Location and energetics of the ultra-fast outflow in PG 1448+273

¹ Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
e-mail: marco.laurenti@roma2.infn.it
² INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone, Italy
³ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁴ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
⁵ Space Science Data Center, SSDC, ASI, Via del Politecnico snc, 00133 Roma, Italy

Received: 12 September 2020
Accepted: 13 November 2020

Abstract

Context. Ultra-fast outflows (UFOs) are the most powerful disk-driven winds in active galactic nuclei (AGNs). Theoretical and observational evidence shows that UFOs play a key role in the AGN feedback mechanism. The mechanical power of the strongest UFOs may be enough to propagate the feedback to the host galaxies and ultimately shape the AGN-galaxy coevolution. It is therefore of paramount importance to fully characterize UFOs, their location, and energetics.

Aims. We study two XMM-Newton archival observations of the narrow-line Seyfert 1 galaxy PG 1448+273. We concentrate on the latest observation, whose spectrum is characterized by a strong absorption feature in the Fe K band. This feature represents the spectral imprint of a UFO, as confirmed by other independent analyses. We study this feature in detail with a novel modeling tool.

Methods. In order to constrain the physical properties of the UFO, we implemented the novel model called wind in the ionized nuclear environment (WINE) to fit the photoionized emission and absorption lines from a disk wind in X-ray spectra. WINE is a photoionization model that allows us to self-consistently calculate absorption and emission profiles. It also takes special relativistic effects into account.

Results. Our detection of the UFO in PG 1448+273 is very robust. The outflowing material is highly ionized, logξ = 5.53_−0.05^+0.04 erg s⁻¹ cm, has a high column density, N_H = 4.5_−1.1^+0.8 × 10²³ cm⁻², is ejected with a maximum velocity v₀ = 0.24_−0.06^+0.08 c (90% confidence level errors), and attains an average velocity v_avg = 0.152 c. WINE succeeds remarkably well to constrain a launching radius of r₀ = 77₋₁₉⁺³¹ r_S from the black hole. We also derive a lower limit on both the opening angle of the wind (θ >  72°) and the covering factor (C_f >  0.69). We find a mass outflow rate Ṁ_out = 0.65_−0.33^+0.44 M_⊙ yr⁻¹ = 2.0_−1.0^+1.3 Ṁ_acc and a high instantaneous outflow kinetic power Ė_out = 4.4_−3.6^+4.4 × 10⁴⁴ erg s⁻¹ = 24% L_bol = 18% L_Edd (1σ errors). We find that a major error contribution on the energetics is due to r₀, stressing the importance of an accurate determination through proper spectral modeling, as done with WINE. Finally, using 20 Swift (UVOT and XRT) observations together with the simultaneous Optical Monitor data from XMM-Newton, we also find that α_ox varied strongly, with a maximum excursion of Δα_ox = −0.7, after the UFO was detected, leading to a remarkable X-ray weakness. This may indicate a starving of the inner accretion disk due to the removal of matter through the wind, and it may have repercussions for the larger population of observed X-ray weak quasars.