• DOI:10.3847/1538-4357/abd03f
• Corpus ID: 222140633

Probing the Hot Circumgalactic Medium with Broad O vi and X-Rays

@article{Mathur2020ProbingTH,
  title={Probing the Hot Circumgalactic Medium with Broad O vi and X-Rays},
  author={Smita Mathur and Anjali Gupta and Sanskriti Das and Yair Krongold and Fabrizio Nicastro},
  journal={The Astrophysical Journal},
  year={2020},
  volume={908}
}

• S. Mathur, Anjali Gupta, +2 authors F. Nicastro
• Published 5 October 2020
• Physics
• The Astrophysical Journal

Most of the baryonic mass in the circumgalactic medium (CGM) of a spiral galaxy is believed to be warm-hot, with temperature around 106 K. The narrow O vi absorption lines probe a somewhat cooler component at , but broad O vi absorbers have the potential to probe the hotter CGM. Here we present 376 ks Chandra LETG observations of a carefully selected galaxy in which the presence of broad O vi together with the non-detection of Lyα was indicative of hot gas. The strongest line expected to be present at ≈106 K is O vii λ21.602. There is a hint of an absorption line at the redshifted wavelength, but the line is not detected with better than 2σ significance. A physical model, taking into account strengths of several other lines, provides better constraints. Our best-fit absorber model has and . These parameters are consistent with the hot plasma model based on UV observations; other O vi models of cooler gas phases are ruled out at better than 99% confidence. Thus we have suggestive, but not conclusive evidence for the broad O vi absorber probing the hot gas from the shallow observations of this pilot program. About 800 ks of XMM-Newton observations will detect the expected absorption lines of O vii and O viii unequivocally. Future missions like XRISM, Arcus, and Athena will revolutionize the CGM science.