高红移成星星系：Angular Momentum和重子分数、湍流压力效应及Turbulence的起源
High-Redshift Star-Forming Galaxies: Angular Momentum and Baryon Fraction, Turbulent Pressure Effects and the Origin of Turbulence
摘要：
本文研究了一个高红移（z = 2）、具有高恒星形成率和湍流气体速度σ = 40 - 80 km/s的旋转星系样品的结构。用Mo，Mao，White（1998）（MMW）模型拟合观测到的盘旋转速度和半径需要异常大的盘自旋参数λ d> 0.1，盘-暗晕质量分数m d = 0.2，接近宇宙重子分数。这些星系分离成色散主导系统和旋转主导系统，色散主导系统的最大旋转速度vmax <200 km/s，盘半光半径rd = 1 - 3 kpc，而旋转主导系统的最大旋转速度vmax> 200 km/s，vmax/sigma> 3，rd = 4 - 8 kpc。对于分散占主导地位的样品，径向压力梯度部分补偿重力，降低旋转速度。在毫米波模型中考虑这种压力效应，色散支配星系的自旋参数在高盘质量分数（m_d = 0.2）时为lf λ_d = 0.03 - 0.05，在高盘质量分数（m_d = 0.05）时为lf λ_d = 0.01 - 0.03。这些值与宇宙学的预期非常一致。然而，对于旋转为主的样品的压力效应是小的，更好的协议与理论上预期的磁盘自旋参数可以实现，如果在可见磁盘制度（2 - 3 * rd）的暗晕质量贡献小于MMW模型预测。我们认为，这些星系仍然可以嵌入在标准的冷暗物质晕，如果晕没有收缩的磁盘形成的反应。结果表明，所观察到的高湍流气体运动的星系是一致的Toomre不稳定性参数Q = 1，这是等于临界值，预计引力盘不稳定性是湍流的主要驱动程序。湍流的主要能量来源是圆盘中气体的势能。
英文摘要：
The structure of a sample of high-redshift (z=2), rotating galaxies with high star formation rates and turbulent gas velocities of sigma=40-80 km/s is investigated. Fitting the observed disk rotational velocities and radii with a Mo, Mao, White (1998) (MMW) model requires unusually large disk spin parameters lambda_d>0.1 and disk-to-dark halo mass fraction m_d=0.2, close to the cosmic baryon fraction. The galaxies segregate into dispersion-dominated systems with 1<vmax/sigma<3, maximum rotational velocities vmax<200 km/s and disk half-light radii rd=1-3 kpc and rotation-dominated systems with vmax>200 km/s, vmax/sigma>3 and rd=4-8 kpc. For the dispersion-dominated sample, radial pressure gradients partly compensate the gravitational force, reducing the rotational velocities. Including this pressure effect in the MMW model, dispersion-dominated galaxies can be fitted well with spin parameters lf lambda_d=0.03-0.05 for high disk mass fractions of m_d=0.2 and with lambda_d=0.01-0.03 for m_d=0.05. These values are in good agreement with cosmological expectations. For the rotation-dominated sample however pressure effects are small and better agreement with theoretically expected disk spin parameters can only be achieved if the dark halo mass contribution in the visible disk regime (2-3*rd) is smaller than predicted by the MMW model. We argue that these galaxies can still be embedded in standard cold dark matter halos if the halos did not contract adiabatically in response to disk formation. It is shown that the observed high turbulent gas motions of the galaxies are consistent with a Toomre instability parameter Q=1 which is equal to the critical value, expected for gravitational disk instability to be the major driver of turbulence. The dominant energy source of turbulence is then the potential energy of the gas in the disk.
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