XRISM/Resolve Spectroscopy of the Central Engine in the Seyfert-1 AGN Mrk 279

TL;DR

This XRISM/Resolve study of Mrk 279 demonstrates that high-resolution Fe Kα spectroscopy can disentangle emission from the torus, BLR, and inner disk, revealing a multi-component central engine geometry in a Seyfert-1 AGN. By applying blurred mytorus and relativistic spei modeling alongside photoionized emission/absorption (pion), the authors constrain inner radii for Fe Kα components and detect a highly ionized Fe XXVI emission feature, with tentative hints of ultra-fast outflows at v ≈ 0.22c and 0.33c. The inferred wind properties imply large mass-outflow rates and substantial kinetic power under unity filling factors, but the UFO evidence remains modest and requires deeper observations to confirm; nonetheless, the results place Mrk 279 within a growing XRISM-driven picture of AGN central engines where the torus, BLR, and inner disk contribute distinct Fe K features. Overall, the study showcases XRISM’s capability to probe AGN feeding and feedback geometries and highlights the need for coordinated follow-up to test for fast winds and their role in galaxy evolution.

Abstract

High-resolution X-ray spectroscopy with XRISM gives an unprecedented view of the ``central engine'' in active galactic nuclei, providing unique insights into black hole accretion and feedback. We present an analysis of the first XRISM/Resolve spectrum of the Seyfert-1 galaxy Mrk 279, known for its complex line profiles and variability. The data reveal velocity components within the Fe K$_α$ emission line that can be associated with the inner face of the molecular torus ($r \geq 10^{4}~GM/c^{2})$, the broad line region (BLR; $r = 1650^{+5780}_{-1480}~GM/c^{2}$), and the inner accretion disk ($r = 81^{+280}_{-75}~GM/c^{2}$). We find evidence of low-velocity, highly ionized gas that contributes an H-like Fe XXVI emission line at 6.97 keV, confirming suggestions from prior low-resolution spectra. The data do not show slow winds in absorption, but two pairs of lines - consistent with He-like and H-like Fe shifted by $v\simeq 0.22c$ and $v\simeq 0.33c$ - improve the fit, and could represent an ultra-fast outflow (UFO). Their addition to the model only reduces the Akaike Information Criterion by 3.6 and 3.5, respectively, signaling modest support. Additional observations are needed to definitively test for the presence of fast X-ray winds in Mrk 279. We discuss these results in the context of the geometry of the central engine in AGN, emerging trends in XRISM studies of AGN, and the nature of the potential UFOs.

Figures (5)

• Figure 1: Lightcurves of the XRISM/Resolve observation of Mrk 279. The left panel shows the lightcurve of the full Resolve band, and the right panel shows the lightcurve of the filtered 6.3--6.5 keV band (6.1--6.3 keV in the observed frame). The red horizontal line in each panel indicates the mean rate in each band ($0.27\pm0.03\text{ counts s}^{-1}$ for the full band, $0.011\pm0.003\text{ counts s}^{-1}$ for 6.1--6.3 keV), and the horizontal dotted lines indicate the rms of the variations in each curve.
• Figure 2: Simple model of Mrk 279 with Gaussian broadened "mytorus" components. The full model is plotted in blue, while the continuum is shown in red. The individual "MYTorus" components are shown in orange, magenta, and purple, respectively. The data are plotted in the rest frame.
• Figure 3: The time-averaged XRISM/Resolve spectrum of Mrk 279. The data are plotted in the rest frame, and binned using the "optimal" algorithm for fitting, and by a further factor of 4.0. The model shown in red is the best-fit extended physical model, including three components for the neutral Fe K emission lines, photoionized emission contributing an H-like Fe XXVI line at 6.97 keV, and photoionized absorption from tentative fast wind components. The solid gray lines indicate the lab energies of the neutral Fe K$_{\alpha}$ and Fe K$_{\beta}$ lines. The dashed gray line indicates the lab energy for the Fe XXVI emission line. The blue and purple lines indicate He-like Fe XXV and H-like Fe XXVI line pairs from potential ultra-fast outflows at $v\simeq 0.22c$ and $v\simeq 0.33c$. Please see the text and Table 2.
• Figure 4: The zoomed-in spectrum and the best-fit extended physical model (red), including the breakdown of the components for Fe K emission lines and photionized emission/absorption lines. The data are plotted in the rest frame.
• Figure 5: A comparison of the inner radii measured for Fe K$_{\alpha}$ line components in a subset of XRISM spectra of local AGN. All of the radii are based on blurred "mytorus" modeling of Resolve spectra; please see the text for details. With several important caveats, this plot suggests that Resolve data are able to separate line emission from the inner disk, BLR, and torus, and capable of tracing trends with Eddington fraction.