Abstracts of submitted talks & posters (IN ALPHABETICAL order)
Ixandra Achitouv – Swinburne University
Title: Improving reconstruction of the baryon acoustic peak : the effect of local environment
Abstract: Precise measurements of the baryon acoustic oscillation (BAO) scale in the clustering pattern is a central goal of current and future galaxy surveys. The BAO peak may be sharpened using the technique of density-field reconstruction, in which the bulk displacements of galaxies are estimated using a Zeldovitch approximation. We use numerical simulations to demonstrate how the accuracy of this approximation depends strongly on local environment, and how this information may be used to construct an improved BAO measurement through environmental re-weighting and using higher-order perturbation theory. We outline further applications of the displacement field for testing cosmological models.
type: talk slot: Tuesday, 12:20-12:35 participant absent
Raul Angulo – CEFCA, Teruel
Title: TBA
Abstract: TBA
type: talk slot: Tuesday, 16:00-16:45
Małgorzata Bankowicz – Astronomical Observatory of the Jagiellonian University
Title: Modelling LIRGs and ULIRGs – poster
Abstract: Using infrared (IR) (8μm − 10^3μm) data of dusty galaxies we analyze [Ultra]Luminous InfraRed Galaxies (LIRGs and ULIRGs). These galaxies have the highest star formation rate among other star forming galaxies. We use data from the AKARI Deep Field-South (ADF-S) enriched with the data from the Herschel satellite. We use the IR data to model Spectral Energy Distributions (SEDs) of these galaxies. We use cmcirsed model (Caitlin M. Casey InfraRed Spectral Energy Distribution) and the FUV-to-FIR models included in the CIGALE code(Code Investigating GALaxy Emission) version v0.5 to estimate dust mass and dust temperatures in [U]LIRGs. We concluded that [U]LIRGs have more dust than normal galaxies. I would like to present a poster and not to give a talk.
type: poster slot: Tuesday poster session 17:20-17:35
Francis Bernardeau – IAP Paris
Title: Large-deviation functions in the large-scale structure cosmology
Abstract: The existence of large deviation functions (LDF) is ubiquitous in many fields of applied mathematics and statistical mechanics such as basic random processes, equilibrium many body systems or even nonequilibrium, disordered and chaotic systems. I present here results that show that such large deviation functions can be built in the context of the evolution of the large-scale structure of the universe. The presentation will introduce the two key relations the LDF obey and give example on how such relations can be exploited in the context of perturbation theory calculations.
type: talk slot: Tuesday, 10:15-10:40
Marek Biesiada – University of Silesia
Title: Cosmology with strong lensing systems
Abstract: With continuing theoretical efforts and with new generation of lensing surveys (SLACS, BELLS, SL2S, CFHTLenS), strong gravitational lensing has developed into a serious technique in extragalactic astronomy (galactic structure studies) and in cosmology. In particular, strong lensing is becoming an important tool of modern cosmology used to address the issues of dark energy and dark matter in a way competitive to other probes. In my talk I will focus attention on galaxy-galaxy strong lensing combined with stellar dynamics and time delays. I will show recent results of cosmological parameters (like the Hubble constant and cosmic equation of state) estimated with such systems and briefly discuss the perspectives for the future.
type: talk slot: Monday, 15:05 – 15:30
Maciej Bilicki – University of Zielona Góra
Title: Cosmology with the largest all-sky galaxy surveys
Abstract: Wide-angle galaxy redshift surveys such as the SDSS have revolutionized our knowledge of the large-scale structure of the Universe. A trade-off between depth and sky coverage of such spectroscopic surveys limits however a systematic three-dimensional account of the entire sky beyond the Local Volume, while various aspects of cosmology require comprehensive all-sky mapping of the cosmic web to considerable depths. In order to probe the whole extragalactic sky beyond 100 Mpc, one must draw on multiwavelength datasets and state-of-the-art photometric redshift techniques. I will summarise our dedicated programme that employs 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. I will detail how this catalogue was constructed and how it is being used for various cosmological tests. I will also present how combining the WISE mid-infrared survey with SuperCOSMOS optical data allowed 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 study observationally the Copernican Principle of universal homogeneity and isotropy, as well as to probe various aspects of dark energy and dark matter through cross-correlations with other data such as the cosmic microwave or gamma-ray backgrounds. Last but not least, they constitute a test-bed for forthcoming wide-angle multi-million galaxy samples expected from such instruments as the SKA, Euclid or LSST.
type: talk slot: Friday, 14:05-14:30
Krzysztof Bolejko – University of Sydney
Title: Local cosmological environment and its impact on observations
Abstract: The Universe on scales 10-100 Mpc consists of structures such as voids, galaxy clusters, filaments and superclusters. These various structures participate differently in the global expansion of the Universe. On one side of the spectrum we have clusters of galaxies, which are virialized and do not expand at all. On the other side we have cosmic voids, which expand at a much faster rate than the average rate of the expansion of the Universe. In this talk I will examine how cosmic structures within 100 Mpc affect the Hubble flow and CMB anisotropies. I will present models, which suggest that part of the anisotropies of the CMB and Hubble flow, in particular the dipole and quadrupole, might be of non-kinematic origin, and is induced via relativistic non-linear effects by cosmic structures within 100 Mpc.
type: talk slot: Tuesday, 11:50-12:15
Sownak Bose – ICC Durham University
Title: Cosmology with Sterile Neutrinos
Abstract: The claimed detection of the (as yet) unidentified 3.53 keV X-ray line has prompted a surge of interest in models beyond CDM, with one of its most promising candidates coming in the form of the sterile neutrino, which is well-motivated by particle physics extensions to the Standard Model. Given the vast parameter space that can be explored, and the discernible difference in structure formation relative to CDM, it is an exciting venture to see if viable candidates can be constrained using observations of the local universe in conjunction with the most recent results from Planck. In this talk, I will demonstrate how we can use semi-analytic models to predict properties of galaxies in sterile neutrino cosmologies, and how these can be used to narrow down candidates of interest using a combination of Milky Way satellite counts and the reionisation of the universe.
type: talk slot: Wednesday, 14:30-14:45
Fracois Bouchet – IAP Paris
Title: Planck 2015 CMB cosmology.
