The Lyman alpha reference sample IV. Morphology at low and high redshift
The Lyman alpha reference sample IV. Morphology at low and high redshift
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DOI：
10.1051/0004-6361/201425053
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发表时间：
2015-01
影响因子：
6.5
通讯作者：
L. Guaita;J. Melinder;Matthew Hayes;G. Östlin;Juan Gonzalez;G. Micheva;G. Micheva;A. Adamo;J. Mas-Hesse;A. Sandberg;H. Otí-Floranes;D. Schaerer;D. Schaerer;A. Verhamme;E. Freeland;I. Orlitová;P. Laursen;J. Cannon;Florent Duval;T. Rivera-Thorsen;E. C. Herenz;D. Kunth;H. Atek;J. Puschnig;P. Gruyters;S. Pardy;S. Pardy
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文献类型：
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作者：
L. Guaita;J. Melinder;Matthew Hayes;G. Östlin;Juan Gonzalez;G. Micheva;G. Micheva;A. Adamo;J. Mas-Hesse;A. Sandberg;H. Otí-Floranes;D. Schaerer;D. Schaerer;A. Verhamme;E. Freeland;I. Orlitová;P. Laursen;J. Cannon;Florent Duval;T. Rivera-Thorsen;E. C. Herenz;D. Kunth;H. Atek;J. Puschnig;P. Gruyters;S. Pardy;S. Pardy
语境。 Ly α 光子在星系中的传输是一个复杂的过程，Ly α 光子设法逃离某些星系的条件仍在研究中。莱曼 α 参考样本 (LARS) 是 14 个本地恒星形成星系的样本，旨在详细研究 Ly α 并将其与静止框架紫外线和光发射联系起来。目标。为了识别低红移和高红移下 Ly α 发射体（LAE，EW(Ly α) > 20 埃的星系）的典型静止帧紫外和光学特性，我们研究了 LARS 星系的形态特性，特别是那些表现出强烈 Ly α 辐射的星系。方法。我们测量了连续体、Ly α 和 Ha 图像中的尺寸和形态参数。我们通过使用基尼系数与 M20 以及不对称性与浓度图来研究形态。然后，我们在类似于 2 和 5.7 的 z 处模拟 LARS 星系，执行相同的形态测量。我们还研究了当前深场观测中 LARS 星系的可探测性。将 LARS 内的 LAE 子样本 (LARS-LAE) 进行堆叠，以与在高红移下进行的堆叠研究进行比较。结果。 LARS 星系具有连续体尺寸、恒星质量和静止框架绝对星等，是当地宇宙中典型的莱曼断裂类似物，也类似于 2 < z < 3 恒星形成星系和大质量 LAE。 LARS的光学形态与合并系统、不规则或星爆星系之一一致。我们第一次量化了 Ly α 图像中的形态：即使星际介质的各种内在条件有利于 Ly α 光子的逃逸，LARS-LAE 在连续体中显得很小，而且它们的 Ly α 很紧凑。 LARS 星系在 Ly α 中往往比在静止框架 UV 中延伸得更广。这意味着 Ly α 光子通过在 LARS 星系的 HII 区域周围形成晕而逃逸。结论。 LARS-LAE Ly α 图像的堆栈在中心达到峰值，表明使星系成为 LAE 的条件往往会产生集中的表面亮度分布。另一方面，所有 LARS 星系的堆叠都更浅、更延伸。这可能是由尘埃和 HI 数量和分布的多样性引起的，这会产生更复杂、不均匀和扩展的轮廓，就像在莱曼断裂星系中观察到的那样，它可以对堆栈做出贡献。我们无法确定控制星系是否发出净正 Ly α 通量的单一形态特性。然而，LARS-LAE 具有与合并系统一致的连续特性。
Context. The transport of Ly alpha photons in galaxies is a complex process and the conditions under which Ly alpha photons manage to escape from certain galaxies is still under investigation. The Lyman alpha reference sample (LARS) is a sample of 14 local star-forming galaxies, designed to study Ly alpha in detail and relate it to rest-frame UV and optical emission. Aims. With the aim of identifying rest-frame UV and optical properties, which are typical of Ly alpha emitters (LAEs, galaxies with EW(Ly alpha) > 20 angstrom) at both low and high redshift, we investigated the morphological properties of the LARS galaxies, in particular the ones that exhibit intense Ly alpha radiation. Methods. We measured sizes and morphological parameters in the continuum, Ly alpha, and Ha images. We studied morphology by using the Gini coefficient vs. M20 and asymmetry vs. concentration diagrams. We then simulated LARS galaxies at z similar to 2 and 5.7, performing the same morphological measurements. We also investigated the detectability of LARS galaxies in current deep field observations. The subsample of LAEs within LARS (LARS-LAEs) was stacked to provide a comparison to stacking studies performed at high redshift. Results. LARS galaxies have continuum size, stellar mass, and rest-frame absolute magnitude typical of Lyman break analogues in the local Universe and also similar to 2 < z < 3 star-forming galaxies and massive LAEs. LARS optical morphology is consistent with the one of merging systems, and irregular or starburst galaxies. For the first time we quantify the morphology in Ly alpha images: even if a variety of intrinsic conditions of the interstellar medium can favour the escape of Ly alpha photons, LARS-LAEs appear small in the continuum, and their Ly alpha is compact. LARS galaxies tend to be more extended in Ly alpha than in the rest-frame UV. It means that Ly alpha photons escape by forming haloes around HII regions of LARS galaxies. Conclusions. The stack of LARS-LAE Ly alpha images is peaked in the centre, indicating that the conditions, which make a galaxy an LAE, tend to produce a concentrated surface brightness profile. On the other hand, the stack of all LARS galaxies is shallower and more extended. This can be caused by the variety of dust and HI amount and distribution, which produces a more complex, patchy, and extended profile, like the one observed for Lyman break galaxies that can contribute to the stack. We cannot identify a single morphological property that controls whether a galaxy emits a net positive Ly alpha flux. However, the LARS-LAEs have continuum properties consistent with merging systems.