AI 中文总结
本研究利用IllustrisTNG300模拟，探究结合外围恒星质量与渗流方法缓解星系团选择的卫星污染，可获得高完备性与纯度的大质量星系团样本，提供了可靠的星系团选择方案。
AI 中文摘要
星系团的数量是一种强大的宇宙学探针，但光学星系团宇宙学受限于选择系统误差，尤其是对基于星系群体（如红序星系）的星系团 finder 产生影响的投影效应。星系中心星系的外围恒星质量（$M_\text{out}$，即50-100千秒差距环带内的恒星质量）提供了一种仅依赖中心星系的替代选择方式，因此在很大程度上不受投影效应影响。不过它的主要系统误差是卫星星系污染，因为大质量星系团可能拥有不止一个具有高外围恒星质量的星系。我们利用$z=0.4$处的IllustrisTNG300模拟，量化了这种污染情况，并研究了一种基于邻近性的简单渗流方法来缓解该问题，该方法会移除样本中位于质量更大星系的给定半径范围内、外围恒星质量较低的星系。我们发现，即使不使用渗流，由朋友-朋友（FoF）算法定义的卫星星系占比也较小（对于$M_\text{out} > 10^{10}\text{M}_\text{\textodot}$，该占比≤15%；对于$M_\text{out} > 10^{11}\text{M}_\text{\textodot}$，占比<10%），且渗流可进一步降低该占比，当渗流半径增大至$3.0R_{200c}$时，改善效果会增强。对于中等偏高的外围恒星质量阈值（约$4\times10^{10}\text{M}_\text{\textodot}$）和渗流半径（约$2.0R_{200c}$），我们能获得一个对晕质量$\text{≥}10^{14}\text{M}_\text{\textodot}$的星系团样本，兼具高完备性与高纯度。这些结果表明，外围恒星质量结合简单渗流方法，有望为大质量星系团提供一种干净且易于校准的选择方式。
英文摘要
The abundance of galaxy clusters is a powerful cosmological probe, but optical cluster cosmology is limited by selection systematics, in particular the projection effects that affect cluster finders based on galaxy populations such as the red sequence. The outer stellar mass ($M_\mathrm{out}$) of cluster central galaxies -- e.g., the stellar mass in a 50-100 kpc annulus -- offers an alternative selection that relies only on the central galaxy and is therefore largely free from projection effects. Its primary systematic is instead satellite contamination, since massive clusters can host more than one galaxy with high outer stellar mass. Using the IllustrisTNG300 simulation at $z=0.4$, we quantify this contamination and investigate a simple, proximity-based percolation method to mitigate it, in which galaxies with lower outer stellar mass lying within a given radius of a more massive galaxy are removed from the sample. We find that the satellite fraction defined by the friends-of-friends (FoF) algorithm is modest even without percolation ($\leq 15\%$ for $M_\mathrm{out} > 10^{10}\,\mathrm{M}_\odot$ and $<10\%$ for $M_\mathrm{out} > 10^{11}\,\mathrm{M}_\odot$), and that percolation reduces it further, with the improvement increasing for percolation radii up to $3.0\,R_{200c}$. For a moderately high outer stellar mass cut ($\sim 4\times10^{10}\,\mathrm{M}_\odot$) and percolation radius ($\sim 2.0\,R_{200c}$), we recover a cluster sample that is both highly complete and pure for halo masses $\gtrsim 10^{14}\,\mathrm{M}_\odot$. These results indicate that outer stellar mass, combined with simple percolation, has the potential to provide a clean and readily calibratable selection of massive galaxy clusters.
Comments7 pages, 6 figures, to be submitted to the Open Journal of Astrophysics