Abstract: TBA
type: talk slot: Tuesday, 09:30-10:10
Richard Bower – ICC Durham University
Title: The EAGLE simulation
Abstract: TBA
type: talk slot: Monday, 10:00-10:30
Enzo Branchini – Roma Tre
Title: The Large Scale Structure Path to Dark Matter Detection
Abstract: The presence of dark matter [DM] in the Universe has been firmly established from the observations of its gravitational effects on ordinary matter, and in particular from the properties and evolution of the Large Scale Structure [LSS]. However, the fundamental nature of this component is still unknown, Fortunately, DM is expected to exhibit non-gravitational interactions, being able to induce electromagnetic radiation associated to cosmic structures. In this talk I will show that the LSS can be used to efficiently extract the DM signal by cross-correlating barionic tracers (catalogues of extragalactic objects) with the gamma-ray sky (observed by the Fermi-LAT telescope). For the first time we have detected significant correlation signal that, intriguingly, can be accounted for by postulating a DM component composed of weakly interacting particles. Future data collection and dedicated analyses will help in distinguishing this possibility from other astrophysical interpretations of the signal.
type: talk slot: Tuesday, 15:05-15:30
Marius Cautun – ICC Durham University
Title: Optimized void stacking using shape information
Abstract: I will introduce a new method for stacking voids and computing their profile that greatly increases the potential of using voids as a tool for precision cosmology. Since voids are very non-spherical and have most of their mass at their edge, they should be described with respect to their boundary and not with respect to some poorly-chosen void centre, as in the conventional spherical stacking approach. The boundary stacking/profile is obtained by computing the distance of each volume element from the void boundary. Following this, voids are stacked and their profiles are computed as a function of this boundary distance. This new approach increases the weak lensing signal of voids, both shear and convergence, by a factor of two when compared to the spherical stacking of voids. It also leads to steeper void density profiles that are characterised by a very slow rise inside the void and a pronounced density ridge at the void boundary, which is in agreement with theoretical models of expanding spherical underdensities. The resulting boundary density profile is self-similar when rescaled by the thickness of the density ridge, meaning that the average rescaled profile is independent of void size. The boundary velocity profile is characterized by outflowing mass in the inner regions, the amplitude of which scales with the void size, and by a strong inflow into the filaments and walls delimiting the void.
type: talk slot: Thursday, 11:20-11:45
Michał Chodorowski – CAMK
Title: A novel model of redshift distortions
Abstract: In deep three-dimensional surveys of galaxies, as the third coordinate of a galaxy’s position in space its redshift is adopted. Density inhomogeneities in the Universe induce deviations from the simple Hubble velocity flow of galaxies. As a result, redshift is not a perfect estimator of the true distance and maps of the galaxy distribution in REDSHIFT SPACE give a distorted view of their spatial distribution in real (configuration) space. In particular, the two-point (auto-)correlation function of galaxies is anisotropic in redshift space. Interestingly, the amount of anisotropy depends on the rate of growth of density fluctuations in the Universe, which is different in dark energy and modified gravity cosmologies. A measurement of the growth rate from galaxy redshift surveys can thus serve as a method to differentiate between various competing cosmological theories, explaining the current acceleration of the Universe expansion in a qualitatively distinct way. To achieve this goal, very accurate estimates of the growth rate from observations, as well as precise theoretical models of the correlation function of galaxies in redshift space are needed. The accuracy of the measurements steadily increases with time. However, despite of numerous attempts over the last two decades, there is still no model which satisfactorily predicts isocontours of the correlation function in redshift space. After describing a few most popular models existing in the literature, I will briefly present my recent work on the subject. My model has more realistic physical assumptions and in consequence fares much better than the former when compared to the results of N-body simulations.
type: talk slot: Friday, 10:35-11:00
Bożena Czerny – Center for Theoretical Physics, PAS
Title: Quasars for Cosmology
Abstract: Quasars are the brightest persistent sources in the Universe. Only a fraction of galaxies pass through this very special stage of the evolution. Nevertheless, quasars are now widely recognized as being important in cosmology. Their well established active role is to provide the requested feedback for the galaxy evolution. Their passive application also started long time ago, they were used to probe the intergalactic medium and to measure the Hubble constant. Now their passive role expands, as quasars can provide alternative method to measure the expansion of the Universe and to determine the properties of the dark energy. I will concentrate in my review on various specific methods proposed for this most recent goal.
type: talk slot: Monday, 14:00-14:30
Marek Demiański – University of Warsaw
Title: TBA
Abstract: TBA
type: talk slot: Friday, 09:30-10:00
Anna Durkalec – National Centre for Nuclear Research
Title: Properties and evolution of galaxy clustering at 2 < z < 5 based on the VIMOS Ultra Deep Survey.
Abstract: Our work focuses on the study of the properties and evolution of galaxy clustering for galaxies in the redshift range 2.0<z<5.0 from the VIMOS Ultra Deep Survey (VUDS), which is the largest spectroscopic galaxy survey at z>2. We measure the spatial distribution of a general galaxy population at redshift z∼3 for the first time with a high accuracy using a general population of 3022 galaxies with robust spectroscopic redshifts covering in total 0.8 deg^2. We extended the clustering measurements to the luminosity and stellar mass-selected sub-samples in order to study the dependence of galaxy clustering on these two physical parameters. Our results show that the clustering strength of the general galaxy population does not change significantly from redshift z∼3.5 to z∼2.5, but in both redshift ranges strongly depends on luminosity and stellar mass, with more luminous and more massive galaxies being more clustered than less luminous (massive) ones. Using the halo occupation distribution (HOD) formalism we measured an average host halo mass at redshift z∼3 significantly lower than the observed average halo masses at low redshift. Additionally, in agreement with the current scenario of the hierarchical formation of the large-scale structure, within our sample we observed an increase of the average host halo masses from z∼3.5 to z∼2.5. We concluded that the observed star-forming population of galaxies at z∼3 might have evolved into the massive and bright (Mr<−21.5) galaxy population at redshift z=0. Finally, we study the efficiency of star formation and stellar mass assembly. We find that the integrated star formation efficiency is quite high at ∼16% for the average galaxies at z∼3.
type: talk slot: Friday, 15:40 – 15:55
Martin Feix – IAP Paris
Title: The cosmic growth rate from an alternative observational test
Abstract: Spatial variations in the distribution of galaxy luminosities, estimated from redshifts as distance proxies, are correlated with the peculiar velocity field. Comparing these variations with the peculiar velocities inferred from galaxy redshift surveys is a powerful test of gravity and dark energy theories on cosmological scales. Using galaxy data from the SDSS DR7, we perform this test and estimate the growth rate of density perturbations at z ~ 0.1. This unique measurement is complementary to those obtained with more traditional methods (including clustering analysis), and its accuracy is competitive with other methods when applied to similar datasets.
