AGN feedback on molecular gas reservoirs in quasars at z ~ 2.4

¹ Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Ave., Cambridge CB3 0HE, UK
e-mail: sc888@mrao.cam.ac.uk
² Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
³ Dipartimento di Fisica e Astronomia, Università di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino ( Firenze), Italy
⁴ INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁵ INAF–Osservatorio Astronomico di Trieste, via G. Tiepolo 11, 34124 Trieste, Italy
⁶ Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁷ INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁸ Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, Mexico D.F. 04510, Mexico
⁹ INAF–Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
¹⁰ SNS – Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
¹¹ INAF–Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy
¹² Dipartimento di Matematica e Fisica, Università Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
¹³ European Southern Observatory, Karl-Schwarzschild-str. 2, 85748 Garching bei München, Germany
¹⁴ School of Physics and Astronomy, The Sackler Faculty of Exact Sciences, Tel-Aviv University, 69978 Tel-Aviv, Israel
¹⁵ Department of Physics, University of North Texas, Denton, TX 76203, USA
¹⁶ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
¹⁷ Excellence Cluster “Universe”, Boltzmannstr. 2, 85748 Garching bei München, Germany

Received: 21 February 2017
Accepted: 26 June 2017

Abstract

We present new ALMA observations aimed at mapping molecular gas reservoirs through the CO(3−2) transition in three quasars at z ≃ 2.4, LBQS 0109+0213, 2QZ J002830.4-281706, and [HB89] 0329-385. Previous [Oiii]λ5007 observations of these quasars showed evidence for ionised outflows quenching star formation in their host galaxies. Systemic CO(3−2) emission has been detected only in one quasar, LBQS 0109+0213, where the CO(3−2) emission is spatially anti-correlated with the ionised outflow, suggesting that most of the molecular gas may have been dispersed or heated in the region swept by the outflow. In all three sources, including the one detected in CO, our constraints on the molecular gas mass indicate a significantly reduced reservoir compared to main-sequence galaxies at the same redshift, supporting a negative feedback scenario. In the quasar 2QZ J002830.4-281706, we tentatively detect an emission line blob blue-shifted by v ~ − 2000 km s^-1 with respect to the galaxy systemic velocity and spatially offset by 0.2′′ (1.7 kpc) with respect to the ALMA continuum peak. Interestingly, such emission feature is coincident in both velocity and space with the ionised outflow as seen in [Oiii]λ5007. This tentative detection must be confirmed with deeper observations but, if real, it could represent the molecular counterpart of the ionised gas outflow driven by the Active Galactic Nucleus (AGN). Finally, in all ALMA maps we detect the presence of serendipitous line emitters within a projected distance ~160 kpc from the quasars. By identifying these features with the CO(3−2) transition, we find that the serendipitous line emitters would be located within | Δv | < 500 km s^-1 from the quasars, hence suggesting an overdensity of galaxies in two out of three quasars.