Magnetic fields on FIRE: Comparing B-fields in the multiphase ISM and CGM of simulated L* galaxies to observations
Magnetic fields on FIRE: Comparing B-fields in the multiphase ISM and CGM of simulated L* galaxies to observations
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FIRE 上的磁场：将模拟 L* 星系的多相 ISM 和 CGM 中的 B 场与观测结果进行比较
DOI：
10.1093/mnras/stac2448
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发表时间：
2022
影响因子：
4.8
通讯作者：
Hayward, Christopher C.
中科院分区：
文献类型：
--
作者：
Ponnada, Sam B.;Panopoulou, Georgia V.;Butsky, Iryna S.;Hopkins, Philip F.;Loebman, Sarah R.;Hummels, Cameron;Ji, Suoqing;Wetzel, Andrew;Faucher-Giguère, Claude-André;Hayward, Christopher C.
磁场(B)和宇宙射线(CRS)的物理学最近被纳入星系形成的模拟中。然而，这些成分如何影响星系演化仍存在重大不确定性。为了了解它们共同的观测示踪，我们分析了FIRE-2项目中一组高分辨率、磁流体动力学的类银河系宇宙学模拟中的磁场。我们比较了有或没有CRS的模拟磁场示踪剂的模拟观测与塞曼分裂和旋转/色散测量的观测。我们发现，在中性和电离星际介质(ISM)中，模拟和观测之间都有合理的一致性。我们发现，与只有磁场的星系相比，有CRS的模拟星系平均显示出更弱的ISM|B|场。这是CRS在弥漫的、低密度的内环星系介质(CGM)中的效应的一种表现。我们发现，对于银河系星系的典型ISM密度，磁能密度和宇宙线能量密度之间的均分在大尺度(>；1 kpc)上可能是有效的，但在它们的晕中是无效的。在ISM中，我们模拟的星系中的磁场遵循与气体密度成幂函数的比例关系。与观测得出的模型相反，标度向下延伸到中性氢数密度<；300xcm−3，但与观测测量一致。最后，我们为模拟星系的投影生成了合成旋转测量(RM)轮廓，并与CGM中的观测约束进行了比较。虽然与上限一致，但需要改进的数据来检测10-200kpc的预测CGM RMS，并更好地约束理论预测。
The physics of magnetic fields (B) and cosmic rays (CRs) have recently been included in simulations of galaxy formation. However, significant uncertainties remain in how these components affect galaxy evolution. To understand their common observational tracers, we analyse the magnetic fields in a set of high-resolution, magnetohydrodynamic, cosmological simulations of Milky-Way-like galaxies from the FIRE-2 project. We compare mock observables of magnetic field tracers for simulations with and without CRs to observations of Zeeman splitting and rotation/dispersion measures. We find reasonable agreement between simulations and observations in both the neutral and the ionized interstellar medium (ISM). We find that the simulated galaxies with CRs show weaker ISM |B| fields on average compared to their magnetic-field-only counterparts. This is a manifestation of the effects of CRs in the diffuse, low density inner circumgalactic medium (CGM). We find that equipartition between magnetic and cosmic ray energy densities may be valid at large (> 1 kpc) scales for typical ISM densities of Milky-Way-like galaxies, but not in their haloes. Within the ISM, the magnetic fields in our simulated galaxies follow a power-law scaling with gas density. The scaling extends down to neutral hydrogen number densities < 300 cm−3, in contrast to observationally derived models, but consistent with the observational measurements. Finally, we generate synthetic rotation measure (RM) profiles for projections of the simulated galaxies and compare to observational constraints in the CGM. While consistent with upper limits, improved data are needed to detect the predicted CGM RMs at 10–200 kpc and better constrain theoretical predictions.