室女座星系团：射电与X射线中古老宇宙射线晕的案例研究
The Virgo Cluster as a Case Study for Ancient Cosmic Ray Halos in Radio and X-rays
浏览论文内容
中文总结 AI 辅助
本研究以室女座星系团为案例，结合X射线、射电和法拉第旋转观测，证明冷核内宇宙射线通过库仑加热和逆康普顿散射显著贡献压强与软X射线发射，解释了冷却速率异常和金属丰度抑制，并指出其逃逸宇宙射线谱较英仙座更软。
中文摘要 AI 辅助
室女座星系团是最近的冷核（CC）星系团，是X射线弱冷核类星系的典型代表。尽管X射线连续谱暗示存在巨大的冷却速率（$\gtrsim 10\\,{\rm M_{\odot}\\,yr^{-1}}$），但对较冷气体相、尘埃和恒星形成的测量显示，在M87核之外几乎没有冷却。同时，已知M87$^{\ast}$是宇宙射线（CR）轻子的丰富源，在射电和$\gamma$射线波段被观测到，而最近的射电观测表明，M87射电晕是低频的，其谱指数在离开注入区域和喷流后迅速变陡，这与一个老化的、低能量的宇宙射线族群一致。我们证明，将X射线和射电观测与更新的法拉第旋转对磁场的限制相结合，这意味着冷核半径（$\lesssim 40$kpc）内的宇宙射线必须通过库仑加热气体和逆康普顿（IC）散射微波背景光子至$\sim$keV的组合方式，对总压强和软X射线发射做出显著贡献。我们表明，这可以解释喷流/射电功率与X射线冷却光度之间的明显对应关系，以及为什么X射线推断的冷却速率看起来远大于其他观测结果。这也可以解释为什么中心$\lesssim 10\\,$kpc处X射线推断的金属丰度相对于紫外/光学推断的金属丰度（以波长依赖的方式）显得被抑制。与更极端的射电+X射线源（如英仙座星系团）相比，我们发现观测要求一个更软的'逃逸'宇宙射线谱（在距M87$^{\ast}$约$\gtrsim 1\\,$kpc之外逃逸或加速）。
英文摘要
Virgo is the nearest cool core (CC) galaxy cluster, and is archetypal of the class of X-ray weak CCs. Despite the X-ray continuum implying a large cooling rate ($\gtrsim 10\,{\rm M_{\odot}\,yr^{-1}}$), measurements of cooler gas phases, dust, and star formation show almost no cooling outside the M87 nucleus. It is also known that M87$^{\ast}$ is a prodigious source of cosmic ray (CR) leptons observed in radio and $γ$-rays, and recent radio observations have shown that the M87 radio halo is low-frequency and its spectral index steepens rapidly away from the injection region+jets, consistent with an aging, low-energy CR population. We demonstrate that coupling X-ray and radio to newer Faraday rotation limits on the magnetic field, this implies the CRs within the CC radius ($\lesssim 40$kpc) must contribute significantly to the total pressure and soft X-ray emission, through a combination of Coulomb heating the gas and inverse-Compton (IC) scattering microwave background photons to $\sim$keV. We show this can explain the apparent correspondence between jet/radio power and X-ray cooling luminosity, and why the X-ray inferred cooling rate appears much larger than otherwise observed. This would also explain why the central X-ray inferred metallicity at $\lesssim 10\,$kpc appears to be suppressed relative to the UV/optical inferred metallicity (in a wavelength-dependent manner). Compared to more extreme radio+X-ray sources like Perseus, we find the observations require a softer 'escaping' CR spectrum (escaping or accelerated outside $\gtrsim 1\,$kpc from M87$^{\ast}$).
发表机构
- California Institute of Technology（加州理工学院）
- Princeton University（普林斯顿大学）
机构由 AI 辅助整理，请以论文原文为准。
