Wednesday Colloquium


"Phase-space structures of dark matter haloes"

Michał Maciejewski (MPA, Garching)


"Some unsolved problems in particle physics and cosmology"

Krzysztof Meissner (Institute of Theoretical Physics, Warsaw University)

I will discuss some fundamental problems in particle physics and cosmology that despite sometimes monumental effort remain unsolved. I will present my personal judgment on the insight gained so far and the proposed ways


"Chandra weakest sources - the ultimate limit"

Andrzej Sołtan (Copernicus Astronomical Centre, Warsaw)

A novel method to investigate a population of the weakest X-ray sources is presented. A Nearest Neighbor STatistics (NNST) is used to search for irregularities of the count distribution in the deep X-ray exposures. The formulae linking the number source counts with the NNST are derived. The NNST is applied to assess the source counts below the standard threshold of the discrete source detection.


"Properties of Milky Way globular clusters"

Janusz Kałużny (Copernicus Astronomical Centre, Warsaw)

General review of properties of Milky Way globular clusters will be followed by presentation of recent results based on HSTACS and ground based observations. Some new findings about extragalactic globular cluster will be also reported.


"Blue stragglers"

Michał Różyczka (Copernicus Astronomical Centre, Warsaw)

Old stellar clusters contain objects located above the turnoff point of the main sequence, which in their evolution seem to be "straggling" behind the remaining stars (they are "bluer" and seemingly younger). The talk is a review of observational properties of these object and theoretical problems they generate.


"Pulsar Wind Nebula G21.5-0.9 seen in the infrared"

Anna Zajczyk (Copernicus Astronomical Centre, Toruń)

The young PWN G21.5-0.9, heavily obscured in the optical due to its position in the inner Galaxy, reveals its beauty and complexity in the infrared. Images taken with ISAAC - VLT in the 1.64 micron [FeII] line show diffuse emission within the PWN which presumably originates from shocked ejecta. Spitzer, AOB-KIRĆFHT and polarimetric imaging, on the other hand, reveals a compact, strongly polarised nebula coincident with the X-ray core observed by Chandra. The measurements of the polarisation angle yields unique information on the magnetic geometry near the pulsar wind termination shock. The case of PWN G21.5-0.9 points to the infrared band as a promising window for observing optically obscured PWNe.


"The long term evolution of a planetary system with energy dissipation"

Cezary Migaszewski (Centre for Astronomy, N. Copernicus University, Toruń)

The study of the evolution of a planetary system with short-period planets in the time-scales of gigayears requires taking into account the dissipation of mechanical energy both in the star and in the planets. I will discuss the mechanism of energy loss as well as its consequences on the long term dynamics of a system consisting of a Sun like star and a hot Jupiter.


"Satellite Mission Planck: Description, Scientific Goals, and Early Results"

Krzysztof Górski (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA and Warsaw University Observatory)

Since August 2009 Planck has been observing the sky at frequencies from 30 to 857 GHz, measuring its principal target - the cosmic microwave background, but also everything else in the universe that radiates at these frequencies. I will describe the design and scientific goals of the mission, and the first scientific results from Planck, presented in Jan. 2011, covering a wide range of galactic and extragalactic astrophysics.


"The radio-X-ray correlation in black-hole binaries and the formation of jets"

Andrzej Zdziarski (Copernicus Astronomical Centre, Warsaw)

The radio flux in the hard state of black hole binaries is strongly correlated with the X-ray flux. The character of this correlation is found to strongly depend on the X-ray energy, as well as the correlation is found to extend to the soft spectral state, using data from Cyg X-1. The results imply that the jet is formed by the relativistic electrons of the Comptonization corona/hot flow, and rule out models in which the observed X-rays are emitted by the jet.


"GHz-Peaked-Spectrum Galaxies as sources of high energy emission"

Rafał Moderski (Copernicus Astronomical Centre, Warsaw)

I will present a simple dynamical description of young and compact (less then one kpc) radio galaxies, consisting of relativistic jet propagation into a uniform gaseous medium in the central parts of an elliptical host. The model will allow to discuss the broad-band lobe emission with a strong and complex high-energy component. I will also present X-ray and gamma-ray observations to support the model.


"Is dark energy just a mathematical difficulty?"

