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arXiv 2008.01731astro-ph.GA
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用MUSE揭示了CR7的性质:z=6.6时为扩展Lyman- $α$发射提供动力的年轻星暴

The nature of CR7 revealed with MUSE: a young starburst powering extended Lyman-$α$ emission at z=6.6

Jorryt Matthee, Gabriele Pezzulli, Ruari Mackenzie, Sebastiano Cantalupo, Haruka Kusakabe, Floriane Leclercq, David Sobral, Johan Richard, Lutz Wisotzki, Simon … 展开作者

Jorryt Matthee, Gabriele Pezzulli, Ruari Mackenzie, Sebastiano Cantalupo, Haruka Kusakabe, Floriane Leclercq, David Sobral, Johan Richard, Lutz Wisotzki, Simon Lilly, Leindert Boogaard, Raffaella Marino, Michael Maseda, Themiya Nanayakkara

摘要:

CR 7是在$z = 6.6$已知的最发光的莱曼- $α$发射体(LAE)之一,并且由至少三个被莱曼- $α$(Ly $α$)发射包围的UV组分组成。以前的研究表明,它可能拥有极端电离源。在这里,我们提出了深积分场光谱的CR 7与VLT/MUSE。我们在$z\approx5$测量了具有与典型LAEs相似的晕尺度长度的扩展发射。CR 7的Ly $α$晕沿连接多个组件的方向明显拉长,可能追踪了下面的气体分布。的Ly $α$发射起源几乎完全从最亮的紫外线分量,但我们也确定了一个微弱的运动学不同的Ly $α$发射区域附近的一个较暗的组件。结合新的近红外数据,MUSE数据表明,静止帧Ly $α$等效宽度(EW)为$\approx100$ × 10。这比具有仔细匹配的Ly $α$轮廓(因此可以说HI柱密度)的低红移类似物中测量的EW高出四倍,但这种EW似乎可以用恒星形成来解释。与其他Ly $α$团块中的活动星系核相比,Ly $α$光谱更窄、更陡,红外与紫外比更小,因此需要活动星系核供电的替代方案也不受欢迎。CR 7的Ly $α$发射虽然非常明亮,但在较低的红移下与更常见的LAE发射非常相似,并且可能是由年轻的贫金属星暴提供动力。

英文摘要:

CR7 is among the most luminous Lyman-$α$ emitters (LAEs) known at $z = 6.6$ and consists of at least three UV components that are surrounded by Lyman-$α$ (Ly$α$) emission. Previous studies have suggested that it may host an extreme ionising source. Here, we present deep integral field spectroscopy of CR7 with VLT/MUSE. We measure extended emission with a similar halo scale length as typical LAEs at $z\approx5$. CR7's Ly$α$ halo is clearly elongated along the direction connecting the multiple components, likely tracing the underlying gas distribution. The Ly$α$ emission originates almost exclusively from the brightest UV component, but we also identify a faint kinematically distinct Ly$α$ emitting region nearby a fainter component. Combined with new near-infrared data, the MUSE data show that the rest-frame Ly$α$ equivalent width (EW) is $\approx100$ Å. This is a factor four higher than the EW measured in low-redshift analogues with carefully matched Ly$α$ profiles (and thus arguably HI column density), but this EW can plausibly be explained by star formation. Alternative scenarios requiring AGN powering are also disfavoured by the narrower and steeper Ly$α$ spectrum and much smaller IR to UV ratio compared to obscured AGN in other Ly$α$ blobs. CR7's Ly$α$ emission, while extremely luminous, resembles the emission in more common LAEs at lower redshifts very well and is likely powered by a young metal poor starburst.

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