Supermassive Black Hole Winds in X-rays -- SUBWAYS. VI. Interplay between the soft X-ray excess and ultra-fast outflows

Abstract

We present a broadband, multiwavelength study of the interplay between the soft X-ray excess (SE), ultra-fast outflows (UFOs), and warm absorbers (WAs) in 21 active galactic nuclei (AGN; 0.1 <= z <= 0.4) from the SUBWAYS project. We combine simultaneous or quasi-simultaneous UV, optical, and X-ray data from XMM-Newton (EPIC pn and OM), NuSTAR, and the Hubble Space Telescope. We model the SE using a two-coronae framework, in which a warm, optically thick corona (WC) produces the optical/UV and soft X-ray emission, while a hot, optically thin corona produces the hard X-ray continuum. We also test a hybrid model that adds relativistic reflection. The optical/UV coverage constrains the Comptonization seed photon temperature to 0.1-5.5 eV. The two-coronae model consistently describes the broadband emission, with WC electron temperatures kT_e ~ 0.1-0.9 keV and photon indices $\Gamma >2$, consistent with previous studies. However, 9/21 AGN require the hybrid model, suggesting that the SE has multiple origins whose relative contributions vary. This is especially evident in UFO hosts, where 4/7 observations favor the hybrid model. Compared with sources without UFOs, UFO hosts show lower WC temperatures, harder hot-corona spectra, and positive hardness ratios. These trends should be treated cautiously because of the small sample and their dependence on spectral parameters and instrumental response. We find no significant differences between AGN with and without WAs. Our correlation analysis finds links between the amplification factor and WC temperature, WC optical depth and hardness ratio, and WC slope and optical depth with UV luminosity. We also find a tentative anticorrelation between WC optical depth and UFO outflow velocity.

arXiv commentAccepted for publication in A&A, 24 pages, 9 figures, 7 tables, and online material can be found on Zenodo