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

Liyi Gu, Junjie Mao, Christopher P. O'Dea, Stefi A. Baum, Missagh Mehdipour, Jelle S. Kaastra

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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.
Original languageEnglish
Article numberA45
Number of pages8
JournalAstronomy and Astrophysics
Early online date26 Apr 2017
Publication statusPublished - 31 May 2017


  • atomic processes
  • galaxies
  • X-rays
  • ultraviolet

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