We present new measurements of the spatial distribution and kinematics of neutral hydrogen in the circumgalactic and intergalactic medium surrounding star-forming galaxies at z ~ 2. Using the spectra of ~ 3000 galaxies with redshifts +/- 0.4 from the Keck Baryonic Structure Survey (KBSS), we assemble a sample of more than 200,000 distinct foreground-background pairs with projected angular separations of 3 - 500 arcsec and spectroscopic redshifts, with = 2.23 and = 2.57. The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess Ly$\alpha$ optical depth relative to the intergalactic mean as a function of projected galactocentric distance (20 100 kpc is dominated by infall with characteristic $v_{in}$ < $v_c$, where $v_c$ is the circular velocity of the host halo ($M_h$ ~ $10^{12} M_\odot$). Over the impact parameter range 80 < $D_{tran}$/pkpc < 200, the H I line-of-sight velocity range reaches a minimum, with a corresponding flattening in the rest-frame Ly$\alpha$ equivalent width. These observations can be naturally explained as the transition between outflow-dominated and accretion-dominated flows. Beyond $D_{tran}$ ~ 300 kpc, the line of sight kinematics are dominated by Hubble expansion.

中文翻译：

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凯克重子结构调查：使用前景/背景星系对追踪 z ∼ 2 处环星系中性氢的结构和运动学

我们提出了在 z ~ 2 处围绕恒星形成星系的环绕星系和星系际介质中中性氢的空间分布和运动学的新测量结果。 使用来自凯克重子结构调查 (KBSS) 的约 3000 个红移为 +/- 0.4 的星系的光谱)，我们组装了超过 200,000 个不同前景-背景对的样本，投影角间隔为 3 - 500 弧秒，光谱红移 = 2.23 和 = 2.57。视线和前景星系的集合用于构建相对于星系间平均值的平均超额 Ly$\alpha$ 光学深度的二维地图，作为投影星系中心距离的函数（20 100 kpc 由具有特征 $v_{ 的落入支配） in}$ < $v_c$，其中 $v_c$ 是宿主晕的圆周速度（$M_h$ ~ $10^{12} M_\odot$）。在冲击参数范围 80 < $D_{tran}$/pkpc < 200 内，HI 视线速度范围达到最小值，在静止帧 Ly$\alpha$ 等效宽度中相应变平。这些观察结果可以自然地解释为流出主导和吸积主导流动之间的过渡。超过 $D_{tran}$ ~ 300 kpc，视线运动学以哈勃膨胀为主。