Boud Roukema (Centre for Astronomy, N. Copernicus University, Toruń)

The Concordance Model of the Universe is a good phenomenological model, fitting an interlocking web of many different extragalactic observations. However, it is incomplete, not only because the curvature and topology of comoving space have not yet been determined, but also because the observational estimate of the dark energy parameter (Omega_Lambda = 0.7) has a systematic uncertainty of order unity. This is because the standard phenomenological approach is based on solutions of the Einstein field equations that assume that the Universe is perfectly homogeneous, while the real Universe is inhomogeneous: the planet Earth exists. Two approaches to a more accurate cosmological model will be briefly introduced: the Tolman-Lemaitre-Bondi models and the averaging approach.


"Ultra high energy cosmic ray particles"

Pieter Bierman (Max-Planck-Institute fur Radioastronomie, Bonn)

Particles near 10^20 eV are the most energetic particles known to us in the universe, also called ultra high energy cosmic rays. Events have been detected of an energy up to 3x10^20 eV, which is a macroscopic energy. Independently, new spectral components of cosmic ray electrons, positrons and all nuclei have been detected, all of which are flatter. The now abundant observations are readily and quantitatively interpreted with the action in magnetic s tellar winds. This then may also explain the Auger data as due to the action of the relativistic jet in the radio galaxy Cen A on the starburst region full of cosmic rays. A further test will be the match to the Kaskade-Grande data covering the energy range from 10^14 eV to 10^{19} eV. With this we have proposed a theory for the origin of cosmic rays (1993), and tested the quantitative predictions (2009-2011); many more tests will be possible soon with neutrino data.


"Pi of the Sky telescopes in Spain and Chile . Photometric analysis of the Pi of the Sky data"

Małgorzata Siudek (Centre for Theoretical Physics, Warsaw)

Pi of the Sky is a system of robotic telescopes designed for observations of short timescale astrophysical phenomena, like prompt optical GRB emission. The apparatus is designed to monitor a large fraction of the sky with 12m to 13m range and time resolution of the order of 1 to 10 seconds. In October 2010 the first unit of the new Pi of the Sky detector system was successfully installed in the INTA El Arenosillo Test Centre in Spain. We have also successfully moved our prototype detector from Las Campanas Observatory to San Pedro de Atacama Observatory in March 2011. Database containing stars measurements from period 2006-2009 taken by the Pi of the Sky detector located in Las Campanas Observatory in Chile contains more than 2 billions measurements of almost 17 millions of objects. All measurements are available on the Pi of the Sky web site through a dedicated interface which also allows to download the selected data.Accurate analysis of Pi of the Sky data is a real challenge because of a number of factors that can influence measurements. Reading the chip with the shutter opened, strong and varying sky background, passing planets or planetoids, clouds and hot pixels are among possible sources of errors in our measurements. In order to facilitate analysis of variable stars we have developed a system of dedicated filters to remove bad measurements or frames. The spectral sensitivity of the detector is taken into account by appropriate corrections based on the spectral type of reference stars. This process is illustrated by the analysis of the BG Ind system where we have been able to reduce the systematic uncertainty to about 0.013 magnitudo.


"Transiting Extrasolar Planets: Detection, Analysis, Results"

Geza Kovacs (Konkoly Observatory, Budapest)

We summarize the available methodology used to detect and analyze transiting planets. Special attention will be paid on the detection, including detrending from systematics. We also review current ground- and space-based photometric projects, focusing on HATNet. Finally, we highlight some exceptional results, primarily those related to multi-planetary systems.


"Energy dissipation in relativistic jets"

Krzysztof Nalewajko (Copernicus Astronomical Centre, Warsaw)

"The question of relevant energy dissipation processes is central to understanding the physics of relativistic jets in radio-loud active galaxies and gamma-ray bursts. The standard scenario involving internal shocks faces several difficulties. Alternative mechanisms include stationary reconfinement shocks, magnetic reconnection and current-driven plasma instabilities


"Observational evidence for AGN feedback at pc scale"

Feng Yuan (Shanghai Astronomical Observatory, Chinese Academy of Sciences)

In a hot accretion flow, the radiation from the innermost region of the flow propagates outward and heats the electrons at large radii via Compton scattering. When the radiation is strong enough, L > 0.02 L_Edd, the electrons will be heated to be above the virial temperature. In this case, the BH activity will oscillate. We show that this mechanism can explain the intermittent activity of some compact young radio sources.


"The First Supermassive Black Holes"

Mitch Begelman (JILA, Boulder, Colorado)

The supermassive black holes that populate galactic nuclei could have grown from an early population of stars, or via the direct collapse of much larger masses of gas. I will discuss recent investigations of the latter possibility, focusing on the physics that may have regulated early black hole formation and growth. Black hole formation by direct collapse implies the existence of hitherto undetected classes of objects; I will outline the prospects for detecting them.


