2009/07/21 by Xin Liu, Nadia L. Zakamska, Jenny E. Greene +3 · 3 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Doubly ionized oxygen #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma-ray bursts and supernovae #Luminosity #Physics #Population #Quasar #Redshift #Spectral line #Star formation #Stellar mass #Stellar population #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/702/2/1098
published as Astrophys.J. 702 (2009) 1098-1117 · 20 pages, 13 figures, 7 tables; accepted to ApJ
arxiv created 2009/07/21 · openalex publication_date 2009/08/18 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present deep Gemini GMOS optical spectroscopy of nine luminous quasars at redshifts z ∼ 0.5, drawn from the Sloan Digital Sky Survey type 2 quasar sample. Our targets were selected to have high intrinsic luminosities ( M V < −26 mag) as indicated by the [O iii ] λ5007 Å emission-line luminosity ( L [O iii ] ). Our sample has a median black hole mass of ∼10 8.8 M ☉ inferred assuming the local M BH –σ * relation and a median Eddington ratio of ∼0.7, using stellar velocity dispersions σ * measured from the G band. We estimate the contamination of the stellar continuum from scattered quasar light based on the strength of broad Hβ, and provide an empirical calibration of the contamination as a function of L [O iii ] ; the scattered-light fraction is ∼30% of L 5100 for objects with L [O iii ] = 10 9.5 L ☉ . Population synthesis indicates that young poststarburst populations (<0.1 Gyr) are prevalent in luminous type 2 quasars, in addition to a relatively old population (>1 Gyr) which dominates the stellar mass. Broad emission complexes around He ii λ4686 Å with luminosities up to 10 8.3 L ☉ are unambiguously detected in three out of the nine targets, indicative of Wolf–Rayet (WR) populations. Population synthesis shows that ∼5 Myr poststarburst populations contribute substantially to the luminosities (>50% of L 5100 ) of all three objects with WR detections. We find two objects with double cores and four with close companions. Our results may suggest that luminous type 2 quasars trace an early stage of galaxy interaction, perhaps responsible for both the quasar and the starburst activity.