Constraining cosmic ray transport with observations of the circumgalactic medium
Constraining cosmic ray transport with observations of the circumgalactic medium
复制标题
通过观察环绕星系介质来约束宇宙射线传输
DOI：
10.1093/mnras/stad671
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发表时间：
2023
影响因子：
4.8
通讯作者：
Hopkins, Philip F.
中科院分区：
文献类型：
--
作者：
Butsky, Iryna S.;Nakum, Shreya;Ponnada, Sam B.;Hummels, Cameron B.;Ji, Suoqing;Hopkins, Philip F.
最近的理论研究预测，低红移的星系周围的环星系介质（CGM）可能有大量的宇宙射线形式的非热压力支持。然而，这些预测对所采用的宇宙线传输的特定模型很敏感，这在理论上和观测上都是不受约束的。在这项工作中，我们提出了一个新的观测约束计算的径向平均，有效的宇宙线传输率的下限，。在广泛的假设（只要宇宙射线不失去显着的一部分，其能量在银盘，无论宇宙射线的压力是否是重要的或不CGM），我们证明了一个定义良好的关系和三个可观察到的星系属性：总氢柱密度，平均星星形成率，和气体的圆周速度。我们使用一套真实环境中的反馈2星系模拟与各种宇宙射线传输物理证明，我们的分析模型是一个强大的下限的真实宇宙射线传输率。然后，我们应用我们的新模型来计算COS-Halos样本中的星系，并确认这已经揭示了有效传输率的强有力证据，该传输率迅速上升远离星际介质的值（对应于各向异性流速度）在弥漫CGM中，在影响参数大于50-100 kpc。我们将讨论如何在未来的观测可以提供新的定性约束，我们在CGM和星系际介质中的宇宙射线的理解。
Recent theoretical studies predict that the circumgalactic medium (CGM) around low-redshift, ∼L*galaxies could have substantial non-thermal pressure support in the form of cosmic rays. However, these predictions are sensitive to the specific model of cosmic ray transport employed, which is theoretically and observationally underconstrained. In this work, we propose a novel observational constraint for calculating the lower limit of the radially averaged, effective cosmic ray transport rate,. Under a wide range of assumptions (so long as cosmic rays do not lose a significant fraction of their energy in the galactic disc, regardless of whether the cosmic ray pressure is important or not in the CGM), we demonstrate a well-defined relationship betweenand three observable galaxy properties: the total hydrogen column density, the average star formation rate, and the gas circular velocity. We use a suite of Feedback in Realistic Environments 2 galaxy simulations with a variety of cosmic ray transport physics to demonstrate that our analytical model ofis a robust lower limit of the true cosmic ray transport rate. We then apply our new model to calculatefor galaxies in the COS-Halos sample, and confirm this already reveals strong evidence for an effective transport rate that rises rapidly away from the interstellar medium to values(corresponding to anisotropic streaming velocities of) in the diffuse CGM, at impact parameters larger than 50–100 kpc. We discuss how future observations can provide qualitatively new constraints in our understanding of cosmic rays in the CGM and intergalactic medium.