论文标题
从OVIII观察到银河系中对宇宙射线的限制
Constraints on cosmic rays in the Milky Way circumgalactic medium from OVIII observations
论文作者
论文摘要
我们通过比较了OVIII离子的吸收系与CGM的分析模型的预测（PP）和等温模型的预测，从而限制了银河系介质（CGM）中的宇宙射线（CR）种群。对于静水平衡中的CGM，引入CR会抑制热压，并影响OVIII离子丰度。我们探讨了给出的CR压力与热压比的津贴（$ \ rm {p} _ {\ rm {crm {cr}}/\ rm {p} _ {\ rm {\ rm {th}} =η$），具有不同的边界条件，cgm质量的质量，散发性且差异化的差异和温度。我们发现，$η$的允许最大值为：PP模型中的$η\ Lessim10 $，IT模型中的$η\ lyssim6 $。我们还探索了$η$：上升（$η= ax $）的空间变化或半径下降（$η= a/x $）的空间变化，其中a是配置文件的归一化。特别是，与温度波动的比率升高的模型相比，CR与热压的比例下降更好（对于PP而言，较大的$σ_{\ rm ln t} $较大$σ_{\ rm ln t} $，并且较低）。下降的配置文件允许在IT和PP模型中分别允许$ a \ lyssim8 $和$ a \ lyssim10 $，从而在中央地区容纳$η\，（\ simeq 200）$的大价值，但在外部地区不可容纳。这些限制以及来自$γ$ ray和无线电背景的限制，对于建立包括CR人群在内的银河系CGM模型很有用。但是，较大的CR可以在冷阶段填充，这可能是规避这些约束的一种方法。
We constrain the cosmic ray (CR) population in the circumgalactic medium (CGM) of Milky Way by comparing the observations of absorption lines of OVIII ion with predictions from analytical models of CGM : precipitation (PP) and isothermal (IT) model. For a CGM in hydrostatic equilibrium, the introduction of CR suppresses thermal pressure, and affects the OVIII ion abundance. We explore the allowances given to the ratio of CR pressure to thermal pressure ($\rm{P}_{\rm{CR}}/\rm{P}_{\rm{th}}=η$), with varying boundary conditions, CGM mass content, photoionization by extragalactic ultraviolet background and temperature fluctuations. We find that the allowed maximum values of $η$ are : $η\lesssim10$ in the PP model and $η\lesssim6$ in the IT model. We also explore the spatial variation of $η$ : rising ($η=Ax$) or declining ($η=A/x$) with radius, where A is the normalization of the profiles. In particular, the models with declining ratio of CR to thermal pressure fare better than those with rising ratio with suitable temperature fluctuation (larger $σ_{\rm ln T}$ for PP and lower for IT). The declining profiles allow $A\lesssim8$ and $A\lesssim10$ in the case of IT and PP models, respectively, thereby accommodating a large value of $η\,(\simeq 200)$ in the central region, but not in the outer regions. These limits, combined with the limits derived from $γ$-ray and radio background, can be useful for building models of Milky Way CGM including CR population. However, the larger amount of CR can be packed in cold phase which may be one way to circumvent these constraints.
