How did the dwarf galaxy population of present-day galaxy clusters form and grow over time? We address this question by analysing the history of dark matter subhaloes in the Millennium-II cosmological simulation. A semi-analytic model serves as the link to observations. We argue that a reasonable analogue to early morphological types or red-sequence dwarf galaxies are those subhaloes that experienced strong mass loss, or alternatively those that have spent a long time in massive haloes. This approach reproduces well the observed morphology-distance relation of dwarf galaxies in the Virgo and Coma clusters, and thus provides insight into their history. Over their lifetime, present-day late types have experienced an amount of environmental influence similar to what the progenitors of dwarf ellipticals had already experienced at redshifts above two. Therefore, dwarf ellipticals are more likely to be a result of early and continuous environmental influence in group- and cluster-size haloes, rather than a recent transformation product. The observed morphological sequences of late-type and early-type galaxies have developed in parallel, not consecutively. Consequently, the characteristics of today's late-type galaxies are not necessarily representative for the progenitors of today's dwarf ellipticals. Studies aiming to reproduce the present-day dwarf population thus need to start at early epochs, model the influence of various environments, and also take into account the evolution of the environments themselves.
Model-Independent Indication for a Localized Anomaly in the Late-Time Expansion History
Centre for Theoretical Physics, Jamia Millia Islamia（贾米阿·米利娅伊斯兰大学理论物理中心）；Indian Institute of Astrophysics（印度天体物理研究所）；Korea Astronomy and Space Science Institute (KASI)（韩国天文与空间科学研究所）；School of Mathematical and Physical Sciences, University of Sheffield（谢菲尔德大学数学与物理科学学院）
Reionization of the Milky Way, M31, and their satellites I: reionization history and star formation
对银河系（MW）、M31及其附近的本星系群（LG）的观测可以提供有关再电离源的线索。我们提出了一套辐射转移模拟的基础上提供的约束本地UniversE模拟（CLUES）项目，旨在重建本地宇宙，包括一个现实的MW-M31对和附近的室女座的初始条件。我们的盒子大小（91兆秒差距）是足够大的，以纳入电离光子的LG的相关来源。我们采用了一系列的源模型，模仿辐射反馈之间的暗物质晕$10^{8}-10^{9}$ M $_{\odot}$的潜在影响。虽然LG主要是以由内而外的方式再电离，但其电离的最后40%显示出一些外部影响。对于LG卫星，我们没有发现证据表明它们的再电离红移与卫星的现今质量或与中央星系的距离有关。我们发现，不到20%的MW和M31卫星在全球再电离结束之前经历了任何恒星形成。这些卫星中大约有5%可以归类为化石，这意味着大多数恒星形成都发生在这些早期。更大质量的卫星在全球再电离结束之前有更多的累积恒星形成，但分散是显着的，特别是在低质量端。现今的质量和与中央星系的距离对于卫星星系中是否存在古老的恒星星族是很难预测的。
Observations of SN 2015F suggest a correlation between the intrinsic luminosity of Type Ia supernovae and the shape of their light curves >900 days after explosion
