Past Talks @ ICE

Número de entradas: 17

01
Marzo 2017

Modeling the distribution of HI in the post-reionization era: Cosmology with SKA


Inicio: 12:30h
Ponente: Francisco Villaescusa-Navarro (Center for Computational Astrophysics (Simons Foundation, New York))
Lugar: Sala Alberto Lobo

I will discuss the possibility of sampling the large-scale structure of the Universe using radio-telescopes through the 21cm intensity mapping technique in the post-reionization era. I will show how to model the spatial distribution of cosmic neutral hydrogen using numerical simulations and the constraints…
Inicio: 12:30h
Ponente: Francisco Villaescusa-Navarro (Center for Computational Astrophysics (Simons Foundation, New York))
Lugar: Sala Alberto Lobo

I will discuss the possibility of sampling the large-scale structure of the Universe using radio-telescopes through the 21cm intensity mapping technique in the post-reionization era. I will show how to model the spatial distribution of cosmic neutral hydrogen using numerical simulations and the constraints that the Square Kilometre Array (SKA) instrument will place on warm dark matter and massive neutrinos. I will also examine how well the SKA1-MID instrument will be able to detect the BAO. Finally, I will discuss the potential problems such as the presence of bright foregrounds and the role of instrument calibration.
16
Febrero 2017

Sufficient Statistics for Cosmology


Inicio: 12:00h
Ponente: Istvan Szapudi (Institute of Astronomy (University of Hawai))
Lugar: Sala Alberto Lobo

Sufficient statistics extract all the cosmological information from a large scale structure survey, thus they sharpen constraints available from traditional statistics, such as power spectrum. The log-power spectrum, the simplest among the approximations studies to date, will double the effective survey…
Inicio: 12:00h
Ponente: Istvan Szapudi (Institute of Astronomy (University of Hawai))
Lugar: Sala Alberto Lobo

Sufficient statistics extract all the cosmological information from a large scale structure survey, thus they sharpen constraints available from traditional statistics, such as power spectrum. The log-power spectrum, the simplest among the approximations studies to date, will double the effective survey volume of future surveys, such as EUCLID and WFIRST. I will review the theory of sufficient statistics, forecasting, and recent results on predicting the log power spectrum.
26
Enero 2017

Redshift-space distortions - Measuring the growth rate of structures from the final VIPERS dataset


Inicio: 12:00h
Ponente: Andrea Pezzotta (Brera Observatory (Milan))
Lugar: Sala Alberto Lobo

Observations of Type Ia Supernovae combined with the anisotropies of the Cosmic Microwave Background have reinforced the conclusion that our Universe is dominated by a repulsive dark energy capable of driving the observed accelerated expansion. Unfortunately this scenario is highly degenerate with the…
Inicio: 12:00h
Ponente: Andrea Pezzotta (Brera Observatory (Milan))
Lugar: Sala Alberto Lobo

Observations of Type Ia Supernovae combined with the anisotropies of the Cosmic Microwave Background have reinforced the conclusion that our Universe is dominated by a repulsive dark energy capable of driving the observed accelerated expansion. Unfortunately this scenario is highly degenerate with the more radical breakdown of General Relativity on cosmological scales, since modified gravity can predict the same expansion history H(z) as in a LCDM (dark energy+ GR). In principle, this degeneracy can be lifted by measuring the growth rate of structure, which depends on the specific theory describing gravity. One of the most reliable probes of the growth of structures is provided by redshift-space distortions (RSD). These arise when measured redshifts, that contain also the contribution of galaxy peculiar velocities, are used as distance proxy, introducing an anisotropy in the measured clustering.  Unfortunately, extracting the linear RSD signal from galaxy redshift surveys is non-trivial, because much of the RSD signal lies on quasi-linear and non-linear scales. This requires a strong effort to properly model non-linear clustering and velocities. Here I present measurements of the growth rate of structure from the new data of the complete VIPERS survey. We implement and improve specific techniques and models, both to correct for any defects inside the measured 2PCF and also to understand the impact of different RSD models on the recovery of the growth rate.   Measurements of the growth rate from VIPERS are in agreement with standard cosmology predictions assuming Einstein gravity in a LCDM background, although they still do not exclude a variety of models in which gravity is modified on cosmic scales
24
Enero 2017

Photometric redshift estimation for precision cosmology


Inicio: 10:30h
Ponente: markus rau (LMU (Munich))
Lugar: Sala Alberto Lobo

Abstract: Photometric redshift uncertainty is one of the dominant sources of systematic error in ongoing and future large area photometric surveys like DES, KiDS, LSST and Euclid. Accurate photometric redshift validation and treatment of redshift uncertainty is therefore a vital requirement…
Inicio: 10:30h
Ponente: markus rau (LMU (Munich))
Lugar: Sala Alberto Lobo

