A first view of interstellar Fe-bearing dust grains with XRISM
Abstract
Understanding the reservoirs of iron (Fe) in our Galaxy is crucial for probing the mechanisms that drive dust grain growth in the interstellar medium (ISM). High-resolution X-ray absorption spectroscopy offers a powerful tool to investigate the chemistry of dust grains, particularly those containing Fe, through spectroscopic features near photoabsorption edges known as X-ray Absorption Fine Structures (XAFS). With the Resolve spectrometer aboard XRISM, we can now examine the Fe K-edge (7.1 keV) owing to its improved spectral resolution in this energy range. This enabled us to probe the dust grain chemistry in high Galactic column densities. In this work, we present a pilot study on dust grain chemistry through the Fe K-edge of the XRISM Performance Verification target GX 340+0. This source is a persistently bright low-mass X-ray binary with a hydrogen column density of 6.6x10^22 cm^-2 along the line of sight, providing sufficient optical depth at the Fe K-edge. By fitting combined dust and gas models, we find that Fe is depleted by 95% into dust along the line of sight towards the source. Moreover, we find evidence that 38% of the solid-phase Fe is in metallic iron, 47% in iron sulfides, and the remainder in silicates. The large contribution from metallic iron and iron sulfides differs from what is typically inferred from X-ray studies of diffuse ISM and may suggest that that these compounds become more significant reservoirs of Fe in higher column density Galactic sightlines.
Related
- Photodissociation of [Fex(C₂₄H₁₂)y]⁺ complexes in the PIRENEA setup: iron-polycyclic aromatic hydrocarbon clusters as candidates for very small interstellar grains.
- Catalytic formation of H2 on carbonaceous dust grains - implications for interstellar observations
- Interstellar disparity: N- vs O-bearing molecules: A multidisciplinary perspective across interstellar environments
- Dust Activity Evolution and Constraints on Icy Grains in the Interstellar Comet 3I/ATLAS
- The bar-driven central complex of NGC 6946: A panchromatic and spatially resolved view of its star formation history and interstellar medium
BibTeX
@misc{psaradaki2026first,
title = {{A first view of interstellar Fe-bearing dust grains with XRISM}},
author = {I. Psaradaki and L. Corrales and E. Costantini and M. Mehdipour and D. Rogantini and H. Takahasi and R. Ballhausen and P. Chakraborty and T. Nakagawa and R. K. Smith and S. Zeegers},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.14172},
eprint = {2610.14172},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.14172},
}
RIS
TY - UNPB
TI - A first view of interstellar Fe-bearing dust grains with XRISM
AU - I. Psaradaki
AU - L. Corrales
AU - E. Costantini
AU - M. Mehdipour
AU - D. Rogantini
AU - H. Takahasi
AU - R. Ballhausen
AU - P. Chakraborty
AU - T. Nakagawa
AU - R. K. Smith
AU - S. Zeegers
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2610.14172
UR - https://arxiv.org/abs/2610.14172
AB - Understanding the reservoirs of iron (Fe) in our Galaxy is crucial for probing the mechanisms that drive dust grain growth in the interstellar medium (ISM). High-resolution X-ray absorption spectroscopy offers a powerful tool to investigate the chemistry of dust grains, particularly those containing Fe, through spectroscopic features near photoabsorption edges known as X-ray Absorption Fine Structures (XAFS). With the Resolve spectrometer aboard XRISM, we can now examine the Fe K-edge (7.1 keV) owing to its improved spectral resolution in this energy range. This enabled us to probe the dust grain chemistry in high Galactic column densities. In this work, we present a pilot study on dust grain chemistry through the Fe K-edge of the XRISM Performance Verification target GX 340+0. This source is a persistently bright low-mass X-ray binary with a hydrogen column density of 6.6x10^22 cm^-2 along the line of sight, providing sufficient optical depth at the Fe K-edge. By fitting combined dust and gas models, we find that Fe is depleted by 95% into dust along the line of sight towards the source. Moreover, we find evidence that 38% of the solid-phase Fe is in metallic iron, 47% in iron sulfides, and the remainder in silicates. The large contribution from metallic iron and iron sulfides differs from what is typically inferred from X-ray studies of diffuse ISM and may suggest that that these compounds become more significant reservoirs of Fe in higher column density Galactic sightlines.
ER -