SUPER

V. ALMA continuum observations of z ∼ 2 AGN and the elusive evidence of outflows influencing star formation

¹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
e-mail: isabellalamperti@gmail.com
² Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
³ Centro de Astrobiología (CAB, CSIC-INTA), Departamento de Astrofísica, Ctra. de Ajalvir Km. 4, 28850 Torrejón de Ardoz, Madrid, Spain
⁴ School of Mathematics, Statistics and Physics, Herschel Building, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
e-mail: christopher.harrison@newcastle.ac.uk
⁵ European Southern Observatory, Alonso de Cordova 3107, Casilla 19, Santiago 19001, Chile
⁶ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁷ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁸ Chalmers University of Technology, Department of Earth and Space Sciences, Onsala Space Observatory, 43992 Onsala, Sweden
⁹ Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
¹⁰ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
¹¹ Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
¹² INAF – Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
¹³ Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
¹⁴ Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
¹⁵ Escuela de Física – Universidad Industrial de Santander, 680002 Bucaramanga, Colombia
¹⁶ School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel
¹⁷ INAF – Osservatorio Astronomico di Roma, Via di Frascati 33, 00078 Monte Porzio Catone, Italy
¹⁸ Graduate School of Science and Engineering, Saitama Univ. 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan
¹⁹ INAF IASF-Milano, Via Alfonso Corti 12, 20133 Milano, Italy
²⁰ Dipartimento di Fisica e Astronomia, Alma Mater Studiorum, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
²¹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy

Received: 21 May 2021
Accepted: 30 August 2021

Abstract

We study the impact of active galactic nuclei (AGN) ionised outflows on star formation in high-redshift AGN host galaxies, by combining near-infrared integral field spectroscopic (IFS) observations, mapping the Hα emission and [O III]λ5007 outflows, with matched-resolution observations of the rest-frame far-infrared (FIR) emission. We present high-resolution ALMA Band 7 observations of eight X-ray selected AGN (L_{2 − 10 keV} = 10^43.8 − 10^45.2 erg s⁻¹) at z ∼ 2 from the SUPER (SINFONI Survey for Unveiling the Physics and Effect of Radiative feedback) sample, targeting the observed-frame 870 μm (rest-frame ∼260 μm) continuum at ∼2 kpc (0.2″) spatial resolution. The targets were selected among the SUPER AGN with an [O III] detection in the IFS maps and with a detection in the FIR photometry. We detected six out of eight targets with signal-to-noise ratio S/N ≳ 10 in the ALMA maps, from which we measured continuum flux densities in the range 0.27 − 2.58 mJy and FIR half-light radii (R_e) in the range 0.8 − 2.1 kpc. The other two targets were detected with S/N of 3.6 and 5.9, which are insufficient for spatially resolved analysis. The FIR R_e of our sample are comparable to other AGN and star-forming galaxies at a similar redshift from the literature. However, combining our sample with the literature samples, we find that the mean FIR size in X-ray AGN (R_e = 1.16 ± 0.11 kpc) is slightly smaller than in non-AGN (R_e = 1.69 ± 0.13 kpc). From spectral energy distribution fitting, we find that the main contribution to the 260 μm flux density is dust heated by star formation, with ≤4% contribution from AGN-heated dust and ≤1% from synchrotron emission. The majority of our sample show different morphologies for the FIR (mostly due to reprocessed stellar emission) and the ionised gas emission (Hα and [O III], mostly due to AGN emission). This could be due to the different locations of dust and ionised gas, the different sources of the emission (stars and AGN), or the effect of dust obscuration. We are unable to identify any residual Hα emission, above that dominated by AGN, that could be attributed to star formation. Under the assumption that the FIR emission is a reliable tracer of obscured star formation, we find that the obscured star formation activity in these AGN host galaxies is not clearly affected by the ionised outflows. However, we cannot rule out that star formation suppression is happening on smaller spatial scales than the ones we probe with our observations (< 2 kpc) or on different timescales.