Peering Through the Dust: NuSTAR Observations of Two FIRST-2MASS Red Quasars
Brandt, W. N.; Koss, Michael; Yaqoob, Tahir; Ricci, Claudio; Stern, Daniel; Urry, C. Megan; Hickox, Ryan C.; Boggs, Steve E.; Christensen, Finn E.; Craig, William W.; Treister, Ezequiel; Glikman, Eilat; Chen, Chien-Ting J.; Civano, Francesca; Harrison, Fiona; Lansbury, George B.; LaMassa, Stephanie M.; Ricarte, Angelo; Zhang, Will; Hailey, Chuck J.
United States, United Kingdom, Denmark, Switzerland, Chile
Abstract
Some reddened quasars appear to be transitional objects in the paradigm of merger-induced black hole growth/galaxy evolution, where a heavily obscured nucleus starts to be unveiled by powerful quasar winds evacuating the surrounding cocoon of dust and gas. Hard X-ray observations are able to peer through this gas and dust, revealing the properties of circumnuclear obscuration. Here, we present NuSTAR and XMM-Newton/Chandra observations of FIRST-2MASS-selected red quasars F2M 0830+3759 and F2M 1227+3214. We find that though F2M 0830+3759 is moderately obscured (NH,Z = (2.1 ± 0.2) × 1022 cm-2) and F2M 1227+3214 is mildly absorbed ({N}{{H},{{Z}}}={3.4}-0.7+0.8× {10}21 cm-2) along the line of sight, heavier global obscuration may be present in both sources, with {N}{{H},{{S}}}={3.7}-2.6+4.1× {10}23 cm-2 and <5.5 × 1023 cm-2 for F2M 0830+3759 and F2M 1227+3214, respectively. F2M 0830+3759 also has an excess of soft X-ray emission below 1 keV, which is well accommodated by a model where 7% of the intrinsic X-ray emission from the active galactic nucleus (AGN) is scattered into the line of sight. While F2M 1227+3214 has a dust-to-gas ratio (E(B - V)/NH) consistent with the Galactic value, the value of E(B - V)/NH for F2M 0830+3759 is lower than the Galactic standard, consistent with the paradigm that the dust resides on galactic scales while the X-ray reprocessing gas originates within the dust sublimation zone of the broad-line region. The X-ray and 6.1 μm luminosities of these red quasars are consistent with the empirical relations derived for high-luminosity, unobscured quasars, extending the parameter space of obscured AGNs previously observed by NuSTAR to higher luminosities.