Quasar feedback revealed by giant molecular outflows

Abstract

In the standard scenario for galaxy evolution young star-forming galaxies transform into red bulge-dominated spheroids, where star formation has been quenched. To explain this transformation, a strong negative feedback generated by accretion onto a central supermassive black hole is often invoked. The depletion of gas resulting from quasar-driven outflows should eventually stop star-formation across the host galaxy and lead the black hole to "suicide" by starvation. Direct observational evidence for a major quasar feedback onto the host galaxy is still missing, because outflows previously observed in quasars are generally associated with the ionized component of the gas, which only accounts for a minor fraction of the total gas content, and typically occurrs in the central regions. We used the IRAM PdB Interferometer to observe the CO(1−0) transition in Mrk 231, the closest quasar known. Thanks to the wide band we detected broad wings of the CO line, with velocities of up to 750 km s −1 and spatially resolved on the kpc scale. These broad CO wings trace a giant molecular outflow of about 700 M /year, far larger than the ongoing star-formation rate (∼200 M /year) observed in the host galaxy. This wind will totally expel the cold gas reservoir in Mrk 231 in about 10 7 yrs, therefore halting the starformation activity on the same timescale. The inferred kinetic energy in the molecular outflow is ∼1.2 × 10 44 erg/s, corresponding to a few percent of the AGN bolometric luminosity, which is very close to the fraction expected by models ascribing quasar feedback to highly supersonic shocks generated by radiatively accelerated nuclear winds. Instead, the contribution by the SNe associated with the starburst fall short by several orders of magnitude to account for the kinetic energy observed in the outflow. The direct observational evidence for quasar feedback reported here provides solid support to the scenarios ascribing the observed properties of local massive galaxies to quasar-induced large-scale winds.

Quantifying AGN-driven metal-enhanced outflows in chemodynamical simulations

“…We can also estimate the mass outflow rate to be ∼400 M yr −1 , which lies within the observed range 10 M yr −1 Ṁ out 10 3 M yr −1 (e.g. Feruglio et al 2010;Schönell et al 2014). The outflowing gas soon slows and entrains more gas, eventually stalling ∼100 kpc from the BH by t = 9.245 Gyr, when the rerun simulation ends.…”

“…The presence of outflows in luminous quasars and AGN has been evidenced in broad absorption lines (Lynds 1967). The nearest quasar Mrk 231 shows a multiphase outflow containing ionized, neutral (Rupke & Veilleux 2013;Teng et al 2014), and molecular gas (Feruglio et al 2010;Cicone et al 2012), which may be explained by a bipolar outflow and an accretion disc. Winds are also seen in Seyfert galaxies (e.g.…”

HERUS: A CO ATLAS FROM SPIRE SPECTROSCOPY OF LOCAL ULIRGs

“…The [N II] line is indicative of hot HII regions rather than the PDR and can be used to estimate the fraction of [C II] emission that comes from ionized gas, rather than from PDRs. In many cases, the [N II] line is partially resolved and relatively broad (see Figure 9) and a sinc-Gauss profile was used to model the line in many instances where FWHM of ∼300-400 km −1 were measured, Although broad, these widths are still significantly smaller than those in systems that unambiguously are shown to have massive outflows (e.g., Feruglio et al 2010;Cicone et al 2014) Water is the second most oxygenated molecule (following CO) in the warm interstellar medium of galaxies and has been detected by Herschel in observations of nearby ULIRGs (González-Alfonso et al 2010;Rangwala et al 2011;PereiraSantaella et al 2013). The HERUS ULIRGs are also found to be abundant in water lines, in particular the ortho-H 2 O lines, IRAS 23230-6926, IRAS 06206-6315), and where the water lines, although detected, are significantly weaker than the CO lines (IRAS 09022-3615, IRAS 10565+2448, NGC 6240).…”

X-shooter reveals powerful outflows in z ∼ 1.5 X-ray selected obscured quasi-stellar objects

“…Only very recently spatially resolved optical, far infrared and mm spectroscopic studies convincingly showed evidences for the existence of such processes in the form of the predicted energetic outflows in ULIRGs with Seyfert nuclei in the local Universe (e.g. Feruglio et al 2010;Fischer et al 2010;Rupke & Veilleux 2011;Villar-Martín et al 2011;Rodríguez-Zaurín et al 2013;Zhang et al 2011;Westmoquette et al 2012;Rupke & Veilleux 2013;Harrison et al 2014;McElroy et al 2014; see also Elvis 2000 for a discussion on the ubiquitous presence of winds in the AGN structure).…”