Fast outflows and star formation quenching in quasar host galaxies

Abstract

Negative feedback from active galactic nuclei (AGN) is considered a key mechanism in shaping galaxy evolution. Fast, extended outflows are frequently detected in the AGN host galaxies at all redshifts and luminosities, both in ionised and molecular gas. However, these outflows are only potentially able to quench star formation, and we are still lacking decisive evidence of negative feedback in action. Here we present observations obtained with the Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) Hand K-band integral-field of two quasars at z ∼ 2.4 that are characterised by fast, extended outflows detected through the [Oiii]λ5007 line. The high signal-to-noise ratio of our observations allows us to identify faint narrow (FWHM < 500 km s −1 ) and spatially extended components in [Oiii]λ5007 and Hα emission associated with star formation in the host galaxy. This star formation powered emission is spatially anti-correlated with the fast outflows. The ionised outflows therefore appear to be able to suppress star formation in the region where the outflow is expanding. However, the detection of narrow spatially extended Hα emission indicates star formation rates of at least ∼50-90 M yr −1 , suggesting either that AGN feedback does not affect the whole galaxy or that many feedback episodes are required before star formation is completely quenched. On the other hand, the narrow Hα emission extending along the edges of the outflow cone may also lead also to a positive feedback interpretation. Our results highlight the possible double role of galaxy-wide outflows in host galaxy evolution.

Very Compact Millimeter Sizes for Composite Star-forming/AGN Submillimeter Galaxies

“…Instead, the extended sizes of the SMGs with the AGN-dominant class are puzzling. In line with the evolutionary scenarios of, e.g., Sanders et al (1988), Hopkins et al (2008), and Toft et al (2014) where SMGs evolve into QSOs, the extended sizes may be explained by positive AGN feedback by a growing supermassive black hole in the phase of star-formation quenching, as is suggested by simulations for luminous AGN/QSOs (e.g., Ishibashi & Fabian 2012;Zubovas et al 2013) and considered for some luminous QSOs (e.g., Carniani et al 2016). In fact, ASXDF1100.057.1, which is an SMG of the AGN-dominant class, has a QSO-like, near-IR morphology (Figure 4).…”

“…As a next step, it would be useful to test the hypothesis that SMGs are connected to the formation of the most massive galaxies, being triggered by major mergers, and then evolving into compact quiescent galaxies via quenching in a quasi-stellar object (QSO) phase (e.g., Sanders et al 1988;Hopkins et al 2008;Toft et al 2014). The compact submillimeter sizes of SMGs, including recent reports of the existence of subkiloparsec-scale starburst cores (Iono et al 2016;Ikarashi et al 2017;Oteo et al 2017), suggests that the intense starformation activity might be quenched by active galactic nuclei (AGN), as observed in some luminous QSOs (e.g., Maiolino et al 2012;Carniani et al 2016). However, previous X-ray (e.g., Alexander et al 2005;Wang et al 2013) and mid-infrared (IR; e.g., Ivison et al 2004;Coppin et al 2010;Serjeant et al 2010) studies indicate that some SMGs do harbor AGN.…”

The WISSH quasars project

“…Nesvadba et al 2006Nesvadba et al , 2008Harrison et al 2012Harrison et al , 2014Liu et al 2013;Carniani et al 2015;Perna et al 2015b) and infer their mass outflow rate and kinetic power, with measuredṀ andĖ kin up to ∼ 600 − 700 M ⊙ yr −1 and ∼ 0.01× L Bol , respectively. Furthermore, in some cases, the outflowing [OIII] emission has been found to be spatially anticorrelated with narrow Hα emission, which traces star formation in the host galaxy (Cano-Díaz et al 2012;Cresci et al 2015;Carniani et al 2016). These results are considered among the most compelling pieces of evidence of negative feedback from AGN reported so far.…”

X-ray spectroscopy of the z = 6.4 quasar SDSS J1148+5251

“…Ionized, atomic and molecular outflows are commonly observed towards local and high-z quasars (e.g. Feruglio et al 2010;Rupke & Veilleux 2011;Carniani et al 2015Carniani et al , 2016Feruglio et al 2015, see also Fabian (2012 for a review on this subject). In particular, observations of the CO(1-0) emission line in local ultra-luminous galaxies have found that a non-negligible fraction (from few% up to 30%) of the total H2 mass is located in outflows extended on ∼kpc scales (Cicone et al 2014).…”