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Register a new userEvidence for AGN-driven Outflows in Young Radio Quasars
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Minjin Kim
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We present near-infrared spectra of young radio quasars [P(1.4GHz) ~ 26-27 W/Hz] selected from the Wide-Field Infrared Survey Explorer. The detected objects have typical redshifts of z ~ 1.6-2.5 and bolometric luminosities ~ 10^47 erg/s. Based on the intensity ratios of narrow emission lines, we find that these objects are mainly powered by active galactic nuclei (AGNs), although star formation contribution cannot be completely ruled out. The host galaxies experience moderate levels of extinction, A(V) ~ 0-1.3 mag. The observed [O III] luminosities and rest-frame J-band magnitudes constrain the black hole masses to lie in the range ~ 10^8.9-10^9.7 solar mass. From the empirical correlation between black hole mass and host galaxy mass, we infer stellar masses of ~ 10^11.3-10^12.2 solar mass. The [O III] line is exceptionally broad, with full width at half maximum ~1300 to 2100 km/s, significantly larger than that of ordinary distant quasars. We argue that these large line widths can be explained by jet-induced outflows, as predicted by theoretical models of AGN feedback.
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We use SDSS spectra and optical to far-infrared photometry for a sample of 31 FeLoBAL QSOs to study the relationship between the AGN-driven outflows, and obscured star formation in their host galaxies. We find that FeLoBAL QSOs invariably have IR luminosities exceeding 10^12 Solar luminosities. The AGN supplies 75% of the total IR emission, on average, but with a range from 20% to 100%. We find a clear anticorrelation between the strength of the AGN-driven outflows and the contribution from star formation to the total IR luminosity, with a much higher chance of seeing a starburst contribution in excess of 25% in systems with weak outflows than in systems with strong outflows. Moreover, we find no evidence that this effect is driven by the IR luminosity of the AGN. We conclude that radiatively driven outflows from AGN act to curtail obscured star formation in the host galaxies of reddened QSOs to less than ~25% of the total IR luminosity. This is the most direct evidence yet obtained for `quasar mode AGN feedback.
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