Site Map
Follow us on Facebook Follow us on Twitter YouTube channel
Centro de Astrofísica da Universidade do Porto
31 August to 6 September 2011, Angra do Heroísmo, Azores, Portugal


Dark energy theory & observations
Bruce Bassett (Cape Town)

The lectures will cover evidence for cosmic acceleration, particularly Baryon Acoustic Oscillations, as well as models of dark energy and open research questions in these areas.



Limits on Dark Radiation, Early Dark Energy, and Relativistic Degrees of Freedom
Ermínia Calabrese (Roma)

Recent cosmological data analyses hint at the presence of an extra relativistic energy component in the early universe. This component is often parametrized as an excess of the effective neutrino number N_{eff} over the standard value of 3.046. The excess relativistic energy could be an indication for an extra (sterile) neutrino, but early dark energy and barotropic dark energy also contribute to the relativistic degrees of freedom. We examine the capabilities of current and future data to constrain and discriminate between these explanations, and to detect the early dark energy density associated with them. We found that while early dark energy does not alter the current constraints on N_{eff}, a dark radiation component, such as that provided by barotropic dark energy models, can substantially change current constraints on N_{eff}, bringing its value back to agreement with the theoretical prediction. Both dark energy models also have implications for the primordial mass fraction of Helium Y_p and the scalar perturbation index n_s. The ongoing Planck satellite mission will be able to further discriminate between sterile neutrinos and early dark energy.



Analysis of SDSS-II Supernova with SDSS-III, Baryon Oscillation Spectroscopic Survey (BOSS) host galaxy redshift
Heather Campbell (Portsmouth)

I will present the analysis of 709 Type Ia Supernovae (SNe Ia) from the SDSS-II Supernovae Survey, with host galaxy redshifts from the Baryon Oscillation Spectroscopic Survey (BOSS). I will describe the method I have developed to photometrically classify SNe Ia that lack a supernova spectrum, but includes the host spectroscopic redshift as a prior in the photometric typing. I have compiled a sample of well-trusted SNe Ia (less than 3% contamination), which I have used to build the largest SN Hubble diagram to date selected from a single survey, namely the SDSS. I will talk about the cosmological parameters fits for this data-set and discuss potential bias in the sample which I have been investigating using simulated sampled of SDSS supernovae. These bias effects include classification uncertainties and Malmquist bias from the SNe Ia and their host galaxies.



High-z massive clusters and non standard cosmological models
Edoardo Carlesi (Madrid)

I would like to talk about the use of observation of massive clusters at z>1 as a test for the LambdaCDM model and for alternative cosmologies, such as Vector Dark Energy (VDE) and Coupled Quintessence. In particular, I would like to focus on my work, in which - by means of a series of N-body simulations - I have studied the properties of large scale clustering in the VDE scenario compared to the standard LambdaCDM one.



Fast methods to detect non-Gaussianities in CMB data
Biuse Casaponsa (Cantabria)

Different methods to test CMB Gaussianity and to constrain the local non-linear coupling parameter fNL in WMAP data will be presented. The development of fast methods for analysis which imply the computation of the third order moments of the CMP temperature fluctuations is crucial due to the new data coming from PLANCK. The talk will be a summary of the methods we have been using and a comparison with the ones already in use as the bispectrum, Minkowsky functionals, wavelets,etc. The methods presented are based on a fast wavelet decomposition, a neural network classifier to avoid matrix inverstions, and the binned bispectrum proposed by Bucher et al. 2010.



Physical properties of type Ia supernovae and cosmological applications
Flora Cellier-Holzem (LPNHE)

The use of type Ia supernovae (SNeIa) for cosmology is limited today by systematic uncertainties. To reduce these uncertainties and standardize these objects, we have to better understand their physical properties. For this purpose, I compare SNeIa observed spectra and light-curves from the SuperNova Legacy Survey (SNLS) and SuperNova Factory (SNF) with the predictions of various supernova formation models (W7, delayed detonation models) in order to constrain and improve them.



