured quasars as “Cold Quasars”. A mere 4% (23) of the X-ray- and optically-selected unobscured quasars in Stripe 82X are detected at 250 µm. These Cold Quasars lie at z ∼ 1 − 3, have Mdust ∼ 10⁸ −10⁹ M , have LIR > 10¹² L , and have star formation rates of 200−2000 M /yr. Cold Quasars are bluer in the mid-IR than the full quasar population, and 75% of our Cold Quasars have WISE W3 < 11.5 [Vega], while only 19% of the full quasar sample meets this criteria. Crucially, Cold Quasars have 4−7× as much star formation as the unobscured quasar population at similar redshifts. This phase is likely short-lived, as the central engine and immense star formation consume the gas reservoir. Cold Quasars are type-1 blue quasars that reside in starburst galaxies.