High-resolution X-ray spectroscopy in the XRISM era

Overview

For decades, the iron features that carry so much information about the gas around a black hole were smeared together by the limited resolution of X-ray detectors. The microcalorimeter on XRISM changed that. It resolves the iron K complex finely enough to separate its components by their motion, letting us pick apart the inner accretion disk, the broad-line region, and the more distant obscuring gas that used to blend into a single blur.

Approach

I lead several XRISM Guest Observer programs that use this new resolving power to study the structure of the gas around accreting supermassive black holes, supported by simultaneous XMM-Newton, NuSTAR, and optical observations. The programs target the X-ray broad-line region, the fine structure of the iron line in individual sources, and the separation of components in dual-AGN candidates.

Key results

• In NGC 7213, XRISM resolves the iron emission into a narrow core, a broader disk-like component, and highly ionized lines whose locations bridge the inner disk and the optical broad-line region, revealing a radially stratified structure that was invisible before.
• Applied across nearby AGN, these high-resolution spectra are reshaping how we picture the multiple phases of gas surrounding a growing black hole.