type: talk slot: Tuesday, 16:50-17:15
Carlos S. Frenk – ICC Durham University
Title: The CDM riddles
Abstract: TBA
type: talk slot: Wednesday, 10:30-11:10
Ben Granett – INAF Brera Observatory
Title: The Integrated Sachs-Wolfe Signal from BOSS Super-Structures
Abstract: Cosmic structures leave an imprint on the microwave background radiation through the integrated Sachs-Wolfe effect. We construct a template map of the signal using the SDSS-III Baryon Acoustic Oscillation Survey at redshift 0.43 < z < 0.65. We verify at the 97% confidence level the imprint of this map on the CMB using Planck data and show consistency with the density-temperature cross-correlation measurement. Using this ISW reconstruction we investigate the presence of ISW sources and examine the properties of the Granett et al (2008) supervoid and supercluster catalogue. We characterise the three-dimensional density profiles of these structures for the first time, shedding new light on the original measurement.
type: talk slot: Friday, 10:05-10:30
Mikołaj Grzędzielski – Center for Theoretical Physics, PAS
Title: Searching for deterministic chaos in the accreting black holes
Abstract: Hardly any of the observed black hole accretion disks in X-Ray binaries and active galaxies shows constant flux. When the local stochastic variations of the disk occur at specific regions where a resonant behaviour takes place, there appear the Quasi-Periodic Oscillations (QPOs). If the global structure of the flow and its non-linear hydrodanamics affects the fluctuations, the variability is chaotic in the sense of deterministic chaos. Our aim is to solve a problem of the stochastic versus deterministic nature of the black hole binaries variability. We use both observational and analytic methods. We use the recurrence analysis and we study the occurrence of long diagonal lines in the recurrence plot of observed data series and compare it to the surrogate series. We analyze the data of six X-Ray binaries – GRS 1915+105, IGR J17091-3624, GRO 1655-40, XTE J1650-500, XTE J1500-564 and GX 339-4 observed by Rossi X-ray Timing Explorer. In these sources, the non-linear variability is expected because of the global conditions (such as the mean accretion rate) leading to the possible instability of an accretion disk. The thermal-viscous instability and fluctuations around the fixed-point solution occurs at high accretion rate, when the radiation pressure gives dominant contribution to the stress tensor.
type: poster slot: Tuesday poster session 17:20-17:35
Wojciech Hellwing – ICC Durham University
Title: Copernicus Complexio: testing the CDM paradigm from the Local Group to the Local Universe
Abstract: I am going to present new results stemming from the Copernicus Complexio (COCO) suite of high-resolution zoom-in cosmological simulations.
type: talk slot: Wedensday, 10:00-10:25
Wojciech Hury, Aleksander Nowiński – ICM Warsaw University
Title: COCOS – a database for COCO simulation results
Abstract: Large scale cosmological simulations since many years provide very interesting data shared among scientist in the world. This led to creation of a Millennium and Bolshoi databases which offer community access to the large datasets produced in previous simulations. A new database is being developed to offer hosting for results of the COCO computational experiment conducted in ICM supercomputing centre. The database will be built for two main results of the COCO simulation runs, each having approx 70 TB of raw data, as a result of simulation of 10^10 particles, with 160 snapshots in time. Within this data objects are identified and stored in SQL database which may be queried by users. Primary goal of building COCOS database is to provide users with advanced interface which will allow users to query both objects and raw data. Objects will be stored in relational database, and raw data will be accessible for further analysis. Database will allow not only to download the files but also to connect directly to the API with astronomy specific tools compatible with IVOA API, and with custom REST API as well. The database is a part of the large effort, a project OCEAN, which goal is to build a modern scientific data infrastructure and data repositories in Poland.
type: talk slot: Wednesday, 16:10-16:25
Agnieszka Janiuk – Center for Theoretical Physics, PAS
Title: Activity of supermassive black holes
Abstract: On the cosmological scale, evolution of the Universe is much affected by the presence of supermassive black holes. One of the interesting issues is the intermittent character of their activity in the host galaxies, and the so-called duty cycles. On the other hand, a large fraction of SMBHs must have passed through the phase of a merger. In this context, the effects of BH spin reorientation as well as the signatures of gravitational recoil effect have been observed in a number of distant quasars. Thus the understanding of black hole growth, their feedback with galaxy formation and evolution, and the timescale of accretion before and after the mergers, are key questions that link the BH astrophysics and cosmology. In my talk, I will review the recent observational and theoretical developments in this topic.
type: talk slot: Monday, 14:35-15:00
Tomasz Kazimierczak – Nicolaus Copernicus University
Title: Kinematical backreaction in cosmological N-body simulations.
Abstract: Scalar averaging is an approach of describing inhomogeneous structure of the Universe. We investigate this approach by testing the consistency of cosmological N-body simulations when they evolve non-linear structures. Using the Delaunay Tessellation Field Estimator (DTFE) we calculate the kinematical backreaction “Q” from Newtonian simulations on different scales and statistically compare its behaviour with analytical relativistic approximations and solutions, in order to measure how much current N-body simulations should be corrected for this effect. This is the first step in a project aimed at developing relativistic N-body simulations.
type: talk slot: Thursday, 16:50-17:05
Magdalena Krupa – Astronomical Observatory of the Jagiellonian University
Title: Galaxy – Star – Quasar separation in the infrared WISE data – poster
Abstract: The goal of our work, which I wish to present in the form of a poster, was to separate effectively galaxies, stars and quasars in the infrared WISE all-sky survey data. The difficulty of this task is related to two things: (i) large numbers – the WISE all-sky database contains photometric and positional information for 563 million objects and (ii) the fact that for many of these sources only limited information in the infrared is available. The technique we employed to classify the WISE sources was based on the Support Vector Machines (SVM). To create training samples for the classifier, and to perform further tests, we used the data set obtained by cross-correlation of the WISE catalogue with the 10th Release of the Sloan Digital Sky Survey database (SDSSxWISE). Since it is technically impossible to use all the available data, we tested what the optimal number of the sources in the training sample is, to ensure both high efficiency of the trained classifier and the reasonable use of the computer resources. We found that the optimal size of the training sample is around 9,000: ∼ 3,000 for each of three classes of sources. The best performance of the classifier is reached when three parameters (W1, W1−W2 and w1mag1−w1mag3) are used. The classifier trained using these three parameters ensures the completeness of the obtained galaxy sample at the level higher than 90%.