Alternative models of gravity
Dragan Huterer (University of Michigan)

Currently, all cosmological observations are in concordance with the model where dark energy - the stuff that causes the accelerated expansion - forms 75% of the energy in the universe, while the other 25% is comprised of dark and visible matter, as well as a small admixture of radiation. Therefore we have a twofold grand mystery: What is the origin and nature of dark energy and the accelerating universe? And why is the composition of the universe rather complicated, with dark energy, dark matter, visible matter, and radiation all present and non-negligible today? I will address some - mostly unsuccessful - attempts to explain these questions, and generic approaches to ruling out LCDM model.



Type Ia Supernovae
Alex Kim (LNBL)

Type Ia supernovae were used to discover the accelerated expansion of the universe and continue to be a strong probe of the Dark Energy responsible for that acceleration. These supernovae are standard candles and hence excellent distance indicators that map the expansion history of the universe and measure cosmological parameters. Supernovae are discovered and observed with imagers and spectrographs on optical telescopes. There is now there is a large library of objects used in the cosmological analysis. The distance to a supernova is derived from multi-band light curves. Current results are limited by systematic uncertainties that future surveys plan to address and suppress.



Combining small-scale clustering with WMAP Data to Constrain Models of Dark Energy Dynamics
Michelle Knights (Cape Town)

Recent progress in accurately measuring galaxy clustering allows potentially powerful constraints to be placed on models of dark energy dynamics when combined with the latest WMAP Cosmic Microwave Background (CMB) data. We use a Monte-Carlo Markov Chain to explore the best fits to the CMB and clustering data for various parameters of dark energy dynamics. Thus we can investigate the implications of the small/large scale clustering comparison.



Looking for new physics in the early universe
Carlos Martins (CAUP)

Cosmology and particle physics are presently experiencing a truly exciting period. On the one hand both have remarkably successful standard models, which are in agreement with a plethora of experimental and observational data. On the other hand there are also strong hints that neither of these models is complete, and that new physics may be there, within the reach of the next generation of probes. After reviewing some of these hints I will discuss ways in which astrophysical and cosmological observables can be used to search for new physics. I will present a few examples, focusing on astrophysical measurements of fundamental couplings and other consistency tests of the Lambda-CDM model.



CMB Theory and Fundamental Physics
Alessandro Melchiorri (Roma)

After a brief review of the standard cosmological model, my lectures will focus on the anisotropy of the cosmic microwave background (CMB) radiation (temperature and polarization). I plan to describe what we have learned from current CMB observations and discuss how the CMB can provide precise measurements of the composition and geometry of the observable universe. In the last lecture I will discuss what we may further learn from future CMB measurements , focusing on neutrino physics, variation of fundamental constants, and dark energy.



Constraints on variations of fundamental constants
Eloisa Menegoni (Roma)

I will discuss present and future cosmological constraints on variations of the fine structure constant induced by an early dark energy component having the simplest allowed (linear) coupling to electromagnetism. We find that current cosmological data show no variation of the fine structure constant at recombination respect to the present-day value, with $alpha / alpha_0 = 0.975 +- 0.020 at 95 \%$ c.l., constraining the energy density in early dark energy to $Omega_e < 0.060$ at $95 \%$ c.l.. Moreover, we consider constraints on the parameter quantifying the strength of the coupling by the scalar field. We find that current cosmological constraints on the coupling are about 20 times weaker than those obtainable locally (which come from Equivalence Principle tests). However forthcoming or future missions, such as Planck Surveyor and CMBPol, can match and possibly even surpass the sensitivity of current local tests.



Parameterization Effect in the Analysis of Sunyaev- Zel'dovich observations with Arcminute Mickrokelvin Imager
Malak Olamaie (Cambridge)

Current studies of the Sunyaev-Zel'dovich (SZ) effect are based on parameterized models of galaxy clusters. Investigating the effects of different parameterizations and the assumptions made within any parameterized model are, therefore, crucial in extracting cluster physical properties in a robust way. In this talk I discuss three different parameterizations that one could take to analyze the SZ effect from galaxy clusters within a particular model and demonstrate how each parameterization introduces different constraints and biases in the posterior probability distribution of inferred cluster parameters.



