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

Scheduled seminars

Beyond blobs: dissecting extreme, dusty starbursts on (k)pc-scales

Matúš Rybák

Sub-millimeter galaxies (SMGs) play a key role in the early the Universe and are an important laboratory for understanding intense star formation. However, our understanding of SMGs -- what drives their intense star-formation? what are the physical properties of their star-forming ISM? - requires high angular resolution, long unavailable in mm/FIR wavelengths. The start of ALMA operations in 2011 was a quantum leap from barely resolved SMGs to kpc-scales studies, matching or even exceeding the resolution achieved for present-day galaxies. A further order-of-magnitude jump in resolution - to parcsec scales - and sensitivity has been provided by strong gravitational lensing. I will showcase recent results from resolved multi-tracer (FIR, CO, C+) studies of dust and gas in z>2 SMGs at (k)pc resolution. Combining the superb angular resolution and high-frequency capabilities of ALMA, gravitational lensing and radiative transfer modelling, our results provide an unprecedented view of the conditions in these extreme star factories down to 50-pc scales

Location: Spořilov, místnost 101

A system of linear algebraic equations for the long-time mean velocities of fluid in stationary turbulence

Martin Macháček

First we transform the Navier-Stokes equations into a strictly equivalent but simpler dynamical system and show some of its applications. Then we examine the case of stationary turbulence and in a mathematically rigorous way derive a system of linear algebraic equations for long time mean values of fluid velocity at diffferent points and of their product, e. g. <v(x)>, <v(x) v(x')>, <v(x) v(x') v(x'')> etc.

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

Particle-In-Cell, a numerical method at the border between astrophysics and laboratory experiments

Quentin Moreno

The modern age of physics is to a large degree determined by the availability of high speed and high capacity computer systems. The use of these computing facilities for performing numerical experiments on collisionless plasmas covers now almost half a century of experience. Many problems in plasmas and in particular space plasma physics with their enormous complexity could not have been solved or even tackled without computers and numerical simulations. The latter must accompany observations and experiments in order to understand what is going on in such non-linear plasma physics. A brief discussion about numerical methods is therefore not only unavoidable but even necessary. Thus far, two kinetic numerical approaches are commonly used in the plasma physics community to study collisionless plasma processes. The Vlasov approach based on an Eulerian scheme is one of them. The code performs a direct integration of the Vlasov-Maxwell system of equations discretized on a phase-space grid. Another approach is the Particle-In-Cell method (PIC) using a Lagrangian-Eulerian approach, where the distribution function of each species is formed by a collection of computational particles (CPs), and Maxwell’s equations are solved on an Eulerian grid. Such codes can be used to excite linear plasma modes and nonlinear plasma dynamics can be followed. Our presentation is dedicated to PIC simulation code and is structured as follows. We outline the principle upon which a PIC code is based in a first part, and we summarize the numerical Yee leap-frog scheme. A second part is dedicated to present the Open Source simulation code SMILEI, where examples will be illustrate in a third part.

Location: Sporilov, mistnot 101

Software Engineering at LBTO

Petr Kubánek

Large Binocular Telescope Observatory (LBTO) is one of the largest currently operating telescope on the planet (and the largest one in continental USA). Boasting two 8.4m Richard F. Caris Mirror Lab honeycomb mirrors, perched atop Mount Graham in Southeast Arizona, it comes equipped with the state of the art sensors and actuators. Thanks to its partly experimental design, the telescope has adaptive optics secondary mirrors, multiple focal stations and a growing list of instruments. In this talk I will focus on design of the software to run the observatory. Staring from the low level hardware interfaces, I will progress towards the upper layer used by observers to control the observations. I will as well describe some of the science done with its instruments, as well as some of the unique observations achieved by this complex instrument.

Location: Sporilov 101

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