We use high signal-to-noise spectroscopy for a sample of 232 quiescent galaxies in the Shapley Supercluster, to investigate how their stellar populations depend on velocity dispersion, luminosity and stellar mass. The sample spans a large range in velocity dispersion (sigma from 30-300 km/s) and in luminosity (M_R from -18.7 to -23.2). Estimates of age, total metallicity (Z/H) and alpha-element abundance ratio (a/Fe) were derived from absorption-line analysis, using single-burst models. Age, Z/H and a/Fe are all correlated positively with velocity dispersion, but we also find significant residual trends with luminosity: at given sigma, the brighter galaxies are younger, less alpha-enriched, and have higher Z/H. At face value, these results might suggest that the stellar populations depend on stellar mass as well as on velocity dispersion. However, we show that the observed trends can be reproduced by models in which the stellar populations depend systematically only on sigma, and are independent of stellar mass Mstel. For age, the observed luminosity correlation arises because young galaxies are brighter, at fixed Mstel. For metallicity, the observed luminosity dependence arises because metal-rich galaxies, at fixed mass, tend also to be younger, and hence brighter. We find a good match to the observed luminosity correlations with Age ~ sigma^0.40, Z/H ~ sigma^0.35, a/Fe ~ sigma^0.20, where the slopes are close to those found when fitting traditional scaling relations. We conclude that the star formation and enrichment histories of galaxies are determined primarily by the depth of their gravitational potential wells. The observed residual correlations with luminosity do not imply a corresponding dependence on stellar mass.
Magnetic Fields in the Shapley Supercluster Core with POSSUM: Challenging Model Predictions
Universidad Complutense de Madrid（马德里康普顿斯大学）；Università degli Studi di Bologna（博洛尼亚大学）；INAF – Istituto di Radioastronomia（意大利国家天体物理研究所射电天文研究所）；The University of Chicago（芝加哥大学）；Dunlap Institute for Astronomy and Astrophysics, University of Toronto（多伦多大学邓普勒天文学与天体物理研究所）；The Australian National University（澳大利亚国立大学）；National Research Council Canada, Herzberg Research Centre for Astronomy and Astrophysics（加拿大国家研究委员会赫茨伯格天文学与天体物理研究中心）
Cosmic dance in the Shapley Concentration Core II. The uGMRT-MeerKAT view of filaments in the brightest cluster galaxies and tailed radio galaxies in the A3528 cluster complex
本文利用 uGMRT 和 MeerKAT 射电观测结合 eROSITA X 射线数据，研究沙普利超星系团核心 A3528 复合体，发现最亮团星系周围存在谱指数极陡的弥散射电纤维，并提出小型并合可重新加速射电星系等离子体。
Hidden Vela Supercluster Revealed by First Hybrid Redshift & Peculiar Velocity Reconstruction
Université Claude Bernard Lyon 1（里昂第一大学）；Research School of Astronomy and Astrophysics, Australian National University（澳大利亚国立大学天体物理学与天文学研究学院）；Department of Astronomy, University of Cape Town（开普敦大学天文学系）；Centre for Astrophysics & Supercomputing, Swinburne University（斯威本大学天体物理与超级计算中心）；ARC Centre of Excellence for Dark Matter Particle Physics（ARC暗物质粒子物理卓越研究中心）；INAF Osservatorio Astronomico di Cagliari（意大利国家天体物理研究所卡利亚里天文台）