Cosmology with ESPRESSO & CODEX
Paolo Molaro (Trieste)

I will describe briefly the ESO projects for the new generation of high resolution spectrographs ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) for the incoherent combined 4VLT focus and CODEX (Cosmic Dynamics EXperiment) for the E-ELT. Then i'll discuss their main cosmological drivers:
i) the variability of fundamental constants by means of qso absorption lines: motivation, measurable constants, techniques and present status.
ii) the measure of the acceleration of the Universe by monitoring the cosmological redshift drift of spectroscopic features at cosmological distances: concept and feasibility.



Early astrophysics results from Planck
Graça Rocha (JPL/Caltech)

On 11th of January of 2011 ESA, NASA and the Planck Collaboration announced the delivery to the public of the Early Release Compact Source Catalog, ERCSC, together with a set of 25 scientific papers, which can be accessed by the community from the Planck Legacy Archive. This talk will give an overview of the main early astrophysics results from Planck presented in these early papers.



Gravitational waves
Bernard Schutz (Max Planck Institute)

Lecture 1 - Elementary Theory of Gravitational Waves and their Detection
Linearized gravitational waves in general relativity, how to measure curved geometry and gravitational tidal forces using radar. Review of current and proposed gravitational wave detectors (LIGO, VIRGO, GEO, LCGT, LISA, and pulsar timing). What observations are likely, what information is contained in the waves. Analogy with detecting sound waves.

Lecture 2 - Gravitational Waves from Binary Systems: Probes of the Universe
Quadrupole radiation and higher corrections from binaries, tests of general relativity, binaries as standard sirens/standard candles. Neutron-star mergers, gamma-ray bursts, and measuring the local Hubble constant. Cosmological information from future detectors, especially about the early history of massive black hole formation.

Lecture 3 - A Stochastic Gravitational Wave Cosmological Background
Stochastic radiation from inflation, phase transitions, and other early-universe physics. Astrophysical backgrounds. How detectors search for backgrounds. Current observational limits from LIGO.



Paul Shellard/James Fergusson (Cambridge)

Lecture 1 - Non-Gaussianity: A new frontier in cosmology
Arguably the most stringent tests of the standard inflationary cosmology relate to its statistical properties beyond the power spectrum: vanilla slow-roll inflation predicts that will be no observable deviations from randomness for the primordial bispectrum (three-point correlator) and trispectrum (four-point correlator). On the other hand, the detection of a significant bi-/trispectrum signal could open up a new window on the early universe, revealing distinct fingerprints of specific fundamental cosmologies.
The purpose of this first lecture is to introduce basic concepts in non-Gaussianity, focussing particularly on the so-called "local" model.
Topics covered will include primordial and CMB bispectra, an overview of their different possible shapes, the CMB bispectrum estimator, emphasising the importance of separability for tractability.

Lecture 2 - General Modal Approach to Non-Gaussian Estimation
New high resolution experiments will place standard inflation firmly in the dock, especially data from the Planck satellite as well as future data from large-scale galaxy surveys. This lecture will describe new modal estimator methods which allow the efficient and optimal extraction of the bispectrum and trispectrum from these large datasets. Starting with a set of separable eigenmodes, we will show how these can be used to describe any theoretical or observational bispectrum. We will apply these expansions to the bispectrum estimator, showing how the observed CMB bispectrum can be reconstructed and how to produce simulated CMB maps for arbitrary bispectra. We will describe how effects of instrumental noise and the beam are accommodated in a practical implementation for the WMAP analysis.

Lecture 3 - Applications: Non-Gaussian analysis of WMAP, Planck and LSS
The third lecture will describe the application of polyspectra estimation methods to WMAP and Planck data analysis, as well as large-scale structure surveys. We will describe how different primordial and contaminant/foreground contributions can be distinguished using a principal mode analysis. We will present WMAP bispectrum and trispectrum constraints on a wide range of primordial and late-time non-Gaussian models and we will discuss related forecasts for Planck. Finally, we will discuss the extension of modal estimation methods for non-Gaussian analysis of galaxy surveys, including the creation of initial conditions for N-body simulations with arbitrary polyspectra.



