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GALAXY FORMATION AND THE KINEMATICS OF DAMPED Lya SYSTEMS

机译：银河系的形成和阻尼Lya系统的运动学

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A model of damped Lya systems is presented based on randomly moving clouds in spherical halos. We use the Press-Schechter model for the abundance of halos and assume that each halo has a similar population of clouds, with total mass and spatial distribution constrained to fit observations of the column density distribution. We show that the kinematics of the multiple absorbing components revealed in absorption profiles of the low-ionization lines, presented by Prochaska & Wolf e, are consis- tent with our spherical halo model. The presence of multiple absorbing components with a large cover- ing factor, combined with the small impact parameters of the systems predicted in our analytical model and in numerical simulations, implies a high rate of energy dissipation in cloud collisions. We calculate the rate of energy dissipation in our model and show that it is far greater than the rate at which energy can be supplied by gravitational mergers of halos. This poses a possible problem for the model of merging protogalactic clumps of Haehnelt et al., based on numerical simulations. We also present new constraints on the amplitude of the power spectrum in hierarchical theories required to account for the observed velocity dispersion in the absorbers. We find that the linearly extrapolated rms fluctuation at redshift z = 4 on spheres of radius R = l00 km s-1 H- (z) [where H(z) is the Hubble constant at red- shift z] must be greater than 0.75. Although this limit is obtained on1y for our specific model of the absorbing components, it should not be highly model-dependent because the
机译：提出了一种基于球形光晕中随机移动的云的阻尼Lya系统模型。我们使用Press-Schechter模型计算大量的晕圈，并假设每个晕圈都具有相似的云量，总质量和空间分布受限制以适合观察列密度分布。我们证明了由Prochaska和Wolf e提出的低电离谱线的吸收曲线中揭示的多种吸收组分的运动学与我们的球形晕轮模型是一致的。具有大覆盖因子的多个吸收组件的存在，再加上我们的分析模型和数值模拟中预测的系统的较小冲击参数，意味着在云碰撞中能量耗散率很高。我们计算了模型中的能量耗散率，结果表明，它远大于光环的重力合并所能提供的能量耗散率。基于数值模拟，这对于合并Haehnelt等人的原银河系团块的模型提出了一个可能的问题。我们还提出了分层理论中对功率谱幅值的新约束，这些理论要求考虑吸收器中观察到的速度色散。我们发现，在半径R = 100 km s-1 H-（z）的球体上，红移z = 4时的线性外推rms波动[其中H（z）是红移z处的哈勃常数]必须大于0.75 。尽管此限制仅针对我们特定的吸收组件模型获得，但它不应高度依赖模型，因为

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