type: poster slot: Tuesday poster session 17:20-17:35
Bogna Kubik – IPNL
Title: Universal Nature of subhalo accretion in Warm and Cold DM Cosmologies
Abstract: We examine the angular infall pattern of subhaloes onto host haloes in the context of the large-scale structure in two different cosmologies: Warm and Cold Dark Matter Cosmology. We find that in both scenarios the infall pattern is essentially driven by the shear tensor of the ambient velocity field and the dark matter subhaloes are preferentially accreted along the principal axis of the shear tensor which corresponds to the direction of weakest collapse. We compare the dependence of this preferential infall on subhalo mass, host halo mass and redshift in the two cosmological scenarios.
type: talk slot: Wednesday, 12:05-12:20
Guilhem Lavaux – IAP Paris
Title: Modern reconstruction techniques of the non-linear dynamics of Large Scale Structures
Abstract: In this talk I will present a review of a number of reconstruction techniques of the non-linear dynamics of the Large Scale Structures. This field has now more than a 30 year old history and has been significantly growing recently. I will briefly remind the historical reconstructions given by linear theory, least-action methods, the MAK reconstruction and POTENT method. I will show some recent results still obtained thanks to these methods. Then I will move to modern forward modelling methods (e.g. VIRBIUS, ARES, BORG). I will detail their assumptions and their capabilities. Finally I will present quantitative results obtained on actual data (2M++ and SDSS main sample).
type: talk slot: Tuesday, 10:45-11:10
Baojiu Li – ICC Durham University
Title: TBA
Abstract: TBA
type: talk slot: Thursday, 14:00-14:35
Noam Libeskind – Leibniz Institute for Astrophysics Potsdam
Title: Planes of satellite galaxies and the cosmic web
Abstract: Recent observational studies have demonstrated that the majority of satellite galaxies tend to orbit their hosts on highly attended, vast, possibly co-rotating planes. Two nearly parallel planes of satellites have been confirmed around the M31 galaxy and around the Centaurus A galaxy, while the Milky Way also sports a plane of satellites. It has been argued that such an alignment of satellites on vast planes is unexpected in the standard (CDM) model of cosmology if not even in contradiction to its generic predictions. Guided by LCDM numerical simulations, which suggest that satellites are channelled towards hosts along the axis of the slowest collapse as dictated by the ambient velocity shear tensor, we re-examine the planes of local satellites systems within the framework of the local shear tensor derived from the Cosmic ows-2 dataset. The analysis reveals that the Local Group and Centaurus A reside in a filament stretched by the Virgo cluster and compressed by the expansion of the Local Void. Four out of five thin planes of satellite galaxies are indeed closely aligned with the axis of compression induced by the Local Void. Being the less massive system, the moderate misalignment of the Milky Way’s satellite plane can likely be ascribed to its greater susceptibility to tidal torques, as suggested by numerical simulations. The alignment of satellite systems in the local universe with the ambient shear field is thus in general agreement with predictions of the LCDM model.
type: talk slot: Wednesday, 09:30-09:55
Aaron Ludlow – ICC Durham Univeristy
Title: The Structure of Warm and Cold Dark Matter Halos
Abstract: I will discuss the formation and structure of low-mass dark matter halos that form in Universes dominated by cold (CDM) and warm dark matter (WDM) particles. Differences in the particle nature of dark matter give rise to distinct evolutionary features and impact the structural properties of halos, both of which may have implications for observations sensitive to its small-scale clustering. The suppressed power implicit in WDM models imposes a physical scale on their formation histories, breaking the self-similarity of CDM halo growth and structure. I will discuss possible avenues for modelling the non-linear structure of both CDM and WDM halos directly from the density fluctuation power-spectrum.
type: talk slot: Wednesday, 14:00-14:25
Ewa L. Łokas – Nicolaus Copernicus Astronomical Center, PAS
Title: Tidally induced bars in galaxies
Abstract: The fraction of barred galaxies appears to be larger in the centers of clusters than in the outskirts. We propose to explain the origin of this relation as due to the tidal interactions of disky galaxies with the cluster potential. To support the proposal we performed N-body simulations of the evolution of a Milky Way-like galaxy in a Virgo-like cluster. The disky galaxy was placed on three orbits, of the same eccentricity but different size. For all orbits, the galaxy, although stable against bar formation in isolation, forms a tidally induced bar. The bar forms faster and is stronger for tighter orbits. I will discuss the properties of these tidally induced bars, including their strength, length and the occurrences of the buckling instability. I will also compare their properties to similar phenomenon occurring in dwarf galaxies orbiting the Milky Way.
type: talk slot: Monday, 10:35-11:00
Ryu Makiya – University of Tokyo
Title: The nu2GC model: the galaxy formation model with the largest cosmological N-body simulation
Abstract: Understanding the formation and evolution history of galaxies is one of the main topic of astrophysics. Although the physical properties of galaxies themselves are interesting topic, it is also important as a probe of the observational cosmology. In this talk we present our cosmological galaxy formation model, the nu2GC model, which is the updated version of the nuGC model (Nagashima et al. 2005). Our model is the so-called “semi-analytic model”, in which the formation history of dark matter halos are computed by N-body simulation while the complicated physics of baryons are simply modeled by phenomenological equations. The N-body simulations of dark matter haloes adopted in our model (Ishiyama et al. 2015; the largest simulation consists of 550 billion particles in a box of 1.12 Gpc/h) have unprecedented box size and mass resolution, which enables us to study the more smaller objects and the more rare objects. By using our model, we have constructed the mock catalog of galaxies and AGNs. We will compare the model results with the latest observations, such as luminosity functions, gas mass functions, and blackhole mass functions. We also give some predictions for future facilities such as TMT, SPICA, and JWST.
type: talk slot: Monday, 16:50 – 17:05 Tuesday 12:20 – 12:35
Katarzyna Małek – National Centre for Nuclear Research
Title: A support vector machine classification at the service of VIPERS survey
Abstract: We would like to present the power of Support Vector Machines (SVM) algorithm which are able to separate three-classes of astronomical sources (galaxies, AGNs, and stars) based on the broad-band photometry (CFHTLS). We used as a training set in 5D colour space objects with the best quality spectra from VIPERS and VVDS data. After careful selection of training sample we performed a self-check test of our algorithm for 16,000 objects. Then we applied the same method to the whole VIPERS PR-1 sample (more than 55,000 sources, redshift range between 0.4 to 1.2). Moreover, we used SVM algorithms to find NLAGNs in VIPERS survey, which are not directly observed by VIPERS, using zCOSMOS sample as a training set for SVM classifier. We would like to discuss the future applications of learning algorithms at the service of excellent classifier needed for statistical study of galaxy formation and evolution in the space of different epochs. We conclude that application of the SVM algorithm can deliver an excellent separation between different classes of objects, and this method outperforms simple colour-colour selection methods. We would like to stress that learning algorithms can be regarded as a very efficient classification method particularly suitable for modern large surveys.
