The large- and small-scale properties of the intergalactic gas in the Slug Ly α nebula revealed by MUSE He II emission observations
The large- and small-scale properties of the intergalactic gas in the Slug Ly α nebula revealed by MUSE He II emission observations
复制标题
DOI：
10.1093/mnras/sty3481
复制
发表时间：
2019-03-01
影响因子：
4.8
通讯作者：
Prochaska, J. Xavier
中科院分区：
文献类型：
--
作者：
Cantalupo, Sebastiano;Pezzulli, Gabriele;Prochaska, J. Xavier
在z接近或等于2.3的情况下，预计大小约为450kpc的Ly Alpha星云，是一个罕见的在发射方面研究宇宙网中星系间气体性质的实验室。自从它被发现以来，这种鼻涕虫一直是几个光谱后续研究的对象，以限制发射气体的性质。在这里，我们报告了深缪斯积分场光谱搜索的结果，非共振，扩展的He II波长1640和金属发射。扩展的He II辐射在大约100kpc的尺度上被探测到，但只在与明亮的Lyα发射和连续谱探测到的源有关的一些区域中，这意味着在投影空间中相邻区域的线比发生了巨大而突然的变化。最近探测到的相关Hα发射和Lyα运动学中类似的突变，强烈地表明He II/Lyα梯度是由于相关类星体与这些区域之间的物理距离的巨大变化所致。这意味着发射结构的总长度可以延伸到物理MPC尺度，并且主要沿我们的视线定向。与此同时，相对较低的He II/Lyα值表明，发射气体具有广泛的密度分布，如果用对数正态表示，这意味着色散程度与星际星系介质中预期的色散程度一样高。这些结果强化了这样一种可能性，即星际气体在高红移时的密度分布在低于我们目前观测的几个物理kpc的空间分辨率的尺度上是极其块状和多相的。
With a projected size of about 450 kpc at z similar or equal to 2.3, the Slug Ly alpha nebula is a rare laboratory to study, in emission, the properties of the intergalactic gas in the Cosmic Web. Since its discovery, the Slug has been the subject of several spectroscopic follow-ups to constrain the properties of the emitting gas. Here we report the results of a deep MUSE integral-field spectroscopic search for non-resonant, extended He II lambda 1640 and metal emission. Extended He II radiation is detected on scales of about 100 kpc, but only in some regions associated with the bright Ly alpha emission and a continuum-detected source, implying large and abrupt variations in the line ratios across adjacent regions in projected space. The recent detection of associated H alpha emission and similar abrupt variations in the Ly alpha kinematics, strongly suggest that the He II/Ly alpha gradient is due to large variations in the physical distances between the associated quasar and these regions. This implies that the overall length of the emitting structure could extend to physical Mpc scales and be mostly oriented along our line of sight. At the same time, the relatively low He II/Ly alpha values suggest that the emitting gas has a broad density distribution that - if expressed in terms of a lognormal - implies dispersions as high as those expected in the interstellar medium of galaxies. These results strengthen the possibility that the density distribution of intergalactic gas at high redshift is extremely clumpy and multiphase on scales below our current observational spatial resolution of a few physical kpc.