We use detailed Lyalpha radiative transfer calculations to further test the claim of Rauch et al. (2008) that they have detected spatially extended faint Lyalpha emission from the elusive host population of Damped Lyalpha Absorption systems (DLAs) in their recent ultra-deep spectroscopic survey. We investigate the spatial and spectral distribution of Lyalpha emission due to star-formation at the centre of DLAs, and its dependence on the spatial and velocity structure of the gas. Our model simultaneously reproduces the observed properties of DLAs and the faint Lyalpha emitters, including the velocity width and column density distribution of DLAs and the large spatial extent of the emission of the faint emitters. Our modelling confirms previous suggestions that DLAs are predominately hosted by Dark Matter (DM) halos in the mass range 10^{9.5}-10^{12} M_sun, and are thus of significantly lower mass than those inferred for L_* Lyman Break Galaxies (LBGs). Our modelling suggests that DM halos hosting DLAs retain up to 20% of the cosmic baryon fraction in the form of neutral hydrogen, and that star formation at the centre of the halos is responsible for the faint Lyalpha emission. The scattering of a significant fraction of the Lyalpha emission to the observed radii, which can be as large as 50 kpc or more, requires the amplitude of the bulk motions of the gas at the centre of the halos to be moderate. The observed space density and size distribution of the emitters together with the incidence rate of DLAs suggests that the Lyalpha emission due to star formation has a duty cycle of ~ 25%.
Evolution of the Cool Gas in the Circumgalactic Medium (CGM) of Massive Halos -- A Keck Cosmic Web Imager (KCWI) Survey of Ly$α$ Emission around QSOs at $z\approx2$
最近发现$z \gtrsim 3$类星体周围的Ly $α$辐射几乎无处不在，我们利用Keck宇宙网成像仪（KCWI）--一种新的宽视场、蓝敏积分场摄谱仪（IFU）--的独特能力，在$z\approx2$对类星体环星系Ly $α$辐射进行了系统的研究。本文介绍了在$z=2.1-2.3$上对16个超亮I型类星体进行的KCWI观测，电离光度为$L_{\rm{ν_{\rm{LL}}}}=10^{31.1-32.3}$ erg s $^{-1}$ Hz $^{-1}$。我们发现，16个类星体中有14个与Ly $α$星云有关，其投影线性尺寸大于50物理千秒差距（pkpc）。其中，有四个星云具有巨大的Ly $α$辐射，其表面亮度为$SB_{\rm{Lyα}} >10^{-17}$ erg s $^{-1}$ cm $^{-2}$ arcsec $^{-2}$（$>100$ kpc尺度），超出了KCWI的视野范围。我们的KCWI观测显示，大多数$z\approx2$类星体星云的形态比$z\gtrsim3$的更不规则。反过来，我们测量到$z\approx2$处的圆平均表面亮度（SB）比$z\gtrsim 3$处的红移校正中值SB暗0.4 dex。类星体在$z\approx 2$的Ly $α$ SB廓线（SB $_{\rm{Lyα}}$）可用SB $_{\rm{Lyα},z\approx2.3}= 3…
Unveiling the mask on the ULIRG-to-QSO transition object [H89]1821+643 at z=0.3: a gas-poor/gas-rich galaxy merger and the implications for CO-based dynamical mass estimates
Metal-enriched, sub-kiloparsec gas clumps in the circumgalactic medium of a faint z = 2.5 galaxy
本文报道了在一个明亮的类星体背景视线上偶然探测到一个红移为2.5、碰撞参数为50 kpc的0.2 L $^*$，Lyman-$α$发射星系。类星体的高解析度光谱显示出一个部分莱曼极限吸收系统（$N_\mathrm{HI}=10^{16.94\pm0.10}$ cm $^{-2}$），有许多与前景星系相同红移的相关金属吸收线。使用光电离模型，仔细对待测量误差和边缘化的电离辐射光谱的形状和归一化的不确定性，我们推导出的总氢柱密度$N_\mathrm{H}=10^{19.4\pm0.3}$厘米$^{-2}$，并表明，所有的吸收云金属富集，与$Z=0.1$ - $0.6 Z_\odot$。这些金属丰度和系统的大速度宽度（$436$ km $\,$ s $^{-1}$）表明气体是由外流风产生的。使用膨胀壳模型，我们估计质量流出率为$\sim5 M_\odot\,$年$^{-1}$。我们的光电离模型产生非常小的尺寸（$<$ 100-500 pc）的吸收云，我们认为这是典型的高柱密度吸收环星系介质（CGM）。考虑到这些小尺寸和极端的运动学，目前还不清楚这些团块如何在CGM中存活而不被流体动力学不稳定性破坏。小的云大小意味着，即使是最先进的宇宙学模拟需要超过$1000$倍的质量分辨率的改善，以解决相关的流体动力学冷气体在CGM。
