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arXiv · 1303.0027

Physical Properties of Spectroscopically-Confirmed Galaxies at z >= 6. II. Morphology of the Rest-Frame UV Continuum and Lyman-alpha Emission

Linhua Jiang·Eiichi Egami·Xiaohui Fan·Rogier A. Windhorst·Seth H. Cohen·Romeel Dave·Kristian Finlator·Nobunari Kashikawa·Matthew Mechtley·Masami Ouchi·Kazuhiro Shimasaku
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Abstract

We present a detailed structural and morphological study of a large sample of spectroscopically-confirmed galaxies at z >= 6, using deep HST near-IR broad-band images and Subaru optical narrow-band images. The galaxy sample consists of 51 Lyman-alpha emitters (LAEs) at z ~ 5.7, 6.5, and 7.0, and 16 Lyman-break galaxies (LBGs) at 5.9 < z < 6.5. These galaxies exhibit a wide range of rest-frame UV continuum morphology in the HST images, from compact features to multiple component systems. The fraction of merging/interacting galaxies reaches 40% ~ 50% at the brightest end of M_1500 <= -20.5 mag. The intrinsic half-light radii r_{hl,in}, after correction for PSF broadening, are roughly between r_{hl,in} ~ 0.05" (0.3 kpc) and 0.3" (1.7 kpc) at M_1500 <= -19.5 mag. The median r_{hl,in} value is 0.16" (~0.9 kpc). This is consistent with the sizes of bright LAEs and LBGs at z >= 6 in previous studies. In addition, more luminous galaxies tend to have larger sizes, exhibiting a weak size-luminosity relation r_{hl,in} \propto L^{0.14} at M_1500 <= -19.5 mag. The slope of 0.14 is significantly flatter than those in fainter LBG samples. We discuss the morphology of z >= 6 galaxies with nonparametric methods, including the CAS system and the Gini and M_20 parameters, and demonstrate their validity through simulations. We search for extended Lyman-alpha emission halos around LAEs at z ~ 5.7 and 6.5, by stacking a number of narrow-band images. We do not find evidence of extended halos predicted by cosmological simulations. Such Lyman-alpha halos, if they exist, could be weaker than predicted. Finally, we investigate any positional misalignment between UV continuum and Lyman-alpha emission in LAEs. While the two positions are generally consistent, several merging galaxies show significant positional differences. This is likely caused by a disturbed ISM distribution due to merging activity.

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Linhua Jiang, Eiichi Egami, Xiaohui Fan, Rogier A. Windhorst, Seth H. Cohen, Romeel Dave, Kristian Finlator, Nobunari Kashikawa, Matthew Mechtley, Masami Ouchi, Kazuhiro Shimasaku. 2013-02-28. Physical Properties of Spectroscopically-Confirmed Galaxies at z >= 6. II. Morphology of the Rest-Frame UV Continuum and Lyman-alpha Emission. https://doi.org/10.1088/0004-637x/773/2/153

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