Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies
Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies
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DOI：
10.1093/mnras/staa2229
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发表时间：
2019-08
影响因子：
4.8
通讯作者：
S. Wellons;C. Faucher-Giguère;D. Anglés-Alcázar;C. Hayward;R. Feldmann;P. Hopkins;D. Keres̆
中科院分区：
文献类型：
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作者：
S. Wellons;C. Faucher-Giguère;D. Anglés-Alcázar;C. Hayward;R. Feldmann;P. Hopkins;D. Keres̆
最近，仪器的进步将气体运动学的详细测量扩展到高红移星系的大样本。相对于大多数附近的薄盘星系，在这些星系中，气体旋转精确地追踪了引力势，$z$ > 1星系的星际介质（ISM）通常更具动态性，并表现出更高的湍流。如果建模不当，这些效应会严重影响动态质量测量。我们使用高分辨率的FIRE-2宇宙学放大模拟来分析从气体运动学中正确推断动力质量必须考虑的物理效应。我们的分析涵盖了从低红移银河系质量星系到大质量高红移星系的一系列星系特性（M -百科> 1011 M⊙at $z$ = 1）。只选择存在圆盘的快照，我们计算冷气体（$10^{3.5}\,\lt {\it T}\lt 10^{4.5}~\rm {K}$）的旋转轮廓$\bar{v}_\phi (r)$，并将其与圆速度$v_{\rm c}=\sqrt{GM_{\rm enc}/r}$进行比较。在模拟的星系中，气体旋转在中间半径处遵循圆周速度，但这两个量在中心和外盘明显不同。我们的模拟似乎过度预测了在大质量星系中心观测到的旋转速度（可能是因为缺乏黑洞反馈），所以我们把重点放在更大的半径上。在这些半径处，湍流压力的梯度可以提供额外的径向支持，并使动态质量测量偏差降低40％。在内部和外部，气体的运动可能明显是非圆形的，例如，由于棒，卫星和流入/流出。我们讨论了高红移星系ISM中常用的压力梯度（或“不对称漂移”）分析模型的准确性。
Advances in instrumentation have recently extended detailed measurements of gas kinematics to large samples of high-redshift galaxies. Relative to most nearby, thin disc galaxies, in which gas rotation accurately traces the gravitational potential, the interstellar medium (ISM) of $z$ ≳ 1 galaxies is typically more dynamic and exhibits elevated turbulence. If not properly modelled, these effects can strongly bias dynamical mass measurements. We use high-resolution FIRE-2 cosmological zoom-in simulations to analyse the physical effects that must be considered to correctly infer dynamical masses from gas kinematics. Our analysis covers a range of galaxy properties from low-redshift Milky-Way-mass galaxies to massive high-redshift galaxies (M⋆ > 1011 M⊙ at $z$ = 1). Selecting only snapshots where a disc is present, we calculate the rotational profile $\bar{v}_\phi (r)$ of the cool ($10^{3.5}\,\lt {\it T}\lt 10^{4.5}~\rm {K}$) gas and compare it to the circular velocity $v_{\rm c}=\sqrt{GM_{\rm enc}/r}$. In the simulated galaxies, the gas rotation traces the circular velocity at intermediate radii, but the two quantities diverge significantly in the centre and in the outer disc. Our simulations appear to over-predict observed rotational velocities in the centres of massive galaxies (likely from a lack of black hole feedback), so we focus on larger radii. Gradients in the turbulent pressure at these radii can provide additional radial support and bias dynamical mass measurements low by up to 40 per cent. In both the interior and exterior, the gas’ motion can be significantly non-circular due to e.g. bars, satellites, and inflows/outflows. We discuss the accuracy of commonly used analytic models for pressure gradients (or ‘asymmetric drift’) in the ISM of high-redshift galaxies.