METAL-ENRICHED OUTFLOWS IN THE ULTRALUMINOUS INFRARED QUASAR Q1321+058

Abstract

Quasar outflows may play important role in the evolution of its host galaxy and central black hole, and are most often studied in absorption lines. In this paper, we present a detailed study of multiple outflows in the obscured ultraluminous infrared quasar Q1321+058. The outflows reveal themselves in the complex optical and ultraviolet (UV) emission-line spectrum, with a broad component blueshifted by 1650 km s(-1) and a narrow component by 360 km s(-1), respectively. The higher velocity component shows ever strong N III] (N III]/C III] = 3.8 +/- 0.3 and N III]/C IV = 0.53) and strong Si III] (Si III]/C III] similar or equal to 1), in addition to strong [O III]lambda 5007 and [Ne III]lambda 3869 emission. A comparison of these line ratios with photoionization models suggests an overabundance of N and Si relative to C. The abundance pattern is consistent with a fast chemical enriching process associated with a recent starburst, triggered by a recent galaxy merger. The outflow extends to several tens to hundred parsecs from the quasar, and covers only a very small sky. We find that the outflow with line emitting gas is energetically insufficient to remove the interstellar medium of the host galaxy, but total kinetic energy may be much larger than suggested by the emission lines. The velocity range and the column density suggest that the outflow might be part of the low-ionization broad absorption line region as seen in a small class of quasars. The optical and UV continuum is starlight dominated and can be modeled with a young-aged (1 Myr) plus an intermediate-aged (similar to 0.5-1 Gyr) stellar populations, suggesting a fast building of the stellar mass in the host galaxy, consistent with the starburst-type metal abundances inferred from the high-velocity outflow spectrum. The broadband spectral energy distribution shows that it is an obscured quasar with its bulk emission in the middle infrared. The star formation rate, independently estimated from UV, far-infrared, and emission-line luminosity, is much lower than that is required for the co-evolution of the black hole and its host spheroid.