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arXiv 2007.01322astro-ph.GA
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VIMOS超深探测:$2 < z < 6$处Ly PDMATHAAB发射线形态

The VIMOS Ultra-Deep Survey: the Ly$α$ emission line morphology at $2 < z < 6$

B. Ribeiro, O. Le Fèvre, A. Paulino-Afonso, P. Cassata, V. Le Brun, B. C. Lemaux, D. Maccagni, L. Pentericci, R. Thomas, G. Zamorani, E. Zucca, R. Amorín, S. Ba… 展开作者

B. Ribeiro, O. Le Fèvre, A. Paulino-Afonso, P. Cassata, V. Le Brun, B. C. Lemaux, D. Maccagni, L. Pentericci, R. Thomas, G. Zamorani, E. Zucca, R. Amorín, S. Bardelli, L. P. Cassarà, L. Guaita, N. P. Hathi, A. Koekemoer, D. Schaerer, M. Talia, J. Pforr, L. Tresse, S. Fotopoulou, D. Vergani

摘要:

Lyman- $α$(Ly $α$)发射线已被广泛用于确认和研究高红移星系。我们报告的线形态中看到的二维光谱从VIMOS超深巡天的样本中的914 Ly $α$发射器从4192恒星形成星系的母样本在$2<z_\mathrm{spec}\lesssim6$。通过对Ly $α$辐射空间范围的研究,可以深入了解星系中Ly $α$光子的逃逸过程。我们将线发射分类为不存在的,重合的,投影的空间偏移,或相对于观察到的2D UV连续发射扩展。在我们的样本中的线发射器被分类为约45%的一致,约24%的扩展和约11%的偏移发射器。对于检测到的紫外线连续的星系,我们表明,扩展的Ly $α$发射器(LAES)对应于最高的等效宽度星系(平均$W_\mathrm{Lyα}\sim-22$)。这意味着这类对象在窄带选择样本中最常见,这些样本通常选择高等效宽度LAE,即$<-20$。扩展Ly $α$发射器被认为是质量较小,恒星形成较少,尘埃含量较低,和较小的紫外线连续谱的大小($r_{50}\sim0.9$千秒差距)的所有类在这里考虑。我们还发现,具有较大的UV-尺寸的星系有较低的分数的Ly $α$发射器。通过对不同发射体光谱的叠加,我们发现较弱的Ly $α$发射体具有较强的低电离星际介质(ISM)吸收线。有趣的是,我们发现,星系与Ly $α$偏移发射(中位数分离$1.1_{-0.8}^{+1.3}$ kpc的紫外连续)显示类似的速度偏移在ISM中的可见光发射(和不同的其他Ly $α$发射类)。这类天体可能暗示着气体吸积、明亮的偏移团块或正在进行的合并活动进入更大的星系。

英文摘要:

The Lyman-$α$ (Ly$α$) emission line has been ubiquitously used to confirm and study high redshift galaxies. We report on the line morphology as seen in the 2D spectra from the VIMOS Ultra Deep Survey in a sample of 914 Ly$α$ emitters from a parent sample of 4192 star-forming galaxies at $2<z_\mathrm{spec}\lesssim6$. The study of the spatial extent of Ly$α$ emission provides insight into the escape of Ly$α$ photons from galaxies. We classify the line emission as either non-existent, coincident, projected spatial offset, or extended with respect to the observed 2D UV continuum emission. The line emitters in our sample are classified as ~45% coincident, ~24% extended and ~11% offset emitters. For galaxies with detected UV continuum, we show that extended Ly$α$ emitters (LAEs) correspond to the highest equivalent width galaxies (with an average $W_\mathrm{Lyα}\sim-22$Å). This means that this class of objects is the most common in narrow-band selected samples, which usually select high equivalent width LAEs, $<-20$Å. Extended Ly$α$ emitters are found to be less massive, less star-forming, with lower dust content, and smaller UV continuum sizes ($r_{50}\sim0.9$kpc) of all the classes considered here. We also find that galaxies with larger UV-sizes have lower fractions of Ly$α$ emitters. By stacking the spectra per emitter class we find that the weaker Ly$α$ emitters have stronger low ionization inter-stellar medium (ISM) absorption lines. Interestingly, we find that galaxies with Ly$α$ offset emission (median separation of $1.1_{-0.8}^{+1.3}$kpc from UV continuum) show similar velocity offsets in the ISM as those with no visible emission (and different from other Ly$α$ emitting classes). This class of objects may hint at episodes of gas accretion, bright offset clumps, or on-going merging activity into the larger galaxies.

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