An X-ray/SDSS sample

I. Multi-phase outflow incidence and dependence on AGN luminosity

¹ Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
e-mail: michele.perna4@unibo.it
² INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ INAF–Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy

Received: 29 December 2016
Accepted: 13 March 2017

Abstract

Aims. The connection between the growth of super-massive black holes (SMBHs) and the evolution of their host galaxies is nowadays well established, although the underlying mechanisms explaining their mutual relations are still debated. Multi-phase fast, massive outflows have been postulated to play a crucial role in this process. The aim of this work is to constrain the nature and the fraction of outflowing gas in active galactic nuclei (AGNs) as well as the nuclear conditions possibly at the origin of such phenomena.

Methods. We present a large spectroscopic sample of X-ray detected SDSS AGNs at z< 0.8 with a high signal-to-noise ratio in the [O III]λ5007 line to unveil the faint wings of the emission profile associated with AGN-driven outflows. We used X-ray and optical flux ratio diagnostics to select the sample. We derived physical and kinematic characterization by re-analysing optical (and X-ray) spectra.

Results. We derive the incidence of ionized (~40%) and atomic (<1%) outflows covering a wide range of AGN bolometric luminosity from 10⁴² to 10⁴⁶ erg/s. We also derive bolometric luminosities and X-ray bolometric corrections to test whether the presence of outflows is associated with an X-ray loudness, as suggested by our recent results obtained by studying high-z QSOs.

Conclusions. We study the relations between the outflow velocity inferred from [O III] kinematic analysis and different AGN power tracers, such as black hole mass (M_BH), [O III], and X-ray luminosity. We show a well-defined positive trend between outflow velocity and L_X, for the first time, over a range of 5 order of magnitudes. Overall, we find that in the QSO-luminosity regime and at M_BH> 10⁸M_⊙ the fraction of AGNs with outflows becomes >50%. Finally, we discuss our results about X-ray bolometric corrections and outflow incidence in cold and ionized phases in the context of an evolutionary sequence allowing two distinct stages for the feedback phase: first, an initial stage characterized by X-ray/optical obscured AGNs, in which the atomic gas is still present in the ISM and the outflow processes involve all the gas components and, second, a later stage associated with unobscured AGNs, in which the line of sight has been cleaned and the cold components have been heated or exhausted.