Metal-Enriched Outflows in the Ultra-Luminous infrared Quasar Q1321+058

摘要

Quasar outflows may play important role in the evolution of its host galaxyand central black hole. In this paper, we present a detailed study of multipleoutflows in the obscured ultra-luminous infrared quasar Q1321+058. The outflowsreveal themselves in the complex optical and UV emission line spectrum, with abroad component blueshifted by 1650 km/s and a narrow component by 360 km/s,respectively.The higher velocity component shows ever strong N III] and strongSi III], in addition to strong [O III]5007 and [Ne III]3869 emission lines,suggesting an overabundance of N and Si relative to C. The abundance pattern isconsistent a fast chemical enriching process associated with a recentstarburst. The outflow extends to several tens to hundred parsecs from thequasar, and covers only a very small sky. We find that the outflow with lineemitting gas is energetically insufficient to remove the ISM of the hostgalaxy. The velocity range and the column density suggest that the outflowmight be part of the low ionization broad absorption line region as seen in asmall class of quasars. The optical and UV continuum is starlight-dominated andcan be modelled with a young-aged (1 Myr) plus an intermediate-aged (~0.5-1Gyr) stellar populations, suggesting a fast building of the stellar mass in thehost galaxy, consistent with the starburst-type metal abundances inferred fromthe high velocity outflow spectrum. The broad band spectral energy distributionshows that it is an obscured quasar with its bulk emission in the middleinfrared. The star formation rate, independently estimated from UV,far-infrared, and emission line luminosity, is much lower than that is requiredfor the co-evolution of the black hole and its host spheroid.