巨大的暖/热星系日冕：II。等熵模型
Massive Warm/Hot Galaxy Coronae: II. Isentropic Model
摘要：
我们构造了一个新的$L^*$星系扩展环星系物质（CGM）解析唯象模型。我们的模型再现了银河系（MW）的OVII/OVIII吸收观测和COS-Halos和eCGM调查报告的OVI测量。暖/热气体在MW重力势中处于流体静力平衡，我们采用正压状态方程，导致温度变化作为半径的函数。包括绝热指数为$γ=4/3$的压力分量以近似磁场和宇宙射线的影响。我们引入了金属丰度梯度的激励内CGM的银河系的富集。然后，我们提出了我们的基准模型的日冕，调整到重现所观察到的OVI-OVIII柱密度，并与总质量$M_{\rm gas} \approx 5.5 \times 10^{10}~{\rm M_{\odot}}$内$r_{\rm cgm} \approx 280$千秒差距。CGM中的气体密度很低（$n_{\rm H} = 10^{-5} - 3 \times 10^{-4}~{\rm cm^{-3}}$），其碰撞电离态被元银河辐射场（MGRF）所改变。我们表明，OVI轴承温暖/热气体与典型的观察到的柱密度$N_{\rm OVI} \sim 3 \times 10^{14}~{\rm cm^{-2}}$在大（$\gtrsim 100$ kpc）的影响参数从中央星系，冷却动力学时间的比率，$t_{\rm cool}/t_{\rm dyn}$，有一个模型无关的上限$\lesssim 4$。在我们的模型中，大半径处的$t_{\rm cool}/t_{\rm dyn}$为$\sim 2-3$。我们提出的预测范围广泛的未来观测的温暖/热CGM，从UV/X射线吸收和发射光谱，色散测量（DM）和Sunyaev Zeldovich CMB测量。我们以机器可读的数据文件形式提供模型输出，便于比较和分析。
英文摘要：
We construct a new analytic phenomenological model for the extended circumgalactic material (CGM) of $L^*$ galaxies. Our model reproduces the OVII/OVIII absorption observations of the Milky Way (MW) and the OVI measurements reported by the COS-Halos and eCGM surveys. The warm/hot gas is in hydrostatic equilibrium in a MW gravitational potential, and we adopt a barotropic equation of state, resulting in a temperature variation as a function of radius. A pressure component with an adiabatic index of $γ=4/3$ is included to approximate the effects of a magnetic field and cosmic rays. We introduce a metallicity gradient motivated by the enrichment of the inner CGM by the Galaxy. We then present our fiducial model for the corona, tuned to reproduce the observed OVI-OVIII column densities, and with a total mass of $M_{\rm gas} \approx 5.5 \times 10^{10}~{\rm M_{\odot}}$ inside $r_{\rm cgm} \approx 280$ kpc. The gas densities in the CGM are low ($n_{\rm H} = 10^{-5} - 3 \times 10^{-4}~{\rm cm^{-3}}$) and its collisional ionization state is modified by the metagalactic radiation field (MGRF). We show that for OVI-bearing warm/hot gas with typical observed column densities $N_{\rm OVI} \sim 3 \times 10^{14}~{\rm cm^{-2}}$ at large ($\gtrsim 100$ kpc) impact parameters from the central galaxies, the ratio of the cooling to dynamical times, $t_{\rm cool}/t_{\rm dyn}$, has a model-independent upper limit of $\lesssim 4$. In our model, $t_{\rm cool}/t_{\rm dyn}$ at large radii is $\sim 2-3$. We present predictions for a wide range of future observations of the warm/hot CGM, from UV/X-ray absorption and emission spectroscopy, to dispersion measure (DM) and Sunyaev-Zeldovich CMB measurements. We provide the model outputs in machine-readable data files, for easy comparison and analysis.
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