# Charge exchange in the ultraviolet: implication for interacting clouds in the core of NGC 1275

## TL;DR

This study explores the potential of UV charge exchange emission as a diagnostic tool for hot and cold matter interactions in astrophysical environments, specifically analyzing archival data of NGC 1275.

## Contribution

It introduces a new application of charge exchange modeling in the UV band and re-analyzes Hubble data to identify potential charge exchange lines in NGC 1275.

## Key findings

- Possible charge exchange lines detected at 1223.6 Å, 1242.4 Å, and 1244.0 Å.
- Lines are consistent with charge exchange between highly ionized and neutral matter.
- Detected velocity offset suggests outflowing gas related to the nucleus.

## Abstract

Charge exchange emission is known to provide a key diagnostic to the interface between hot and cold matter in many astrophysical environments. Most of the recent charge exchange studies focus on its emission in the X-ray band, but few on the UV part, although the latter can also provide a powerful probe of the charge exchange process. An atomic calculation, as well as an application to observed data, are presented to explore and describe the potential use of the UV data for the study of cosmic charge exchange. Using the newest charge exchange model in the SPEX code v3.03, we re-analyze an archival Hubble STIS data of the central region of NGC 1275. The NGC 1275 spectrum shows hints for three possible weak lines at about 1223.6~{\AA}, 1242.4~{\AA}, and 1244.0~{\AA}, each with a significance of about $2-3\sigma$. The putative features are best explained by charge exchange between highly ionized hydrogen, neon, and sulfur with neutral matter. The wavelengths of the charge exchange lines are found robustly with uncertainties $\leq 0.3$~{\AA}. The possible charge exchange emission shows a line-of-sight velocity offset of about $-3400$ km s$^{-1}$ with respect to the NGC 1275 nucleus, which resembles one of the Ly$\alpha$ absorbers reported in Baum et al. (2005). This indicates that the charge exchange lines might be emitted as the same position of the absorber, which could be ascribed to outflowing gas from the nucleus.