type: talk slot: Friday, 14:35-14:40
Justyna Modzelewska – Nicolaus Copernicus Astronomical Center of the PAS
Title: Dark energy and bright quasars
Abstract: Dark energy is one of the most interesting topic in modern Astronomy after discovery that the expansion of the Universe seems to accelerate. Precise measurement of this effect is a key to understand the nature of this medium and we need good probes to do that. Quasars are the brightest part of active galactic nuclei population. Those objects are detected in wide range of redshift. They can be used to track the history of the expansion of the Universe (Watson et al. 2011, Czerny et al. 2013, Marziani & Sulentic 2013, 2014). The use of quasars is based on determination of their redshifts and, independently, their absolute luminosities. This last quantity, combined with the observed luminosity, allows to obtain the distance to an individual quasar. Thus for each source we have independently the distance and the velocity (from redshift), i.e. the Universe expansion rate. The method is essentially equivalent to the use of the SN Ia but it is important to have several independent tracers as each of them has specific, hard to estimate, systematic errors. The project in which I am involved uses the intermediate redshift quasars using 11-m SALTelescope. Determination of the quasar absolute luminosity comes from the measurement of the time delay between one of the strong emission lines and a continuum. MgII is suitable for sources with redshift between 0.4-1.5. I will present new results from the dedicated spectroscopic monitoring being currently performed by our team using Mg II line. High-quality spectra from SALT allow for a very detailed modelling of the line shape and revile potential sources of the systematic errors. Finally, I will summarize all pros and cons of various recently proposed quasar-based methods of the measurement of the dark energy content of the Universe.
type: talk slot: Monday, 15:35-15:50
Masahiro Nagashima – Bunkyo University
Title: The physical origin of the Tully-Fisher relation in the nu2GC model of semi-analytic galaxy formation
Abstract: We present the physical origin of the Tully-Fisher (TF) relation, which is known as the scaling relation between the luminosity and the rotation velocity of galactic discs, clarified by using a semi-analytic galaxy formation model named nu2GC (Makiya et al., in preparation). As shown in classical studies, e.g. Faber (1982) and Blumenthal et al. (1984), the TF relation should reflect the power spectrum of density fluctuations of the cold dark matter. However, modern galaxy formation models have revealed that the slope of the TF relation bends for dwarf spirals because of the supernova feedback (e.g., Nagashima et al. 2005). We find that, by introducing a dynamical response to supernova-induced gas removal on galactic discs, a single power-law of the slope of the TF relation can be restored because the dynamical response decreases the rotation velocity of discs.
type: talk slot: Monday, 17:10-17:25 16:50-17:05
Adi Nusser – Technion
Title: Cosmology with Equivalence Breaking and Lorenz Violation
Abstract: TBA
type: talk slot: Tuesday, 14:00-14:40
Io Odderskov – Department of Physics and Astronomy, Aarhus University
Title: Local variations in the angular velocity power spectrum
Abstract: The peculiar velocity field can be used to probe the local large scale structure of the universe. By measuring supernova light curves and the redshifts of their host galaxies, the velocity structure of the local universe can be probed out to great distances with a sky-survey such as LSST. Since the source of peculiar velocities is variations in the density field, cosmological parameters related to the matter distribution can be extracted from the velocity power spectrum. One way to measure this is to determine the angular velocity power spectrum on spheres at different redshifts by making multipole expansions in spherical harmonics. However, the multipole expansion is not unique if there are areas in which one does not have any information about the velocity field, either due to the survey geometry or to the distribution of supernovae. We investigate how these problems can be solved, using mock supernova catalogues produced from N-body simulations to test the methods. Using the same catalogues, we then measure the cosmic variance in the velocity power spectrum by repeating the procedure many times for differently located observers.
type: poster slot: Tuesday poster session 17:20-17:35
Takashi Okamoto – Hokkaido University
Title: Chemical enrichment of passive galaxies in cosmological simulations of galaxy formation
Abstract: Observationally, massive early-type galaxies have a high metallicity and a higher ratio of alpha elements to iron than their less massive counterparts. Reproducing the latter correlation has long been a severe problem for hierarchical galaxy formation models and cosmological hydrodynamic simulations. We show that the simulations with the quenching of gas cooling in massive dark matter haloes, such as radio-mode AGN feedback, naturally reproduce the observed trend seen between alpha/Fe and the velocity dispersion of galaxies. In our simulations, more massive galaxies are quenched earlier and have older stellar age than less massive galaxies. We conclude that any mechanisms that can explain the galaxy downsizing automatically reproduce the observed trend between alpha/Fe and the velocity dispersion. We however find a new problem in a stellar mass-metallicity relation of the passive galaxies in the simulations. The metallicity of the simulated passive galaxies is lower than that of the star-forming galaxies for a given stellar mass. This apparent conflict with the observations seems to be originated by our phenomenological modelling of the stellar feedback, in which, the mass loading and the speed of a galactic wind are scaled with the velocity dispersion. This type of feedback is widely used both in semi-analytic models and galaxy simulations, and thus this problem must be common to them. We discuss possible solutions to this problem.
type: talk slot: Monday, 16:30-16:45
Jan Ostrowski – Nicolaus Copernicus University
Title: Relativistic Zel’dovich approximation and its applications
Abstract: The relativistic analogue of the widely used Zel’dovich approximation that has been developed by Buchert et al is potentially a very powerful tool for investigating large scale structure formation in the language of general relativity. Expressing the Einstein equation in a synchronous gauge with only one variable object – the Cartan coframe – allows us to construct a relativistic analogy of the classical Zel’dovich approximation by choosing a specific, perturbative form of the geodesic followed by a fluid element. This assumed form of the Cartan coframe is then put into the Einstein equations, and without any further truncations or linearizations, is used to recover non-linear aspects of structure formation with a very small set of assumptions. In particular, the Relativistic Zel’dovich Approximation (RZA) can serve as a closure condition for generalized Friedman equations, provided that a suitable choice of background model has been made. Some applications to cosmological mass function theory will be presented.
