成熟但仍在成长：JWST探测z ~ 2时最早的星团光
Mature but Still Growing: JWST Detection of the Earliest Intracluster Light at z ~ 2
AI总结：
JWST探测到z ~ 2时最早的星团内光，揭示其在大质量暗物质晕中早期形成并具有动态信息。
摘要：
我们呈现了利用JWST对XLSSC 122中在z=1.98处的星团内光（ICL）进行分析的结果，该系统目前是已知最远的强引力透镜星系团，其成员群体已发展成熟。利用深入的JWST成像数据配合哈勃空间望远镜（HST）数据，并仔细控制系统误差，我们稳健地探测到从最亮星系（BCG）向外延伸数百千-parsec的弥散发射，其亮度达到约29 mag arcsec^-2。多组分PSF卷积的Sersic建模将表面亮度分布分离为三个组成部分：BCG核心、BCG包层和ICL组成部分，其Sersic指数在不同波长下保持稳定。几乎平坦的颜色剖面表明BCG包层和ICL的恒星群体在径向上的变化极小。在七个波段上测量的ICL占比约为17%，证明在z约2时，大质量暗物质晕中星团内恒星的积累已基本完成。ICL占比在5000埃的固有帧下达到峰值，表现出与动态活跃星团观察到的行为相似。我们还探测到相对于最佳拟合Sersic模型的南侧ICL过剩，并利用小波基建模量化了这一现象，提供了进一步证据表明该系统处于动态活跃状态。BCG + ICL光分布和强引力透镜质量图在约100 kpc范围内显示出强烈的形态一致性。这些发现确立了ICL作为大质量暗物质晕中早期形成且动态信息丰富的组成部分。
英文摘要：
We present a JWST analysis of intracluster light (ICL) in XLSSC 122 at z = 1.98, currently the most distant known strong lensing galaxy cluster with an evolved member population. Using deep JWST imaging complemented by HST data and careful control of systematics, we robustly detect diffuse emission extending to several hundred kpc from the brightest cluster galaxy (BCG) down to about 29 mag arcsec^-2. Multi component PSF convolved Sersic modeling separates the surface brightness profiles into three components: a BCG core, a BCG envelope, and an ICL component, with stable Sersic indices across wavelengths. Nearly flat color profiles indicate minimal radial variation in the stellar populations of the BCG envelope and the ICL. The median ICL fraction measured across seven bands is about 17 percent, demonstrating that the buildup of intracluster stars in massive halos was already well underway by z about 2. The ICL fraction peaks near 5000 Angstrom in the rest frame, resembling the behavior observed in dynamically active clusters. We also detect a southern excess of ICL relative to the best fit Sersic model and quantify it using wavelet based modeling, providing additional support that this system is dynamically active. The BCG + ICL light distribution and strong lensing mass map show strong morphological agreement within about 100 kpc. These findings establish the ICL as an early forming and dynamically informative component of massive halos.
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