# X-ray extinction from interstellar dust: Prospects of observing carbon, sulfur and other trace elements

## TL;DR

This study explores the potential of future X-ray instruments to observe and analyze the presence and chemistry of trace elements like carbon, sulfur, aluminum, calcium, titanium, and nickel in interstellar dust through extinction features.

## Contribution

It assesses the detectability of interstellar dust components and their chemical states using simulated data from upcoming X-ray missions, incorporating laboratory measurements and dust models.

## Key findings

- Carbon and sulfur chemistry can be characterized with future X-ray observations.
- Large grain extinction signatures can be detected and modeled.
- Titanium and nickel will be challenging to study due to low abundance.

## Abstract

We present a study on the prospects of observing carbon, sulfur, and other lower abundance elements (namely Al, Ca, Ti and Ni) present in the interstellar medium using future X-ray instruments. We focus in particular on the detection and characterization of interstellar dust along the lines of sight. We compare the simulated data with different sets of dust aggregates, either obtained from past literature or measured by us using the SOLEIL-LUCIA synchrotron beamline. Extinction by interstellar grains induces modulations of a given photolelectric edge, which can be in principle traced back to the chemistry of the absorbing grains. We simulated data of instruments with characteristics of resolution and sensitivity of the current Athena, XRISM and Arcus concepts. In the relatively near future, the depletion and abundances of the elements under study will be determined with confidence. In the case of carbon and sulfur, the characterization of the chemistry of the absorbing dust will be also determined, depending on the dominant compound. For aluminum and calcium, despite the large depletion in the interstellar medium and the prominent dust absorption, in many cases the edge feature may not be changing significantly with the change of chemistry in the Al$^-$ or Ca$^-$ bearing compounds. The exinction signature of large grains may be detected and modeled, allowing a test on different grain size distributions for these elements. The low cosmic abundance of Ti and Ni will not allow us a detailed study of the edge features.