Molecular outflow and feedback in an obscured Quasar at z∼1.5 revealed by ALMA

We imaged with ALMA and ARGOS/LUCI the molecular gas and the dust and stellar continuum in XID2028, an obscured QSO at z=1.593, where the presence of a massive outflow in the ionized gas component traced by the [O III]5007 emission has been resolved up to 10 kpc. This target does represent a unique test case to study QSO ‘feedback in action’ at the peak epoch of AGN- galaxy coevolution. The QSO has been detected both in the CO(5-4) transition and in the 1.3mm continuum, with emissions confined in the central ( < 4 kpc) radius area. Our analysis suggests the presence of a fast rotating molecular disc ( ∼ 400 km/s) on very compact scales, and well inside the galaxy extent seen in the rest-frame optical light ( ∼ 10 kpc, as inferred from the LUCI data). Adding available measurements in additional two CO transitions, we could derive a total gas mass of ∼ 10^10 Msun , thanks to a critical assessment of CO excitation and the comparison with Rayleigh-Jeans continuum estimate. This translates into a very low gas fraction ( < 5%) and depletion time scales of 35-80 Myr, reinforcing the result of atypical gas consumption conditions in XID2028, possibly due to feedback effects on the host galaxy. Finally, we observe an asymmetric profile of the CO(5-4) line, which suggests the presence of high velocity gas up to 700 km/s. An image of the blueshfited and redshifted CO wings provides the first detection of a spatially resolved, galaxy-scale molecular outflow at high-z, extended in opposite directions with the approaching component spatially coincident with the ionised gas outflow. The resolved, molecular outflow appear to be cospatial with the component observed int the ionised gas. XID2028 therefore represents the first example of molecular and ionised kpc scales outflows at high-z