星系晕中弥漫的低电离气体对$z\simeq 0.03$ WHIM探测的质疑
Diffuse Low-Ionization Gas in the Galactic Halo Casts Doubts on $z\simeq 0.03$ WHIM Detections
摘要：
在这封信中，我们证明了两个声称的$z\simeq 0.03$ OVII K $α$吸收线从温热星系际介质（WHIM）沿着视线到耀变体H~2356-309（Buote等人，2009; Fang等人，2010年）和Mkn~501（Ren，Fang \& Buote，2014年）可能是银河系星际和环银河介质中弥漫的低电离金属介质产生的$z=0$ OII K $β$线的错误识别。我们对H 2356-309和Mkn 501的所有可用的高信噪比Chandra LETG和XMM-牛顿RGS光谱进行了详细的建模，并证明了沿这两条视线的$z\simeq 0.03$ WHIM吸收在统计上是不需要的。然而，我们的研究结果并不排除$z\simeq 0.03$ OVII K $α$吸收剂沿着H~2356-309的视线的小贡献。在我们的模型中，假定的$z = 0.031$ WHIM细丝的温度为T $= 3\times 10^5$ K，OVII柱密度为N $_{OV II} \le 4\times 10^{15}$ cm $^{-2}$，比以前报道的OVII柱密度小20倍，现在更符合宇宙流体动力学模拟的预期。
英文摘要：
In this Letter we demonstrate that the two claims of $z\simeq 0.03$ OVII K$α$ 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$β$ 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$α$ 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$_{OV II} \le 4\times 10^{15}$ cm$^{-2}$, twenty times smaller than the OVII column density previously reported, and now more consistent with the expectations from cosmological hydrodynamical simulations.
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