type: talk slot: Thursday, 16:30-16:45
Susana Pedrosa – IAFE
Title: Angular momentum evolution for galaxies in a Λ-CDM scenario
Abstract: Galaxy formation in the current cosmological paradigm is a very complex process where inflows, outflows, interactions and mergers are common events. These processes can redistribute the angular momentum content of baryons. Recent observational results suggest that disc formed conserving angular momentum while elliptical galaxies, albeit losing angular momentum, determine a correlation between the specific angular momentum of the galaxy and the stellar mass. We aim at analysing the specific angular momentum content of the disc and bulge components as a function of virial mass, stellar mass and redshift. We also estimate the size of the simulated galaxies and confront them with observations. We use cosmological hydrodynamical simulations that include an effective, physically-motivated Supernova feedback which is able to regulate the star formation in haloes of different masses. We analysed the morphology and formation history of a sample of galaxies in a cosmological simulation by performing a bulge-disc decomposition of the analysed systems and their progenitors. The angular momentum content of the stellar and gaseous discs, stellar bulges and total baryons are estimated. In agreement with recent observational findings, our simulated galaxies have disc and spheroid components whose specific angular momentum contents determine correlations with the stellar and dark matter masses with the same slope, although the spheroidal components are off-set by a fixed fraction. The total specific angular momentum of galaxies do occupy different positions filling the gap between pure rotational-dominated and dispersion-dominated systems. The scaling relations derived for the simulated galaxies determine a similar relation with the virial radius in agreement with recent observations.
type: talk slot: Monday, 12:00-12:25
Christophe Pichon – Institut Astrophysique de Paris
Title: Spin alignments within the cosmic web: a theory of constrained tidal torques near filaments
Abstract: The geometry of the cosmic web drives in part the spin acquisition of galaxies. This can be explained in a Lagrangian framework, by identifying the specific long-wavelength correlations within the primordial Gaussian random field which are relevant to spin acquisition. Tidal Torque Theory is revisited in the context of such anisotropic environments, biased by the presence of a filament within a wall. The point process of filament-type saddles represents it most efficiently. The constrained misalignment between the tidal and the inertia tensors in the vicinity of filament-type saddles simply explains the distribution of spin directions.
type: talk slot: Thursday, 10:05-10:30
Agnieszka Pollo – Astronomical Observatory of the Jagiellonian University and National Centre for Nuclear Research
Title: The VIPERS Survey
Abstract: The “VIMOS Public Extragalactic Redshift Survey” (VIPERS) is an ongoing ESO Large Program to map in detail the spatial distribution of normal galaxies over an unprecedented volume of the z~1 Universe. The measurements of its almost 100,000 galaxies have recently been completed. I will present the overview of the project and its most recent results.
type: talk slot: Friday, 13:30 -14:00
Maciej Remiszewski, Maciej Cytowski – ICM Warsaw University
Title: Addressing Challenges of Data-Intensive Research
Abstract: Building on 20+ years of experience in High Performance Computing, as well as more than a decade of involvement in open science developments (open data and e-infrastructures), ICM focuses on providing high performance computing, data analytics and visualisation services for science and industry. In this talk we will discuss possible cooperation with ICM, which might be especially interesting for researchers undertaking challenging computational and data-driven projects.
type: talk slot: Wednesday, 15:40-16:05
Andrew Robertson – ICC Durham University
Title: Cosmological Simulations with Self-Interacting Dark Matter
Abstract: The cold dark matter and cosmological constant model (ΛCDM) has been successful at describing the observed large-scale structure. However, reported differences on smaller physical scales between simulations and observations have raised the exciting question of whether one of the two main assumptions about the dark matter, namely that it is cold with low thermal velocities and that it is collisionless, could need revising. We present a new code to investigate the collisional nature of dark matter by simulating `Self Interacting Dark Matter’. Based on the N-Body code GADGET-3 it allows us to implement dark matter interactions in a cosmological setting. We show the results of zoom simulations within cosmological boxes, as well as simulations of idealised mergers in which the bulk flow of dark matter leads to a preferred direction along which dark matter particles scatter. Our results suggest potential new observational probes to test the interaction properties of dark matter.
type: talk slot: Wednesday, 14:50-15:05
Boudewijn Roukema – Toruń Centre for Astronomy, Nicolaus Copernicus University
Title: The baryon acoustic oscillation peak: testing the comoving rigidity hypothesis
Abstract: The baryon acoustic oscillation (BAO) peak at about 105 Mpc/h has provided a test of the LambdaCDM standard cosmological model – according to which comoving space is rigid – for about a decade. The BAO peak has been especially useful as a standard ruler for measuring the parameters of the cosmological metric in the context of the same (Friedmann-Lemaitre-Robertson-Walker) family of cosmological models. However, general relativity does not require comoving space to be rigid. During the virialisation epoch during which the most massive structures form by gravitational collapse, it should be expected that comoving space evolves along with structure growth. The BAO peak standard ruler should also follow this evolution if the comoving rigidity assumption is false. The first observational detection of the flexibility of this “ruler” will be presented.
type: talk slot: Thursday, 16:00-16:25
Till Sawala – ICC Durham University
Title: The Local Group: Testing Structure Formation in our Neighbourhood
Abstract: The Local Group and its dwarf galaxies currently represent some of the most discriminating tests of the Lambda-CDM model or its alternatives. Based on results from new cosmological, hydrodynamic simulations of the Local Group, I discuss how the impact of baryons on the masses and substructure of individual halos, as well as the incomplete and selective occupation of low mass halos by galaxies, can affect the assumed relation between the observed dwarf galaxies and the underlying cosmological models.
type: talk slot: Monday, 11:30-11:55
Matthieu Schaller – ICC Durham University
Title: Effects of baryons on the mass and density profiles of halos in LCDM
Abstract: We use the EAGLE suite of cosmological simulations (Schaye+2015, arXiv:1407.7040 ) to investigate the effect of baryons on the halo masses and density profiles. We study how the well-known halo mass functions and halo-mass concentration from simulations evolving solely DM are affected by the presence and interaction of baryons. We find that the halo masses up to 3*10^13 are lowered in the simulation using baryons. This leads to a significant change in the halo mass function (HMF) that evolves with redshift. Precision cosmology measurements unaware of this effect would wrongly conclude that evolving dark energy is required to model the evolution of the HMF. Similarly, we find that the baryons significantly modify the inner parts of halos, creating an increase in the total matter density profile (whilst the DM still follows an NFW profile) that can affect strong lensing measurements. Cosmological probes relying on strong lensing will need to model the baryons more accurately in order to reach the targeted precision in the determination of the cosmological parameters.
