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Marvin Rose |
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"The Forbidden High
Ionization Lines of SDSS J113111.05+162739.5: The Aftermath of a
Black Hole Recoil in the Central Regions of a Galaxy?" |
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Originally detected as a "red quasar" based on 2MASS NIR data, the optical spectrum of Q1131+16 (z=0.1732) shows a spectrum that is unusually rich in Forbidden High Ionization Lines (FHILs) such as [NeV], [FeVI], [FeVII] & [FeX]. These FHILs are particularly strong when compared with the emission lines of low ionization species. The emission lines also have large equivalent widths, which allow the reddening and physical conditions to be determined with a high level of accuracy. Upon closer inspection of the spectra, clues to the origin of the unusually strong FHIL may be provided by the broad-line components to the Balmer lines. These features are found close to the narrow Hydrogen alpha and Hydrogen beta emission line components but are strongly redshifted. The velocity width of the broad emission is 1980±60 km/s (FWHM) and is shifted by 1920±60 km/s relative to the rest frame of the narrow-line region (NLR). The hierarchical assembly of galaxies predicts that there should be many black hole binaries which will eventually merge. After they merge it is believed that the resultant black hole recoils within its host galaxy. A plausible explanation for the redshifted broad Balmer features in Q1131+16 is that they are emitted by gas in the broad-line region, which has been dragged along with a recoiling black hole. In addition, the rich spectrum may be caused by the illumination of the circumnuclear torus and NLR by: the release of energy associated with the black hole merger; or the recoiling black hole is interacting with a clump of interstellar medium in the host galaxy as it moves outside the circumnuclear torus. |