"On the existence of stellar mass binary black holes"

Tomasz Bulik (OAUW, Warsaw)

I will describe the ups and downs of looking for binary black holes. I will discuss the constraints on their abundance and formation rate in the local Universe.


"Studies of methanol maser sources in high-mass star-forming regions - discoveries based on Torun blind survey"

Anna Bartkiewicz (Astronomy Centre, UMK)

I will summary our studies of methanol maser sources that were discovered using Torun 32-m dish (Szymczak et al. 2000, 2002). We imaged selected 31 sources using the European VLBI Network and discovered a new class of objects - the ring-like structures. Next, we carried out four projects using radio interferometers VLA and VLBA as well as telescopes GEMINI in order to investigate where the exciting stellar sources lie with respect to the masers and to know the nature of massive young stellar objects.


"New and comprehensive ways to constraining the co-evolution of Black Holes and Galaxies"

Francesco Shankar (Max Planck Institute for Astrophysics in Garching)

Supermassive black holes (SMBHs) seem to be ubiquitous at the center of all galaxies which have been observed with high enough sensitivity with HST. SMBH masses are tightly linked with the masses and velocity dispersions of their host galaxies. Also, SMBHs are considered to be the central engines of active galactic nuclei (AGN). It is however still unclear how SMBHs have grown and if they have co-evolved with their hosts. In my talk I will derive, in ways independent of specific models, constraints on how SMBHs must have evolved within their dark matter halos. I will describe the accretion history of SMBHs from z~6 to z~0 by interconnecting a variety of data sets, including the AGN luminosity function, their clustering properties, and Eddington ratio distributions. I'll show results obtained through a novel numerical code which evolves the SMBH mass function and clustering adopting broad distributions of Eddington ratios. I will finally insert SMBH evolution in a wider cosmological framework for galaxy evolution directly constrained by the Sloan Digital Sky Survey.


"Solar like oscillations in Delta Scuti stars"

Victoria Antoci

Asteroseismology allows to access the most hidden part of the universe - the interior of stars. The outer convection zone in the Sun, for example, is known to generate acoustic noise in a broad frequency range, leading stochastically excited pulsation. From ground-based observations but also from space missions such as CoRoT and Kepler it is known that many solar-type stars show the same type of oscillations. As stellar mass and effective temperature increase the convective outer layer decreases. The transition zone from deep and effective to shallow convective outer zone takes place in the classical instability strip where the delta Scuti stars are located. These stars exhibit pulsations driven by an opacity mechanism acting like a heat engine. Theoretical models predicted solar-like oscillations to be still present in the very cool delta Scuti stars, but were never observed so far. Here we present the first evidence of stochastically excited oscillations in such a star, provided by NASA's Kepler satellite. Surprisingly, the measured effective temperature is higher than models predict, making this star a unique astrophysical laboratory to test our models on convection. Furthermore divers regions of the star can be sounded seismically as stochastically excited oscillations and pulsation driven by the opacity mechanism excite different radial overtones which penetrate into different depths of the star


"Ptaki w naszym otoczeniu"

Andrzej Kruszewicz (Warszawski Ogród Zoologiczny)


"20th Century Global Warming - Anthropogenic or Solar?"

Nir J. Shaviv (Racah Institute of Physics, Hebrew University of Jerusalem)

The 20th Century has seen a notable temperature rise, generally attributed to the greenhouse effect of anthropogenic gases, and a future "business as usual" policy is generally believed to be catastrophic. I will show, however, that the story is not that simple. I will address the following questions, all of which have a far from trivial and often surprising answer: How large is the greenhouse effect? Could some of the temperature rise be natural and not anthropogenic? If so, what is this natural driver? How sensitive really is Earth's climate? What should we expect in the future? How effective will the implementation of a cap and trade agreement be?


"Precision vs accurate cosmology - how well do we know our Universe?"

Krzysztof Bolejko (Astrophysics Department, University of Oxford)


"Is the enigma of the pulsar radio emission solved?"

