Wednesday Colloquium


"Eclipsing binaries as a unique tool for measuring the Hubble Constant with a precision of 1 %"

Grzegorz Pietrzyński (Astronomical Observatory, Warsaw University)


"Cosmology with the largest all-sky surveys: 2MPZ, WISE and beyond"

Maciej Bilicki (Department of Astronomy, University of Cape Town and Kepler Institute of Astronomy, University of Zielona Góra)

Our view of the low-redshift Cosmic Web has been revolutionized by various wide-angle galaxy redshift surveys such as the Sloan Digital Sky Survey. However, the trade-off between depth and sky coverage limits a systematic three-dimensional account of the entire sky beyond the Local Volume. In order to reliably map the Universe to cosmologically significant depths over the whole sky, one must draw on multiwavelength datasets and state-of-the-art photometric redshift techniques. I have been leading a dedicated programme of employing the largest photometric all-sky surveys – 2MASS, WISE and SuperCOSMOS – to obtain accurate redshift estimates of millions of galaxies. The first outcome of these efforts – the 2MASS Photometric Redshift catalogue (2MPZ) – was publicly released in 2013 and includes almost 1 million galaxies with a median depth over 300 Mpc. In this talk I will detail how this catalogue was constructed and how using the WISE mid-infrared survey together with SuperCOSMOS optical data allows us to push to depths over 1 Gpc on unprecedented angular scales. These photometric redshift samples, with about 20 million sources in total, provide access to volumes large enough to verify observationally the Copernican Principle of universal homogeneity and isotropy, as well as to study various properties of dark energy and dark matter through cross-correlations with other data such as the cosmic microwave or gamma-ray background.


"Stellar Populations and Kinematics of the Fornax dSph Galaxy"

Andrés del Pino (NCAC, Warsaw)

We present a comprehensive and detailed study of the stellar populations of the Fornax dwarf spheroidal galaxy. We will show its detailed star formation history (SFH), together with the spatial distribution and the chemo-dynamics of its stellar populations. This work is based on the deepest ground based Color-Magnitude Diagrams up to date, obtained from FORS1@VLT photometry (I~25); wide field photometry (~2 square degrees, V ~ 24), and spectroscopy of more than 2500 stars. Our results show that Fornax is a complex system. It has a long standing star formation from ~12 Gyr ago to ~0.5 Gyr or even more recent. Young populations concentrate in the central region of the galaxy, where the most intense star formation burst occurred ~8 Gyr ago. This was delayed ~2 Gyr with respect to the main peak of star formation. The spatial distribution of the stellar populations is irregular and only in the case of older stars it follows an elliptical distribution. We confirm the detection of shell-like structures and clumps of stars not aligned with the optical major-axis of the system stars younger than 3 Gyr. The later strongly suggest accretion of material with different angular momentum. We also detect a non negligible rotation signal (~12 kms -1) about the main optical axes of the galaxy as an important change in the preferred rotation direction of the galaxy at 8 Gyr (z~1). These results lead us to propose an scenario in which Fornax had suffered a major merger at z~1.


"Jet launching and hadronic processes in blazars"

Andrzej Zdziarski (NCAC, Warsaw)

The first part will be devoted to testing the model of jet launching utilizing the energy of black-hole rotation from magnetically arrested discs. This can be done by measuring magnetic fields in jets, in particular using the radio core shift, which is a dependence of the position of a radio core on frequency. A new variant of this method is presented. Application of it to luminous blazars implies that the jet opening angles are much smaller than the canonical value of 1/Gamma_jet. This then implies that the magnetization parameter is <<1, requiring the existence of an efficient mechanism of the magnetic-to-kinetic energy conversion. The second part will be devoted to a study of consequences of the blazar model with emission dominated by hadronic processes, recently quite popular, to models of accretion. It is shown that the power of jets in this model is both highly super-Eddington and exceeding the accretion luminosity by a factor of thousands. This is shown to be inconsistent with standard accretion models, which presents a strong argument against the hadronic model.


"Spatially resolved observations of planetary nebulae by Herschel Space Observatory"

Ryszard Szczerba (NCAC, Toruń)

Herschel PLanetary Nebulae Survey (HerPLaNS) was a photometric and spectroscopic survey of Planetary Nebulae (PNe) in the far-IR using the Herschel Space Observatory. It was one of the largest open time programes with about 200 hours of observations allocated. The project is part of a bigger project, which aims at collecting multi-wavelength observations from the X-ray to the millimetre wavelengths to fully charecterse the energetic system of PNe. In my talk I will present results we have obtained up to now using the collected data.


