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arXiv · 2607.13139

Fe K$α$ line from the Broad Line Region of PDS456 with XRISM/Resolve

Alfredo Luminari·Fabrizio Nicastro·Stefano Bianchi·Elias Kammoun
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Abstract

The high-luminosity, high-mass and likely super-Eddington quasar PDS 456 is known for its extremely dynamic environment. A wealth of observational features from the millimetric up to the X-ray band shows energetic outflows at all scales, from accretion disc up to galaxy scales. Broad Emission Lines in the optical and UV show significant widths and line-of-sight velocities. Moreover, NIR interferometry revealed a partially outflowing Broad Line Region. Thanks to the unprecedented energy resolution of the X-ray microcalorimeter Resolve onboard XRISM, we detect a neutral Fe K$α$ line, the main tracer of cold matter around AGNs. The line blueshift ($v_{\rm out}=2700$ km s$^{-1}$) and width ($σ\leq 700$ km s$^{-1}$) are on the lower bound of the range of values of the optical-UV emission lines, possibly suggesting a stratified medium. The derived column density, $N_{\rm H} \approx 10^{22}$ cm$^{-2}$, is significantly lower than what expected for Broad Line Regions, again in agreement with a composite emission. The very small Equivalent Width (9 eV) marks one of the smallest measurements in the literature and probes the high-luminosity end of the so-called Iwasawa-Taniguchi (or X-ray Baldwin) effect.

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Alfredo Luminari, Fabrizio Nicastro, Stefano Bianchi, Elias Kammoun. 2026-07-14. Fe K$α$ line from the Broad Line Region of PDS456 with XRISM/Resolve. https://arxiv.org/abs/2607.13139

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