Georgi Melikidze (Institut of Astronomy, Zielona Góra)

Various possible physical processes able to provide the observed pulsar radio emission will be discussed. The successful mechanism should be able to generate the waves capable of (a) escaping from the pulsar magnetosphere and (b) satisfying the observational constraints. The main attention will be paid to the coherent curvature radiation which seems to be the most appropriate mechanism from the observational point of view. Also, it is the only possible mechanism that can operate at the low altitudes, where the wave generation region is most likely located. The sequence of physical processes taking place in the pulsar magnetosphere that result in generation of the observed radio-emission will be presented.


"Origin, Structure, and Evolution of Hot Jupiters and Super-Earths"

Doug Lin (Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, China)

In the radial-velocity and transit searches, close-in planets are the first to be found. These planets are most likely formed at much larger distances from their host stars and migrated to their present-day location. I will discuss the implication of various recent discoveries including 1) the mass-period distribution of close-in planets, 2) their mass-radius relationship, 3) the mis-alignment of their orbital angular momentum vector and spin vector of their host stars, 4) their atmosphere 5) the dynamical architecture of closely-packed multi-planet systems, and 6) their presence around binary stars. I will discuss relevant and dominant physical processes which may have led to these features. Based on these theoretical consideration and population synthesis models, we suggest that 1) sequential core accretion is the dominant mode of planet formation process, 2) planets have considerable mobility, 3) habitable planets are common, and 4) dynamical evolution of planetary systems is an ongoing process.


"Formation of dwarf spheroidal galaxies in the Local Group"

Ewa Łokas (Copernicus Astronomical Center, Warsaw)

I will review two scenarios for the formation of dwarf spheroidal galaxies in the Local Group: the tidal stirring model and formation by mergers. In both cases the progenitors are disky dwarfs embedded in dark matter halos. Both scenarios produce objects with observational features remarkably similar to the classical dSph satellites of the Milky Way.


"On the 'Unaussprechlichen Kulten'"

H. P. Lovecraft (Miskatonic University, Arkham)

That is not dead which can eternal lie. And with strange aeons even death may die... Also, Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus pulvinar gravida metus at iaculis. Donec malesuada, nisl eu ultrices bibendum, ante metus consequat risus, nec porttitor purus nisl eu libero. Ut libero tortor, pretium nec sagittis ut, pretium nec est. Phasellus volutpat tempor enim ornare fermentum. Nam et lacus lectus, in ultrices augue. Proin nunc augue, scelerisque at pharetra at, gravida nec diam. Phasellus metus nibh, gravida in scelerisque dignissim, vulputate et ipsum. Cras leo nisi, placerat venenatis laoreet ac, aliquam eget ipsum. Nulla facilisi. Phasellus adipiscing tempus neque, vel semper dolor tempus eget. Aliquam porttitor rhoncus ipsum et luctus. Nullam suscipit pellentesque lectus vitae ultrices. Aliquam rutrum lacus justo, sed bibendum diam. Etiam ut lacinia nulla. Sed sapien nibh, pretium at pretium at, pretium et elit. Etiam venenatis tortor ac turpis scelerisque imperdiet.


"subject to ba announced"

Paweł Haensel (Copernicus Astronomical Center, Warsaw)


"Seismology of Beta Cephei stars, from the ground and from space"

Gerald Handler (Copernicus Astronomical Center, Warsaw)


"To be announced"

Szymon Gładysz (Technion, Haifa)


"Strong gravitational lenses as standard rulers in cosmology"

Marek Biesiada (Department of Physics, Silesian University, Katowice)

The accelerating expansion of the Universe is a great challenge for both physics and cosmology. Its discovery was possible because of the advances in the extragalactic distance measurements. While standard candles most notably Type Ia supernovae kicked off the issue, it is clear that statistical standard rulers like the Baryon Acoustic Oscillations are playing an increasingly important role. I will show that strongly gravitationally lensed systems with known central velocity dispersion of the lens, are good candidates for a new class of individual standard rulers - Einstein radius being standardized by stellar kinematics. This approach, pursued recently by us, is becoming attractive in light of ongoing lens surveys like SLACS based on different protocols than older searches.


"Measurements of neutrino velocity - past, present and future"

Katarzyna Grzelak (Institute of Experimental Physics, Warsaw University)

The OPERA experiment has recently presented the result on the measurement of neutrino velocity. Neutrinos from CERN were measured to arrive at the Gran Sasso Laboratory about 60ns earlier than expected assuming they travel with the speed of light. The details of the OPERA analysis and the recent updates will be presented together with the description of previous measurements of neutrino velocity and plans for the verification of the OPERA result.


"What was the last Nobel Prize in Physics given for?"

Stanisław Bajtlik (NCAC, Warsaw)