2024A&A...689A.247L

Context. IRASF11119+3257 is an ultra-luminous infrared galaxy with a post-merger morphology, hosting a type-1 quasar at z = 0.189. It shows a prominent ultra-fast outflow (UFO) absorption feature (v_out ∼ 0.25c) in its 2013 Suzaku spectrum. This is the first system in which the energy released by the UFO was compared to that of the known galaxy-scale molecular outflow to investigate the mechanism driving active galactic nuclei (AGN) feedback.
Aims. In 2021, we obtained the first XMM-Newton long look of the target, coordinated with a simultaneous NuSTAR observation, with the goal of constraining the broad band continuum and the nuclear wind physical properties and energetics with an unprecedented accuracy.
Methods. The new high-quality data allowed us to clearly detect at a confidence level P > 99.8% multiple absorption features associated with the known UFO at the 9.1 and 11.0 keV rest frames. Furthermore, an emission plus absorption feature at 1.1 - 1.3 keV reveals the presence of a blueshifted P-Cygni profile in the soft band.
Results. We associate the two hard band features with blends of FeXXV and FeXXVI Heα-Lyα and Heβ-Lyβ line pairs and infer a large column (N_H ∼ 10²⁴ cm^–2) of highly ionized (log ξ ∼ 5) gas outflowing at v_out = 0.27 ± 0.01c. The 1.3 keV absorption line can be associated with a blend of Fe and Ne transitions, produced by a lower column (N_H ∼ 3 × 10²¹ cm^–2) and ionization (log ξ ∼ 2.6) gas component outflowing at the same speed. Using a radiative-transfer disk wind model to fit the highly ionized UFO, we derive a mass outflow rate comparable with the mass accretion rate and the Eddington limit ($ {\dot{M}}_{\mathrm{out}}=4.25_{-0.73}^{+1.11}\, M_{\odot}/\mathrm{yr} $, ∼1.6 Ṁ_acc and ∼1.0 Ṁ_Edd), and kinetic energy ($ \dot E_{\mathrm{kin}}=1.21_{-0.20}^{+0.32}L_{\mathrm{bol}} $ and ∼0.7L_Edd) and momentum flux ($ {\dot P_{\mathrm{out}}}=6.37_{-1.09}^{+1.67} L_{\mathrm{bol}}/c $) among the highest reported in the literature. We measured an extremely low high-energy cutoff (E_cut ∼ 25 - 30 keV). This and several other cases in the literature suggest that a steep X-ray continuum may be related to the formation of powerful winds. We also analyzed the ionized [OIII] component of the large-scale outflow through optical spectroscopy and derived a large outflow velocity (v_out ∼ 3000 km/s) and energetics comparable with the large-scale molecular outflows. Finally, we observe a trend of decreasing outflow velocity from forbidden optical emission lines of decreasing ionization levels, interpreted as the outflow decelerating at large distances from the ionizing source.
Conclusions. The lack of a significant momentum boost between the nuclear UFO and the different phases of the large-scale outflow, observed in IRASF11119 and in a growing number of similar sources, can be explained by (i) a momentum-driven expansion, (ii) an inefficient coupling of the UFO with the host interstellar medium, or (iii) by repeated energy-driven expansion episodes with a low duty cycle, that average out on long timescales to produce the observed large-scale outflow.