type: talk slot: Wednesday, 11:35-12:00
Matthieu Schaller – ICC Durham University
Title: Performance cosmology – the SWIFT code
Abstract: TBA
type: talk slot: Wednesday, 16:30-16:45
Marcin Semczuk – Nicolaus Copernicus Astronomical Center of the PAS
Title: Resonant stirring of disky dwarf galaxies orbiting the Milky Way
Abstract: Tidal evolution of disky satellite galaxies around Milky Way-like hosts is a promising scenario for the formation of dwarf spheroidal galaxies. It also provides a possible partial solution to the missing satellites problem. The dependence of the efficiency of this process on various parameters has been previously investigated. Using N-body simulations we extend these analyses by studying the dependence on the initial inclination of dwarf satellite’s disk with respect to the plane of its orbit around a Milky Way. We find that tidal interactions influence the structure of satellites more strongly if they are on prograde rather than retrograde orbits. For the prograde case the initial disk evolves into a prolate shape, while rotation is replaced by random motions. For the retrograde case the disk retains the oblate shape and the rotation is conserved. Our results suggest that resonant effects are the most important mechanism underlying the evolution while tidal shocking plays only a minor role. We support this hypothesis by comparing the results of simulations to semi-analytical predictions based on the impulse approximation.
type: talk slot: Wednesday, 12:25-12:40
Olga Sergijenko – Astronomical Observatory of Ivan Franko National University of Lviv
Title: Dark-age 21 cm power spectrum in cosmological models with warm dark matter and dynamical dark energy
Abstract: Dark-age 21 cm power spectrum in cosmological models with warm dark matter and dynamical dark energy Olga Sergijenko, Bohdan Novosyadlyj The effect of decaying warm dark matter and dynamical dark energy on the dark-age 21 cm angular power spectrum is studied. Particularly, we consider sterile neutrinos as the dark matter and a scalar field as the dark energy. We take into account the linear effect coming from the perturbations of ionization fractions, matter and spin temperature during Dark Ages. The relative perturbations of Hydrogen and Helium ions number densities have been evolved using the perturbed system of equations for the effective 3-level atom model. The possibility of distinguishing between CDM and sterile neutrino WDM as well as between cosmological constant and scalar field DE using the dark-age 21 cm line tomography is discussed. The comparison with the alternative treatment of perturbed recombination is made.
type: yes slot: Friday, 11:50-12:05
Sergei F. Shandarin – Kanzas University
Title: Multi-stream portrait of the cosmic web
Abstract: The results of the first study of the multi-stream environment of dark matter haloes in cosmological N-body simulations in the lambda cold dark matter cosmology are reported. In our study we use a Lagrangian sub-manifold x = x(q, t) (where x and q are comoving Eulerian and Lagrangian coordinates, respectively), which is dynamically equivalent to the dark matter sheet but is more convenient for numerical analysis. Our major results can be summarized as follows. At the resolution of the simulation, i.e. without additional smoothing, the cosmic web represents a hierarchical structure: each halo is embedded in the filamentary framework of the web predominantly at the filament crossings, and each filament is embedded in the wall-like fabric of the web at the wall crossings. Locally, each halo or sub-halo is a peak in the number of streams field. The number of streams in the neighbouring filaments is higher than in the neighbouring walls. The walls are regions where number of streams is equal to three or a few. Voids are uniquely defined by the local condition requiring to be a single-stream flow region. The shells of streams around haloes are quite thin and the closest void region is typically within one and a half friends-of-friends radius from the centre of the halo.
type: talk slot: Tuesday, 14:35-15:00
Szymon Sikora – Astronomical Observatory, Jagiellonian University
Title: The global disk model of the spiral galaxies. Testing the newtonian gravity.
Abstract: We present the model of the spiral galaxies in which the flat rotation curves are reproduced within the standard newtonian gravity without introducing the nonbaryonic halo. After reconstruction of the mass density distribution of the disk from the rotation curve measurements we checked the consistence with several other observational quantities among of which: the microlensing towards Galaxy center, the motions of distant halo tracer objects of the Milky Way, the vertical gradient of the azimuthal velocity of the Milky Way and several other galaxies, the role of the magnetic field. During the talk I show the details of the presented model and comment on the possible impact of our results on the more popular galactic models with nonbaryonic halo.
type: talk slot: Thursday, 15:10-15:15
Małgorzata Siudek – Center for Theoretical Physics, PAS
Title: VIPERS view of the star formation history of early-type galaxies
Abstract: We present studies over the star formation history (SFH) for different redshift and stellar masses in the range between for early-type galaxies (ETGs) observed by the VIMOS Public Extragalactic Redshift Survey (VIPERS). VIPERS is an ongoing Large Programme to map in detail the large-scale distribution of galaxies at 0.5 < z < 1.2 with a unique volume (24 deg2) and sampling density. The final sample of this survey is going to reach nearly 100,000 galaxies. As the VIPERS sample contains more than 22% of ETGs with known spectroscopic redshift and good quality spectra, it is a perfect sample to study the star formation history based on the spectroscopic features. We used the 4000 Å break strength Dn(4000) and Balmer absorption line strength HδA as diagnostics of the past formation histories of galaxies. These indicators provide important information about the ages of the stellar populations in galaxies and allow to reveal the character of recent star formation histories.
type: talk slot: Friday, 16:00-16:15
Leszek Sokołowski – Astronomical Observatory of the Jagiellonian University
Title: The acceleration of the Universe and alternative theories of gravity
Abstract: We critically review some concepts underlying current applications of gravity theories with Lagrangians being arbitrary scalar functions of the curvature tensor to cosmology to account for the accelerated expansion of the universe. We argue that one cannot reconstruct the Lagrangian from astronomical observations either in cosmology or in the solar system since the Robertson–Walker spacetime is so simple and “versatile” that any cosmic evolution may be fitted by infinite number of various Lagrangians. Any gravity theory different from general relativity generates a new cosmological theory and all the successes of the standard cosmological model are lost even if a single solution of the theory well fits the observations. We emphasize that the current ,,cosmological approach” to the search for the correct gravity theory is conceptually inconsistent: the researchers do seek for a substantial departure from general relativity and on the other hand they do not take into account that a distinct theory will give predictions radically different from those of GR outside the domains of cosmology and solar system effects.