"Nonthermal emission from supernova remnants"

Oleh Petruk (Institute for Applied Problems in Mechanics and Mathematics, Lviv National University, Ukraine)

Supernova remnants (SNRs) are the main objects to study acceleration of galactic cosmic rays. Magnetic field in the Galaxy deflects relativistic particles on their way toward the observer. Therefore, information about high-energy processes in SNRs may be inferred only from their nonthermal emission. We review the present status of observations and modeling of the cosmic-ray radiation in SNRs, in radio, X-ray and gamma-ray bands.





Łukasz Wyrzykowski (Astronomical Observatory, Warsaw University)


"Physics after the discovery of the Higgs particle"

Jan Kalinowski (Institute for Theoretical Physics, Warsaw University)


"Variable stars related to the X-ray sources"

Marcin Kiraga (Astronomical Observatory, Warsaw University)

Photometric data from the ASAS survey are used for the search for variable stars related to ROSAT X-ray sources. There are more than 3600 stars found so far. The main variability types are rotationally variable stars due to presence of spots and eclipsing binaries. Most of them have X-ray emission of coronal origin, there are a few cataclysmic binaries and early type binaries with colliding winds. We present some interesting variable stars and rotation period - X-ray activity relation for magnetically active stars.


"Through the eye of SAURON: evolution of dwarf elliptical galaxies in the Virgo cluster"

Agnieszka Ryś (ESO, Garching)

Dwarf elliptical galaxies (dEs) are the most common galaxy class in dense environments, outnumbering all other classes combined. Their low masses make them ideal test beds for studying different mechanisms that shape galaxies, since both external influences and internal feedback mechanisms are far more extreme in dwarfs than in massive galaxies. dEs are a surprisingly inhomogeneous class, which has made it difficult to relate different dE subtypes to each other, as well as to place the whole class in the larger context of galaxy assembly and (trans)formation processes. Here I will present the kinematic, dynamical and stellar population analysis of a sample of 12 dEs observed using the SAURON integral-field unit mounted on the 4.2m William Herschel Telescope (ORM, La Palma). We have obtained large-scale two-dimensional maps of kinematic and stellar population properties for objects for which (with very few and small-scale exceptions) only one-dimensional profiles were available before. From the variety of dE properties we find and confirm with our data, and through their analysis, we are able to show tidal harassment signatures in the galaxies' dynamical and stellar population properties, paying particular attention to radial trends within the cluster. We can thus establish dE progenitor class with more accuracy and define the place of dEs among other galaxy types.


"Probing the nature of Dark Matter and Dark Energy: from the Local Group to the Local Universe"

Wojciech Hellwing (Durham University)

Cosmology asks fundamental questions about the structure and composition of the Universe, its birth, evolution and future fate. The current understanding is encapsulated in a well established concordance cosmological model, the LCDM (Lambda Cold Dark Matter) model, whose parameters have been measured to remarkable precision. Nonetheless, the current cosmogony is characterized by several fundamental puzzles about the physical nature of the Universe. The most important questions concern the nature of the two components that dominate the evolution and fate of the Cosmos: Dark Matter (DM) and Dark Energy (DE). In my talk I will discuss my research focusing on possible ways of extracting the information about the physical nature of the DM and DE components using observations of the Local Universe (LU). Our cosmic neighbourhood stretches from the “backyard” dwarf galaxies of the Local Group (LG) to the relatively nearby galaxies woven into the Cosmic Web extending up to hundreds of Megaparesecs around us. The main topic of my talk will be twofold: (i) how we can explore the information encoded in the peculiar motions of local galaxies to study the nature of the DE and gravity; (ii) and how we can use the connection between the larger-scales and the local neighbourhood to get insights into the physical nature of DM and LCDM specific characteristics of galaxy formation.


"Simulations of Optically Thick Accretion onto Black Holes - The Power of Radiative Jets"

Aleksander Sądowski (MIT Kavli Institute for Astrophysics and Space Research)

In this talk I will describe challenges of simulating thin and super-critical accretion disks and present the numerical methods that allow for global simulations in general relativity. I will then present in detail solutions for disks accreting above the Eddington rate and show that the radiative jets they produce can be very powerful even without any extraction of the black hole rotational energy.


"Changes in CAMK Network"

Krzysztof Leszczyński (NCAC, Warsaw)

From time to time we need to make major changes in our network. This time we need to change the type of authentication. Login and password will no longer be enough to log into our network from the remote sites. Some of services like email will change too. Keywords: eduroam, IPv6, tunnels, VPN, email, ssh.


