Diffuse Low-Ionization Gas in the Galactic Halo Casts Doubts on $z\simeq 0.03$ WHIM Detections

Abstract

In this Letter we demonstrate that the two claims of $z\simeq 0.03$ OVII K$\alpha$ absorption lines from Warm Hot Intergalactic Medium (WHIM) along the lines of sight to the blazars H~2356-309 (Buote et al., 2009; Fang et al., 2010) and Mkn~501 (Ren, Fang \& Buote, 2014) are likely misidentifications of the $z=0$ OII K$\beta$ line produced by a diffuse Low-Ionization Metal Medium in the Galaxy's Interstellar and Circum-Galactic mediums. We perform detailed modeling of all the available high signal-to-noise Chandra LETG and XMM-Newton RGS spectra of H 2356-309 and Mkn 501 and demonstrate that the $z\simeq 0.03$ WHIM absorption along these two sightlines is statistically not required. Our results, however, do not rule out a small contribution from the $z\simeq 0.03$ OVII K$\alpha$ absorber along the line of sight to H~2356-309. In our model the temperature of the putative $z=0.031$ WHIM filament is T$=3\times 10^5$ K and the OVII column density is N${}_{OVII}\le 4\times 10^{15}$ cm${}^{-2}$, twenty times smaller than the OVII column density previously reported, and now more consistent with the expectations from cosmological hydrodynamical simulations.

arXiv comment6 pages, 2 figures, accepted by MNRAS (Letter)

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• The Mass and Absorption Columns of Galactic Gaseous Halos
• The Physical Origins of the Identified and Still Missing Components of the Warm-Hot Intergalactic Medium: Insights from Deep Surveys in the Field of Blazar 1ES1553+113
• X-ray absorption towards high-redshift sources: probing the intergalactic medium with blazars
• To be or not to be: hot WHIM absorption in the blazar PKS 2155-304 sight line?
• What we learn from the X-ray grating spectra of Nova SMC 2016
• A hot gaseous galaxy halo candidate with Mg X absorption
• Carbon X-ray absorption in the local ISM: fingerprints in X-ray Novae spectra
• Detection capabilities of the Athena X-IFU for the warm-hot intergalactic medium using gamma-ray burst X-ray afterglows
• Searching for the warm-hot intergalactic medium using XMM-Newton high-resolution X-ray spectra
• Characterization of the warm--hot intergalactic medium near the Coma cluster through high--resolution spectroscopy of X Comae