Systematic variation of the stellar initial mass function in early-type galaxies.

Much of our knowledge of galaxies comes from analysing the radiation emitted by their stars, which depends on the present number of each type of star in the galaxy. The present number depends on the stellar initial mass function (IMF), which describes the distribution of stellar masses when the population formed, and knowledge of it is critical to almost every aspect of galaxy evolution. More than 50 years after the first IMF determination, no consensus has emerged on whether it is universal among different types of galaxies. Previous studies indicated that the IMF and the dark matter fraction in galaxy centres cannot both be universal, but they could not convincingly discriminate between the two possibilities. Only recently were indications found that massive elliptical galaxies may not have the same IMF as the Milky Way. Here we report a study of the two-dimensional stellar kinematics for the large representative ATLAS(3D) sample of nearby early-type galaxies spanning two orders of magnitude in stellar mass, using detailed dynamical models. We find a strong systematic variation in IMF in early-type galaxies as a function of their stellar mass-to-light ratios, producing differences of a factor of up to three in galactic stellar mass. This implies that a galaxy's IMF depends intimately on the galaxy's formation history.

How Children and Adolescents Perceive Their Coping With Home Learning in Times of COVID-19: A Mixed Method Approach.

With the COVID-19 pandemic, children and adolescents confronted a completely new learning situation. Instead of learning in class, they had to cope with home learning to achieve academically. This mixed-method study examines how children and adolescents in Germany perceive their coping success with home learning during the COVID-19 pandemic and how personal, school, family, and peer context factors relate to this self-perceived coping success. Quantitative data from an online survey of n=141 children (mage =10,8y) and n=266 adolescents (mage =15,2y; study 1) were used to analyze the questions with multiple regression analysis. With the qualitative data from 10 interviews with parents and their children (study 2), we examined the process of how school, family, and peer groups interact with students' way of coping with home learning. Quantitative data show that most children and adolescents perceived their coping with home learning as successful and that school joy before COVID-19, parental support, and available equipment during home learning are still relevant for children, and family climate, calm place to learn, and equipment during home learning are important for adolescents learning at home. Qualitative data show that students apply individual ways of coping with home learning, where family and peers have a vital role, especially when contact with teachers is limited. Quantitative data confirm the importance of family context for students' self-perceived coping success.