"Recent results from the hard X-ray - sensitive satellite NuSTAR"

Grzegorz Madejski (Stanford University)



CLOUDY Workshop



"Searching for Y dwarfs at the faint limits of WISE"

Mariusz Gromadzki (Universidad de Valparaíso, Chile)

WISE mission, which was designed to detect the coolest objects, has lead to a breakthrough in the brown dwarfs research. It has found plenty of late T dwarfs and identified first Y dwarfs. We have explored the WISE All-Sky database applying various selection criteria to obtain sample of W2-only detected and low signal-to-noise (S/N≥8) late T and Y dwarf candidates. Spurious sources were removed using database selection criteria defined through analysis of a control sample comprising isolated point-like non-variable non-moving sources from the SDSS. We perform J-band photometric follow-up on 4-8m class telescopes to prove the high proper motion and low temperature of these objects. The low resolution near-IR spectroscopy of the best candidates has confirmed a few late T dwarfs (>T8) and one Y dwarf. Here we will present summary of ground based photometric and spectroscopic follow-up of the candidates.


"Can Novae Make Supernovae? Surprising Connections between Erupting Stars"

Michael Shara (American Museum of Natural History)

Classical novae and supernovae were long thought to be completely separate astrophysical phenomena. This is no longer true; at least some supernovae may have symbiotic nova precursors. I?ll review the current state of knowledge of the temporal evolution of the white dwarfs in novae, and the Tree of Death of Supernovae. These will help illuminate the still-controversial but ultimately testable, hypothesized connection between novae and supernovae.


"Chemical abundances of giants in the S-type symbiotic systems. Clues for the enrichment with Titanium and Zirconium"

Cezary Gałan (NCAC, Warsaw)

The elemental abundances of symbiotic giants are essential to address the role of chemical composition in the evolution of symbiotic binaries, to map their parent population, and to trace their mass transfer history. However, the number of symbiotic giants with fairly well determined photospheric composition is still insufficient for statistical considerations. Until quite recently photospheric chemical compositions were known for few only cases of red giants in the S-type symbiotic systems. In the recent studies we have increased this number by several times, up to nearly 30 giants, making it possible to perform a first attempt of statistical analysis. Our chemical composition measurements were performed with use of high-resolution (R ∼ 50 000), high signalto- noise (S/N), near-IR spectra. Spectrum synthesis analysis employing standard local thermal equilibrium (LTE) and atmosphere models was used to obtain photospheric abundances of CNO and elements around the iron peak (Sc, Ti, Fe, and Ni). Our analysis revealed metallicities distributed in a wide range: from significantly sub-solar to slightly super-solar in several cases, with the largest representation around solar and slightly sub-solar metallicity. The enrichment in 14N isotope found in all these objects, indicates that the giants have experienced the first dredge-up, what is confirmed also by the low 12C/13C ratio, always whenever its measurement was possible. We found that the relative abundance [Ti/Fe] is large in both, the red and the yellow symbiotic systems, what suggests it can be an intrinsic characteristic of all symbiotic giants. It will also be discussed on the s-process enhancement observed in some of these objects, manifesting mainly by Zirconium enrichment, what possibly may be the case of roughly a half of our sample of giants in the S-type symbiotic systems.


"Quasars and dark energy"

Bożena Czerny (Center for Theoretical Physics and CAMK, Warsaw)

Dark energy can be studied with a number of probes, broadly classified as standard candles and standard rulers. The use of several independent probes is needed to get accurate and reliable results since every probe has its particular systematic problems/biases. Quasars do not seem to be obvious standard candles but there are two ways to pursue. The first method is based on the selection of special sub-class of quasars, which radiate precisely at Eddington ratio. The second method can use all quasars, but requires to perform the monitoring of the quasar variability of the continuum and of the emission lines. Reverberation studies (i.e. the measurements of the time delay of the line emission with respect to the continuum) allow to establish the absolute monochromatic luminosity of a given source independently of its redshift. We developed a theory which explains the delay-luminosity relation known for nearby sources and allows to extrapolate this type of relation towards higher black hole mass sources, like quasars at redshifts of a few. Preliminary studies are being done using our data from the dedicated campaign with the 11-m SALT telescope. These high-quality data allow to study the spectra in much detail (including the spectra decomposition into lines and Fe II pseudo-continuum) in order to determine the possible systematic errors. Later the method will be applied to expected spectroscopic surveys; in addition, current estimates indicate that the project can also be undertaken with a photometric survey of the quality of LSST. The advantage of using quasars lies in their broad range of redshifts, large number of available sources and weak evolution of their metallicity with redshift.


