Advances in instrumentation have recently extended detailed measurements of gas kinematics to large samples of high-redshift galaxies. Relative to most nearby, thin disk 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 modeled, these effects can strongly bias dynamical mass measurements. We use high-resolution FIRE-2 cosmological zoom-in simulations to analyze 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_* > 10^11 M_sun at z=1). Selecting only snapshots where a disk is present, we calculate the rotational profile v_phi(r) of the cool (10^3.5 K < T < 10^4.5 K) gas and compare it to the circular velocity v_c=sqrt(GM/r). In the simulated galaxies, the gas rotation traces the circular velocity at intermediate radii, but the two quantities diverge significantly in the center and in the outer disk. Our simulations appear to over-predict observed rotational velocities in the centers 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%. 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.

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从模拟高红移星系中的气体运动学测量动力学质量

仪器的进步最近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，其中气体旋转准确地追踪引力势，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。如果没有正确建模，这些影响可能会严重偏置动态质量测量。我们使用高分辨率 FIRE-2 宇宙学放大模拟来分析物理效应，从气体运动学正确推断动力学质量必须考虑这些物理效应。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（M_* > 10^11 M_sun at z=1）的一系列星系特性。仅选择存在磁盘的快照，我们计算冷 (10^3.5 K < T < 10^4.5 K) 气体的旋转轮廓 v_phi(r) 并将其与圆周速度 v_c=sqrt(GM/r) 进行比较。在模拟的星系中，气体旋转在中间半径处追踪圆周速度，但是这两个量在中心和外盘中显着发散。我们的模拟似乎高估了在大质量星系中心观察到的旋转速度（可能是由于缺乏黑洞反馈），因此我们专注于更大的半径。在这些半径处的湍流压力梯度可以提供额外的径向支持和偏差动态质量测量，低达 40%。在内部和外部，由于例如条形、卫星和流入/流出，气体的运动可能明显是非圆形的。