16.02.2023

Prof. Daniel Schaerer/ Prof. Andreas Zezas/ Dr. Konstantinos Kovlakas.

Green Pea and Bluberry galaxies meeting

The group of Dr. Jiri Svoboda is organizing a meeting with a focus on Green-Pea and Blueberry galaxies. These are low-redshift and local Universe dwarf, compact, and highly star-forming galaxies with unique properties while they are considered to be the best local analogs of early Universe galaxies. Three general talks will be given during the morning session of the seminar by Prof. Daniel Schaerer, Prof. Andreas Zezas, and Dr. Konstantinos Kovlakas. >> 10:00 -- 10:45: Daniel Schaerer, University of Geneva: "Insights on the Lyman continuum escape and the hardness of the ionizing spectra of compact star-forming galaxies". >> 10:45 – 11:30: Andreas Zezas, University of Crete: "The X-ray emission of galaxies in the context of their stellar populations". >> 11:30 -- 12:15: Konstantinos Kovlakas, Institute of Space Sciences/Barcelona: "Theoretical X-ray scaling relations and constraints on the X-ray output of distant galaxies".

11.04.2023

Michal Bílek

What is the origin of the different kinematic morphologies of early-type galaxies?

Early-type galaxies (i.e. elliptical and lenticular) are divided into slow and fast rotators according to the appearance of their maps of line-of-sight velocity. Fast rotators show clear ordered rotation, while slow are supported mostly by velocity dispersion. I will speak about our work on investigation of the origin of this diversity. Inspired by cosmological simulations, we assumed that galaxies first form as fast rotators and then mergers transform some of them to slow rotators. We investigated the correlations of a measure of rotational support with various properties of galaxies that are sensitive to mergers. These include stellar ages, the presence of tidal features, and kinematically distinct cores. Each of these parameters is sensitive to a different type of merger and has a different lifetime. The found correlations, or their lack, together with observations of high-redshift universe, are explained the easiest, if the rotation support of early-type galaxies was decreased by multiple minor wet mergers more than 10 Gyr ago.

25.04.2023

Sergey Popov

Magnetic field evolution of neutron stars: are there magnetars in binary systems?

In the talk I briefly discuss the present day view on the magnetic field evolution of neutron stars and its main observational appearance. Then, I focus on the possibility to find magnetars in binary systems of different kind. Possible candidates include accreting neutron stars (in particular, ultra luminous X-ray sources), gamma-ray sources, and fast radio bursts. I present a scenario in which the existence of a highly magnetized neutron star in a high-mass X-ray binary is possible at an age of a few million years.

04.05.2023

Dr. Paolo Serra

The MeerKAT Fornax Survey: ubiquitous HI tails and clouds in the Fornax cluster

I will show first science results from the MeerKAT Fornax Survey. Our goal is to perform a detailed study of the nearby Fornax galaxy cluster in order to understand how galaxies lose their cold gas and stop forming stars in low-mass clusters (Mvir < 1e+14 Msun). We are doing so through very deep (down to ~1e+18/cm^2) and high resolution (up to ~ 1kpc and 1 km/s) MeerKAT observations of HI gas in a 1x2 Mpc^2 region centred on Fornax. Our survey started in October 2020 and is now 50% complete. These first data focus on the central region of the Fornax cluster and reveal for the first time the ubiquitous presence of tails and clouds of HI. Some of the HI is clearly being removed from Fornax galaxies as they interact with one another, with the intra-cluster medium and/or with the large-scale gravitational potential. I will present a sample of galaxies with long, one-sided, star-less HI tails (of which only one was previously known) radially oriented within the cluster and with measurable internal velocity gradients. The properties of these tails represent the first unambiguous evidence of ram pressure shaping the distribution of HI in the Fornax cluster. I will also discuss additional results on the HI mass function and the HI content of dwarf galaxies in Fornax.

25.05.2023

Josefa Grossschedl

TBD