"High-resolution radio view of the AGN jets and their magnetic fields"

Tuomas Savolainen (Aalto University Metsähovi Radio Observatory, Kylmälä )

Understanding the mechanisms for launching, accelerating, and collimating the magnetized jets of plasma from accreting black holes is one of the central questions in relativistic astrophysics. During the past decade significant progress has been made in the theoretical description of the jet formation, and especially in the field of complex general relativistic magnetohydrodynamic simulations. High-resolution radio imaging of (sub-)parsec-scale structures in the jets, especially in polarization, is one of the very few ways to derive observational constraints for the physical conditions in the jets in or close to their acceleration and collimation site, and thus place constraints on the theory. In this talk I will discuss recent results from the state-of-the-art very long baseline interferometry observations regarding the jet magnetic field structure, acceleration/collimation of the flow, and the conditions near the black hole itself.


"The Polish doughnut revisited"

Marek Abramowicz (NCAC, Warsaw)


"Arachne’s fate. On textile production in Bronze Age Greece and craft research in academia"

Agata Ulanowska (The Institute of Archaeology, Department of History, Warsaw University)


"Grand challenge: Computational Neurophenomics for understanding people’s behavior"

Włodzisław Duch (Department of Informatics, Nicolaus Copernicus University, Toruń)

The astronomical complexity of the brain is unmatched in the known universe. The engineering approach to understanding is by creating artificial brains. Progress in this direction is briefly reviewed. All mental states result from neural dynamics of the brain. Understanding mental processes in a conceptual way, without understanding their underlying neurodynamics, will always be limited. Phenomics tries to describe phenotypes at all levels, from genetic to behavioral. A brief review of factors that influence brain development and facilitate building perceptual and cognitive skills, representation of concepts in the brain, will be presented. Neuroimaging allows for reading intentions and control of brain processes. Natural sciences got seriously engaged in research on consciousness, mind and inner world only with development of functional neuroimaging techniques showing brain processes during various tasks. As a result mental states are losing their private character. External observer can see and correctly interpret brain processes that have not yet become conscious or will never be conscious. Self, our personal identity, is one of many processes that brain is running. How are these processes implemented? Computational neuroscience is leading the way to show ho brain activity is linked to behavior.


"Galaxy clustering using photometric redshifts"

Andrzej Sołtan (NCAC, Warsaw)

We investigated the evolution of the galaxy two point correlation function (CF) over a wide redshift range, 0.2 < z < 3. For the first time the systematic analysis covers the redshifts above 1 - 1.5. The catalogue of ~250000 galaxies with i+ < 25 and known photometric redshifts in the Subaru Deep field is used. First, the 2D CF is determined for several distance bins. Calculations are based on the quantitative differences between the surface distributions of galaxy pairs with comparable and distinctly different photometric redshifts. The power law approximation for the CF is used. Then, the 3D functions for all the selected luminosities and distances are calculated. The power-law parameters of the CF, the slope and the correlation length, are determined. Both parameters do not show strong variations over the whole investigated redshift range. The slope of the luminous galaxies appears to be consistently steeper than that for the fainter ones. The linear bias factor, b(z), grows systematically with redshift; assuming the local normalization b(0) = 1.1-1.2, the bias reaches 3 - 3.5 at the high redshift limit.


"Hyperons in neutron stars"

Morgane Fortin (NCAC, Warsaw)

The existence two-solar-mass neutron stars (NSs) puts strong constraints on the properties of matter at high density and in particular questions the existence of hyperons (baryons containing at least one strange quark) in the core of massive NSs. I will present ongoing projects which examine the consequences of the presence of hyperons inside NSs on the macrophysical properties of NSs (radius, thermal evolution, ...) and on the nuclear properties of matter. Their consistency with astrophysical observations and nuclear experiments will be assessed.


"Accretion Disks, Elevated"

Mitch Begelman (JILA, Boulder, CO)

In addition to driving the turbulence that transfers angular momentum and permits accretion disks to accrete, the magnetorotational instability also creates a strong, highly organized magnetic field parallel to the disk plane. Although this field is buoyant and continuously escapes, under certain conditions it can build up to the point where it dominates other forms of pressure in supporting the disk vertically against gravity. I will discuss the properties of such "magnetically elevated" disks and show that their existence can resolve several longstanding problems in accretion disk theory.


