arXiv subjects

Tiit Sepp

Publications and source records attributed to Tiit Sepp.

3 recordsLinked to original sources

arXiv2021

The First Global e-Competition on Astronomy and Astrophysics

The first Global e-Competition on Astronomy and Astrophysics was held online in September-October 2020 as a replacement for the International Olympiad on Astronomy and Astrophysics, which was postponed due to the COVID-19 pandemic. Despite the short time available for organisation, 8 weeks, the competition was run successfully, with 325 students from over 42 countries participating with no major issues. The feedback from the participants was positive and reflects the ways in which such events can boost interest in astronomy and astronomy education. With online activities set to become more prevalent in the future, we present an overview of the competition process, the challenges faced, and some of the lessons learned, aiming to contribute to the development of best practices for organizing online competitions.

physics.ed-ph↗

arXiv2016

Simulations of Galaxy Cluster Collisions with a Dark Plasma Component

Dark plasma is an intriguing form of self-interacting dark matter with an effective fluid-like behavior, which is well motivated by various theoretical particle physics models. We aim to find an explanation for an isolated mass clump in the Abell 520 system, which cannot be explained by traditional models of dark matter, but has been detected in weak lensing observations. We performed N-body smoothed particle hydrodynamics simulations of galaxy cluster collisions with a two component model of dark matter, which is assumed to consist of a predominant non-interacting dark matter component and a 10-40 percent mass fraction of dark plasma. The mass of a possible dark clump was calculated for each simulation in a parameter scan over the underlying model parameters. In two higher resolution simulations shock-waves and Mach cones were observed to form in the dark plasma halos. By choosing suitable simulation parameters, the observed distributions of dark matter in both the Bullet Cluster (1E 0657-558) and Abell 520 (MS 0451.5+0250) can be qualitatively reproduced.

astro-ph.CO↗

arXiv2013

Galaxy structures - Groups, clusters and superclusters

We provide a brief summary of the history of galaxy structure studies. We also introduce several large-scale redshift surveys and summarize the most commonly used methods to identify the groups and clusters of galaxies. We present several catalogues of galaxy groups.These catalogues can be used to study the galaxy groups in different environments. We also consider the properties of superclusters of galaxies in the nearby Universe and describe the largest system of galaxies observed - the Sloan Great Wall.

astro-ph.CO↗