3 years ago

Molecular outflow and feedback in the obscured Quasar XID2028 revealed by ALMA.

E. Piconcelli, F. Fraternali, V. Casasola, V. Mainieri, A. Bongiorno, L. Busoni, G. Zamorani, F. Mannucci, M. Brusa, R. Gilli, C. Vignali, P. Santini, F. Duras, I. Georgiev, M. Bonaglia, E. Lusso, F. Vito, M. Perna, C. Feruglio, M. T. Sargent, G. Cresci, D. Lutz, N. Z. Scoville, S. Rabien, F. La Franca, F. Fiore, S. Carniani, G. Lanzuisi, E. Daddi, A. Marconi, A. Comastri, R. Paladino

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 represents a unique test case to study QSO 'feedback in action' at the peak epoch of AGN-galaxy coevolution. The QSO has been detected in the CO(5-4) transition and in the 1.3mm continuum, at ~30 and ~20 {\sigma} significance respectively, with both emissions confined in the central (<4 kpc) radius area. Our analysis suggests the presence of a fast rotating molecular disc (v~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, CO(2-1) and CO(3-2), we could derive a total gas mass of ~10$^{10}$ M$_\odot$, 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 40-75 Myr, reinforcing the result of atypical gas consumption conditions in XID2028, possibly due to feedback effects on the host galaxy. Finally, we also detect at ~5{\sigma} the presence of high velocity CO gas, which we interpret as a signature of galaxy-scale molecular outflow, spatially coincident with the ionised gas outflow. XID2028 represents therefore a unique case where the measurement of total outflowing mass (~500-800 M$_\odot$/yr) including the molecular and atomic components, in both the ionised and neutral phases, has been attempted for a high-z QSO.

Publisher URL: http://arxiv.org/abs/1712.04505

DOI: arXiv:1712.04505v2

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