Seminars

Seminars take place in the lecture room of the Spořilov building (see contacts) unless noted otherwise.

Scheduled seminars

Radio-Active CoWS: Probing the Role of Environment on Radio-AGN at z~1 with MaDCoWS

Emily Moravec

AGN properties and dense environments are connected in a myriad of ways. For galaxies, the hot gas found in dense environments can impact AGN fueling and confine AGN outflows. Meanwhile, feedback from AGN jets can have a significant mechanical and thermal impact upon the surrounding gas. To better understand the interplay between AGN and the hot intracluster medium in galaxy clusters, we have been investigating the distribution of AGN and properties of the AGN population associated with z~1 galaxy clusters from the Massive and Distant Clusters of WISE Survey (MaDCoWS). I will first give an overview of MaDCoWS, which is the first cluster survey capable of discovering massive clusters at these redshifts over the full extragalactic sky, and will discuss key results from this program. I will then focus upon our studies of the AGN population. I will first discuss the distribution of AGN relative to the clusters. Then, I will present the results from a study with the JVLA to determine the radio morphologies of extended radio sources and the properties of their host-galaxies in a sub-sample of ~50 MaDCoWS clusters. Using optical, infrared, and radio data, we investigate correlations between the size and luminosity of the radio-AGN with stellar mass, cluster-centric radius, and cluster richness. We find a remarkable diversity of radio galaxy and host galaxy properties across a range of cluster properties.

Location: mistnost 101 Sporilov

Joint journal club

Tiina Liments and Boris Deshev

Tiina Limets will present paper: Bujarrabal et al. 2018, A&A, 616, L3 "High-resolution observations of the symbiotic system R Aqr. Direct imaging of the gravitational effects of the secondary on the stellar wind" https://ui.adsabs.harvard.edu/abs/2018A%26A...616L...3B/abstract and Boris Deshev will present paper: by Zhang et al. (2019), submitted "On The Effect of Environment on Line Emission from the Circumgalactic Medium" https://ui.adsabs.harvard.edu/abs/2019arXiv190601643Z/abstract

Location: Sporilov 101

Rare event searches: looking for dark matter and new neutrino physics

Lucie Tvrzníková

In this talk, I will present a high-level overview of my work: In the first half, I will focus on direct dark matter (DM) searches and R&D efforts for the next generation of xenon time projection chambers. The nature of DM remains a mystery since it has so far eluded detection in the laboratory. The Large Underground Xenon (LUX) experiment was built to observe the interaction of DM with xenon target nuclei. LUX acquired data from April 2013 to May 2016 at the Sanford Underground Research Facility in Lead, South Dakota, which led to publications of many world-leading exclusion limits that probe much of the unexplored DM parameter space. I will discuss the results from the LUX detector with a focus on sub-GeV dark matter, the status of the next-generation detector known as LZ, and R&D efforts on high voltage characterization in liquid argon and xenon to enable future detector design. In the second part of my talk, I will focus on neutrino experiments trying to answer questions that will open the door to physics beyond the Standard Model: whether neutrinos are their own antiparticles and what is the effective mass of the electron antineutrino m_ve. This effective mass can be determined from a sufficiently high-precision measurement of the tritium beta-decay spectrum around its endpoint. I will introduce the Project 8 experiment, which is using the Cyclotron Radiation Emission Spectroscopy (CRES) technique to perform a radio-frequency-based measurement of the decay electron energy. To achieve its goal sensitivity of m_ve 40 meV, Project 8 will use an atomic tritium source to eliminate rotational and vibrational excitations of molecular tritium that perturb the tritium spectrum endpoint. I will discuss the recent efforts toward atomic tritium at Lawrence Livermore National Lab. Lastly, I will also discuss R&D efforts to characterize SeF6 to evaluate its effectiveness as a neutrinoless double-beta decay detector target.

Location: Sporilov, mistnost 101

Testing general relativity using X-ray reflection spectroscopy

Cosimo Bambi

Einstein's theory of general relativity was proposed over 100 years ago and has successfully passed a large number of observational tests in weak gravitational fields. However, the strong field regime is still largely unexplored, and there are many modified and alternative theories that have the same predictions as Einstein's gravity for weak fields and present deviations only when gravity becomes strong. X-ray reflection spectroscopy is potentially a powerful tool for testing the strong gravity region around astrophysical black holes with electromagnetic radiation. In this talk, I will present the reflection model RELXILL_NK designed for testing the metric around black holes and the current constraints on possible new physics from the analysis of a few sources.

Location: Sporilov, mistnost 101

If you would like to give a seminar, please contact Georgios Loukes-Gerakopoulos or Vladimír Karas.

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