"Blue stragglers in globular clusters"

Michał Różyczka (NCAC, Warsaw)

My talk is divided into three parts. The introduction comprises a bit of history, some basic information about blue stragglers (BSs), an outline of procedures employed to select BSs from among cluster members, and an outline of hypotheses proposed to explain their nature. The second part is devoted to correlations between cluster parameters and BSs distribution, and to links these correlations imply between the dynamical evolution of globular clusters and characteristics of BSs population. In the third part the CASE project is briefly introduced, and some of its results are presented (in particular – several detailed portraits of blue stragglers).


"Magnetic dissipation behind extreme high-energy phenomena"

Krzysztof Nalewajko (NCAC, Warsaw)

Gamma-ray astronomy provides us with several types of extreme phenomena characterized by high apparent luminosity and rapid incoherent variability: flares in blazars, radio galaxies, pulsar winds, gamma-ray bursts. It seems plausible that all these events could be produced in relativistic magnetized outflows. In such environments, the most natural dissipation mechanism is relativistic magnetic reconnection. Significant progress in understanding relativistic reconnection has been made in recent years, however, many open questions remain to be answered.


"TBARadio galaxy scaling relations, radio galaxy remnants, and the nature of radio loud quasars"

Leith Godfrey ( Netherlands Institute for Radio Astronomy )

The first part of this presentation will be devoted to a discussion of the scaling relation between jet power and extended radio luminosity in radio galaxies. In principle, this scaling relation can be a powerful tool in statistical studies of radio galaxies and their energetic impact on the surroundings, provided the relation can be adequately calibrated. However, previously reported scaling relations, including those based on X-ray cavity measurements, are dominated by the mutual distance dependence of jet power and radio luminosity. After accounting for the mutual distance dependence, we find a significantly flatter relation than previously reported, and this result has strong implications for studies of radio mode feedback and radio galaxy physics. In the second part of the presentation, I will discuss our recent work on the remnant phase of radio galaxy evolution, and some of the ways in which the remnant population may be used as an effective tool to constrain radio galaxy physics. In particular, I will describe a search for remnant radio lobes associated with optically active AGN. Such objects are expected to exist if under certain conditions radio loud quasars transition to a radio quiet state. An evolutionary connection between radio loud and radio quiet quasars is predicted within certain classes of model, and our approach provides a clear test of such models.


"Absorption measure distribution: models vs observations "

Agata Różańska (Copernicus Astronomical Center, Warsaw )

We present how modelled absorption measure distribution (AMD) computed form the warm absorber under pressure equilibrium can explain the observed one in Mrk 509. AMD is constructed from observations of narrow absorption lines in radio-quiet AGN with warm absorbers. We study the properties of the warm absorber in Mrk~509 using recently published broad-band spectral energy distribution observed with different instruments. This spectrum is an input in our radiative transfer computations with full photoionisation treatment using {\sc titan} code. We found theoretical AMD which matches the observed one determined on the basis of 600 ks RGS XMM-Newton spectrum of Mrk~509. Our model puts strong constraints that the density of the warm absorber should be high enough to produce strong opacity jumps which are responsible for observed AMD dips. The excelent spectral resolution of ATHENA instrument will provide more poins in the observed AMD of many AGN and will allow for better test of our model.


"A New Scenario for IMBH Formation in Globular Clusters - Observational Imprints"

Mirosław Giersz (NCAC, Warsaw)

I will discuss a new scenario for formation of intermediate mass black holes in globular clusters. In this scenario, intermediate mass black holes are formed as a result of dynamical interactions of hard binaries, containing a stellar mass black hole, with other stars and binaries. I will discuss the necessary conditions to initiate the process of intermediate mass black hole formation and the dependence of the rate of mass increase on the global cluster properties. I will also discuss possible observational imprints of IMBH presence in star clusters.


"More Than Meets the Eye: How do we contemplate contemporary art?"

Kathryn Zazenski (Fulbright Fellow and NCAC, Warsaw)

In 1917 the path of contemporary art was forever changed by Marcel Duchamp and his introduction of the "readymade." The readymade paved the way for art to function in the service of the mind as opposed to its prior service of being pleasing to the eye. In this talk I will discuss ways of contemplating contemporary art; the shifting role of beauty, material, and concept, illustrating these ideas with a range of works from international artists over the past 100 years


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

Joanna Zalipska (National Centre for Nuclear Research, Warsaw)