Abstract
Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN). In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionised and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ∼2.4 obtained with SINFONI in the H- and K-band. All the quasars show [OIII]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM < 500 km/s), which is spatially extended and associated with star formation in the host galaxy. On paper fast outflows are spatially anti-correlated with star-formation powered emission, i.e. star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50 - 100 M⊙/yr, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2) ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2) transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.
Highlights
Negative feedback from accreting black holes (BH) is considered a fundamental physical process in galaxy evolution: it is believed to inhibit the excessive growth of massive galaxies and to explain the steep stellar mass function at its high end, to explain the existence of the “red and dead” elliptical galaxies, and to provide a connection between the supermassive BH growth and host galaxy evolution (e.g., Hopkins et al, 2006)
The CO, [OIII]λ5007 and Hα maps clearly exhibits a cavity in the outflow region leading to the conclusion that a fraction of molecular gas has been removed from the galaxy by the outflow, but, at the same time, we have star-formation on-going in the rest of the galaxy
The comparison between the relation mass outflow rate and active galactic nuclei (AGN) luminosity obtained from molecular and ionized outflow suggests that outflow masses are mainly dominated by molecular gas
Summary
Negative feedback from accreting black holes (BH) is considered a fundamental physical process in galaxy evolution: it is believed to inhibit the excessive growth of massive galaxies and to explain the steep stellar mass function at its high end, to explain the existence of the “red and dead” elliptical galaxies, and to provide a connection between the supermassive BH growth and host galaxy evolution (e.g., Hopkins et al, 2006). Feedback from accreting BH, i.e., from an AGN, takes the form of a fast outflow accelerated by the AGN radiation pressure which pushes gas away from the host galaxy, suppressing both star formation activity and BH accretion (e.g., Fabian, 2012). Quenching in High-z QSOs confirmed the AGN feedback scenario by showing that the observed outflow rates are larger than the star formation rates and that they can expel the gas from the host galaxy on very short time scales (Cicone et al, 2014, and references therein). Recent ALMA CO observations have revealed massive molecular outflows in nearby Seyfert 2 galaxies with a outflow rate of an order of magnitude higher than the SFR (Combes et al, 2013; García-Burillo et al, 2014). I report the results obtained by Carniani et al (2015, 2016, 2017): the characterization of AGN-driven ionized outflows in a sample of quasars at z ∼ 2.4 and their interaction with the host galaxies
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