Merging Rates of the First Objects and the Formation of First Mini-Filaments in Models with Massive Neutrinos
Hyunmi Song (Seoul National University)

We study the effect of massive neutrinos on the formation and evolution of the first filaments composed of the first star-forming halos of mass $Msim 10^{6}M_{odot}$ at $zsim 20$. With the help of the extended Press-Schechter formalism, we evaluate analytically the rates of merging of the first star-forming halos into zero-dimensional larger halos and one-dimensional first filaments. It is shown that as the neutrino mass fraction $f_{ u}$ increases, the halo-to-filament merging rate increases while the halo-to-halo merging rate decreases sharply. For $f_{ u}le 0.04$, the halo-to-filament merging rate is negligibly low at all filament mass scales, while for $f_{ u}ge 0.07$ the halo-to-filament merging rate exceeds $0.1$ at the characteristic filament mass scale of $sim 10^{9}M_{odot}$. The distribution of the redshifts at which the first filaments ultimately collapse along their longest axes is derived and found to have a sharp maximum at $zsim 8$. We also investigate the formation and evolution of the second generation filaments composed of the first galaxies of mass $10^{9}M_{odot}$ at $z=8$. A similar trend is found: For $f_{ u}ge 0.07$ the rate of clustering of the first galaxies into the second-generation filaments exceeds $0.3$ at the characteristic mass scale of $sim 10^{11}M_{odot}$. The longest-axis collapse of these second-generation filaments are found to occur at $zsim 3$. We discuss the implications of our results on the formation of massive high-$z$ galaxies and possibility of constraining the neutrino mass from the mass distribution of the high-$z$ supermassive blackholes.



Bayesian reconstruction of the gravitational potential from weak lensing
Rafal Szepietowski (Portsmouth)

Mass mapping using weak lensing has been a very successful technique in cosmology as proven by the indication of a Dark Matter component in the Bullet Cluster. In this talk I will review the Bayesian approaches to weak lensing potential reconstruction and propose a Maximum-Probability method. I will discuss how to incorporate prior information in the reconstruction process of 2D and 3D maps of the gravitational potential due to large scale structure and show the results of applying this method to N-body simulations.



Photometric calibration of the wide field imager MegaCam with the demonstrator SNDIce
Francesca Villa (LPNHE)

Type Ia Supernovae (SNe Ia) are one of the most powerful cosmological probes to study the properties of Dark Energy.The next generation of very large surveys (DES, Euclid, LSST) will detect and study thousands of SNe Ia. The measurement of the Dark Energy Equation of State will reach a statistical precision of 1% or better. The challenge is now the reduce systematic uncertainties to a comparable level. The dominant contribution to systematic error budget is the photometric calibration of the imagers. The future surveys will require a flux calibration accurate at the per-mil level. This seems difficult to obtain with the traditional technics relying on standard star observations. For this reason supernova surveys are exploring alternatives. For instance, the SNLS collaboration began to invest in the SNDice project. SNDice is a demonstrator, designed and built at LPNHE in Paris, which was installed in 2008 in the enclosure of the Canada-France-Hawaii Telescope (CFHT) in Mauna Kea (Hawaii). The goal is to show that it is possible to obtain a accuracy of 0.1% or better. The instrument is a light source composed of 24 LEDs whose fluxes, from the UV to the IR, have been calibrated with a precision of ? 0.01% using a NIST photodiode. In this talk, we will review the many applications of the SNDice instrument, such as the monitoring of the telescope readout electronics, the study of the camera uniformity and the measurement of the imager passbands.We will detail the analysis of the SNDice data and explain how this strategy may be an alternative to the traditional calibration technics.



Boosting the Universe: Observational consequences of our motion
Amanda Yoho (CWRU)

The Cosmic Microwave Background (CMB), photons from the earliest epoch that are able to free stream towards us, provides a unique opportunity to learn about many properties of the universe we live in. Already, the temperature fluctuations of the CMB have been studied by the Wilkinson Anisotropy Probe (WMAP) and have allowed many cosmological parameters to be pinned down to within a percent error. However, there are many more mysteries to be uncovered by precise measurements of the CMB polarization of these photons and weak lensing fields. Only with a robust understanding of the possible contaminants and astrophysical effects that can deform the measured fields will we be able to accurately characterize which models are favored over others. We will present here the challenges that will arise when analyzing data from future cosmological surveys due to our motion through the universe.