type: talk slot: Thursday, 14:40-15:05
Aleksandra Solarz – National Centre for Nuclear Research
Title: Clustering of mid-infrared selected galaxies
Abstract: We present a method of selection of 24 μm galaxies from the AKARI North Ecliptic Pole (NEP) Deep Field down to 150 μJy and measurements of their two-point correlation function. We aim to associate different 24 μm selected galaxy populations with present day galaxies, and to investigate the impact of their environment on the direction of their subsequent evolution. We discuss the use of Support Vector Machines (SVM) algorithms applied to infrared photometric data to perform star-galaxy separation, in which we achieve an accuracy higher than 80%. The photometric redshift information (obtained through the CIGALE code) is used to explore the redshift dependence of the correlation function parameters (r0) as well as the linear bias evolution (which relates galaxy distribution to the one of the underlying dark matter). We connect the investigated sources to their potential local descendants through simplified model of the clustering evolution without interactions.
type: talk slot: Friday, 14:55 – 15:10
Elmo Tempel – Tartu Observatory
Title: Galactic filaments in the cosmic web: alignment of satellite galaxies and galaxy pairs
Abstract: During last years several new and improved algorithms have been proposed for cosmic cartography. One of them is Bisous model (Tempel et al. 2014a) that uses the marked point process to detect the filamentary pattern in the cosmic web. This method have already used in several papers (Guo et al. 2015; Tempel et al. 2014b,c; Tempel & Libeskind 2013) to analyse the connection between cosmic web filaments and galaxies. In my talk I will present the recent results, where we analysed the alignment of satellite galaxies and galaxy pairs in filaments. Our study is based on the SDSS data. For satellite alignment we combine the spectroscopic and photometric redshift catalogues that increases the number of satellite galaxies considerably. To study the galaxy pair alignment in filaments, we use the friend-of-friend group catalogue constructed in Tempel et al. (2014d). Our results indicate that both, satellite galaxies and galaxy groups, are aligned with galactic filaments. The alignment is up to 6.5sigma for galaxy pairs. Our results give new insight into the formation and evolution of galaxies and galaxy groups. Particularly, our results show that there is strong connection between the morphology of cosmic web and galaxy/group formation. References: Guo, Q., Tempel, E., & Libeskind, N. I. 2015, ApJ, 800, 112 Tempel, E. & Libeskind, N. I. 2013, ApJ, 775, L42 Tempel, E., Stoica, R. S., Martínez, V. J., et al. 2014a, MNRAS, 438, 3465 Tempel, E., Libeskind, N. I., Hoffman, Y., Liivamägi, L. J., & Tamm, A. 2014b, MNRAS, 437, L11 Tempel, E., Kipper, R., Saar, E., et al. 2014c, A&A, 572, A8 Tempel, E., Tamm, A., Gramann, M., et al. 2014d, A&A, 566, A1
type: talk slot: Thursday, 12:20-12:35
Cora Uhlemann – LMU Munich
Title: Edgeworth streaming model for redshift space distortions
Abstract: We derive the Edgeworth streaming model (ESM) for redshift space distortions starting from an arbitrary distribution function for biased tracers of dark matter. We test the accuracy of the GSM and ESM independent of perturbation theory using an N-body halo catalog. While the redshift space monopole is well described by the GSM, the ESM pushes the 2% accuracy of the GSM from 30 Mpc/h down to 10 Mpc/h for higher multipoles. To predict the scale dependent functions entering the streaming model we employ Convolution Lagrangian perturbation theory (CLPT) and local Lagrangian bias. Since dark matter halos carry an intrinsic length scale given by their Lagrangian radius, we extend CLPT to the coarse-grained dust model. The coarse-graining is performed in the initial conditions with subsequent dust dynamics, implemented by smoothing the initial power spectrum in the spirit of the truncated Zel’dovich approximation. We compare the predictions to N-body measurements and comment on the proper choice of the smoothing scale to optimize the combined predictions for the redshift space halo correlation function.
type: talk slot: Friday, 11:30-11:45
Rien van de Weygaert – Kapteyn Institute, University of Groningen
Title: the Infrastructure of Voids – on Void Hierarchy, Void Galaxies and the Local Void
Abstract: I will review the hierarchical evolution of voids, discussing how they build up the void population via the processes of merging and collapse. On the basis of the Multiscale Watershed Void Finder we investigate the systematics of void evolution in adhesion models of structure formation. Subsequently, we follow the evolution of walls, filaments and haloes in the interior of void regions in the high-resolution LCDM CosmoGrid simulation. The results will be connected to the filamentary void galaxy configuration VGS31 in SDSS. Finally, we turn towards the structure Local Void, and follow its dynamical evolution on the basis of an adhesion-based reconstruction of the Cosmic Web in the local Universe.
type: talk slot: Thursday, 09:30-10:00
Radosław Wojtak – KIPAC
Title: Tracing the evolution of cosmic voids
Abstract: I will present a new technique for tracing redshift evolution of voids in cosmological simulations with cold dark matter. The method finds progenitors of voids by tracking watershed basins of the density field. The watershed basins are grouped into voids at redshift z=0 and mapping between voids and their progenitors is performed by identifying basins of z=0 voids at higher redshifts. The method allows for a robust finding of voids’ progenitors at all redshifts going all the way to initial conditions. The main focus of my talk will be on presenting some applications of the new method. I will show evolution of several properties of voids such as effective radii, density profiles, shapes, relative orientations of principle axes (alignments of principle axes of the shape tensor). I will discuss to what degree some properties of voids are born in the primordial density field and thus they are already present in initial conditions, and to what degree they are modified by tidal forces in the epoch of non-linear evolution.
type: talk slot: 11:50-12:15
Saleem Zaroubi – Kapteyn Institute, University of Groningen
Title: Intensity mapping of large scale filaments with Radio telescopes
Abstract: Intensity mapping signal of both hyperfine transitions of HI and 3HeII from large-scale filamentary structures is estimated. Although both species are mostly ionized in the IGM, the balance between ionization and recombination in moderately high-density regions renders them abundant enough to be observed. H I in filaments is possibly observable even with current telescopes after 100 h of observation. On the other hand, 3He II is only detectable with future telescopes, such as Square Kilometre Array, after the same amount of time. I discuss (MISSING)
type: talk slot: Thursday, 10:35-10:50
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