Title: Intracluster light is already abundant at redshift beyond unity Show Chinese title

Title: 团内光在红移超过一的情况下已经很丰富了

Abstract: Intracluster light (ICL) is diffuse light from stars that are gravitationally bound not to individual member galaxies, but to the halo of galaxy clusters. Leading theories predict that the ICL fraction, defined by the ratio of the ICL to the total light, rapidly decreases with increasing redshift, to the level of a few per cent at z > 1. However, observational studies have remained inconclusive about the fraction beyond redshift unity because, to date, only two clusters in this redshift regime have been investigated. One shows a much lower fraction than the mean value at low redshift, whereas the other possesses a fraction similar to the low-redshift value. Here we report an ICL study of ten galaxy clusters at 1 \lesssim z \lesssim 2 based on deep infrared imaging data. Contrary to the leading theories, our study finds that ICL is already abundant at z \lesssim 1, with a mean ICL fraction of approximately 17\%. Moreover, no significant correlation between cluster mass and ICL fraction or between ICL color and cluster-centric radius is observed. Our findings suggest that gradual stripping can no longer be the dominant mechanism of ICL formation. Instead, our study supports the scenario wherein the dominant ICL production occurs in tandem with the formation and growth of the brightest cluster galaxies and/or through the accretion of preprocessed stray stars. Show Chinese abstract

Abstract: 星团内的弥散光（ICL）来自那些引力上不属于个别成员星系而是属于星团晕的恒星发出的弥散光。主导理论预测，由ICL与总光比值定义的ICL分数随着红移的增加迅速下降，在z > 1时降至百分之几的水平。然而，由于迄今为止只有两个处于这一红移范围内的星团被研究过，观测研究对于红移超过一的ICL分数仍然没有定论。其中一个显示的分数远低于低红移时的平均值，而另一个则与低红移时的值相当。在这里，我们报告了基于深红外成像数据对十个红移范围在1 \lesssim z \lesssim 2的星团进行的ICL研究。与主导理论相反，我们的研究表明，ICL在z \lesssim 1时已经非常丰富，其平均ICL分数约为17%。此外，我们没有观察到星团质量与ICL分数之间或ICL颜色与星团中心距离之间的显著相关性。我们的发现表明，渐进剥离不再可能是ICL形成的主要机制。相反，我们的研究支持这样一种情景：即主要的ICL产生与最亮星团星系的形成和增长同步发生，或者通过预先处理过的游离恒星的吸积来实现。