AGN wind scaling relations and the co-evolution of black holes and galaxies

¹ INAF–Osservatorio Astronomico di Roma, via Frascati 33, 00078 Monteporzio Catone, Italy
e-mail: fabrizio.fiore@oa-roma.inaf.it
² INAF–Osservatorio Astronomico di Trieste, via G. Tiepolo 11, 34124 Trieste, Italy
³ Department of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ, UK
⁴ Dipartimento di Fisica e Astronomia, Alma Mater Studiorum – Universitá di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁵ INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁶ Dipartimento di Fisica e Astronomia, Universitá di Firenze, via G. Sansone 1, 50019 Sesto F.no, Firenze, Italy
⁷ Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Ave., Cambridge CB3 0HE, UK
⁸ INAF–Osservatorio Astronomico di Brera, via Brera 28, 20121 Milan, Italy
⁹ ETH, Institute for Astronomy, Department of Physics, Wolfgang-Pauli-Strasse 278093 Zurich, Switzerland
¹⁰ European Southern Observatory, Karl-Schwarzschild-str. 2, 85748 Garching bei München, Germany
¹¹ INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

Received: 4 August 2016
Accepted: 13 February 2017

Abstract

Context. Feedback from accreting supermassive black holes (SMBHs) is often identified as the main mechanism responsible for regulating star formation in active galactic nucleus (AGN) host galaxies. However, the relationships between AGN activity, radiation, winds, and star formation are complex and still far from being understood.

Aims. We study scaling relations between AGN properties, host galaxy properties, and AGN winds. We then evaluate the wind mean impact on the global star formation history, taking into account the short AGN duty cycle with respect to that of star formation.

Methods. We first collect AGN wind observations for 94 AGN with detected massive winds at sub-pc to kpc spatial scales. We then fold AGN wind scaling relations with AGN luminosity functions, to evaluate the average AGN wind mass-loading factor as a function of cosmic time.

Results. We find strong correlations between the AGN molecular and ionised wind mass outflow rates and the AGN bolometric luminosity. The power law scaling is steeper for ionised winds (slope 1.29 ± 0.38) than for molecular winds (0.76 ± 0.06), meaning that the two rates converge at high bolometric luminosities. The molecular gas depletion timescale and the molecular gas fraction of galaxies hosting powerful AGN driven winds are 3–10 times shorter and smaller than those of main sequence galaxies with similar star formation rate (SFR), stellar mass, and redshift. These findings suggest that, at high AGN bolometric luminosity, the reduced molecular gas fraction may be due to the destruction of molecules by the wind, leading to a larger fraction of gas in the atomic ionised phase. The AGN wind mass-loading factor η = Ṁ_OF/SFR is systematically higher than that of starburst driven winds.

Conclusions. Our analysis shows that AGN winds are, on average, powerful enough to clean galaxies from their molecular gas only in massive systems at z ≲ 2, i.e. a strong form of co-evolution between SMBHs and galaxies appears to break down for the least massive galaxies.