Abstract: Photometric redshift uncertainty is one of the dominant sources of systematic error in ongoing and future large area photometric surveys like DES, KiDS, LSST and Euclid. Accurate photometric redshift validation and treatment of redshift uncertainty is therefore a vital requirement to enter the era of precision cosmology using these surveys. In my talk I will discuss these challenges and present a Machine Learning based photometric redshift methodology, that uses synthetic data from simulations, templates and spectroscopic data to produce highly accurate photometric redshift predictions. In combination with the Smoothed Bootstrap, a specialized resampling technique, it is then possible to incorporate the remaining photometric redshift error into the cosmological parameter constraint.
23
Enero 2017

Addressing systematic effects in the new generation of galaxy surveys


Inicio: 10:30h
Ponente: Jonás Chaves Montero (CEFCA (Teruel))
Lugar: Sala Alberto Lobo

There is a world-wide effort to unravel the nature of gravity and the expansion history of the Universe. The new generation of cosmological surveys such as DES, PAUS, J-PAS, DESI, LSST, Euclid, WFIRST, etc., will provide tons of data that will no longer be dominated by statistical errors but by systematic…
Inicio: 10:30h
Ponente: Jonás Chaves Montero (CEFCA (Teruel))
Lugar: Sala Alberto Lobo

There is a world-wide effort to unravel the nature of gravity and the expansion history of the Universe. The new generation of cosmological surveys such as DES, PAUS, J-PAS, DESI, LSST, Euclid, WFIRST, etc., will provide tons of data that will no longer be dominated by statistical errors but by systematic uncertainties.  I will study the impact of some of these systematic uncertainties on the large-scale structure. I will address baryonic effects using a new implementation of subhalo abundance matching, a model for connecting dark matter haloes with galaxies, that produces the same galaxy clustering as hydrodynamical simulations within statistical errors. Then, I will show the effect of sub-percent redshift uncertainties on the baryonic acoustic oscillations (BAO). I will provide analytical expressions for their effects and I will show how the cosmological information encoded in the BAO is modulated by the interplay of redshift space distortions, redshift errors, bias, and number density of the sample. Finally, I will present ELDAR, a new method for detecting AGN and computing their redshifts in medium- and narrow-band photometric surveys.
19
Enero 2017

Galaxy formation in the Planck Millennium


Inicio: 12:00h
Ponente: Carlton Baugh (Durham)
Lugar: Sala Alberto Lobo

I will give an overview of semi-analytical modelling of galaxy formation, and show how the model predictions are affected by the uncertainty in the modelling of sub-grid physics, as set out in Lacey et al. (2016). I will then show how the model can be used to make predictions for HI intensity…
Inicio: 12:00h
Ponente: Carlton Baugh (Durham)
Lugar: Sala Alberto Lobo

I will give an overview of semi-analytical modelling of galaxy formation, and show how the model predictions are affected by the uncertainty in the modelling of sub-grid physics, as set out in Lacey et al. (2016). I will then show how the model can be used to make predictions for HI intensity mapping experiments.  
20
Diciembre 2016

Special Christmas Talk: What can and cannot be said about randomness using quantum physics?


Inicio: 11:30h
Ponente: Antonio Acín (ICFO)
Lugar: Sala Alberto Lobo, ICE

It is usually said that quantum physics is, contrary to classical physics, intrinsically random. The intrinsic randomness of quantum physics follows from the fact that it is possible to observe correlations among quantum particles for which there exists no classical and deterministic model. The observation…
Inicio: 11:30h
Ponente: Antonio Acín (ICFO)
Lugar: Sala Alberto Lobo, ICE

It is usually said that quantum physics is, contrary to classical physics, intrinsically random. The intrinsic randomness of quantum physics follows from the fact that it is possible to observe correlations among quantum particles for which there exists no classical and deterministic model. The observation of these correlations, however, requires some assumptions about the setup. In particular, it requires some initial randomness, which makes the whole argument apparently circular. We discuss how it is possible to relax this circularity and conclude that an intrinsic form of randomness with no classical analogue does exist in the quantum world.
14
Noviembre 2016

Sun and water as means of sustainable development: cases from Honduras and Uganda


Inicio: 12:00h
Ponente: Daniele Vigano (CIRPS / Sapienza University / Work System srl, Rome)
Lugar: Sala Alberto Lobo

The access to electricity in developing countries is very limited, being almost non-existent in the rural areas: in 2016, still 1.5 billions people (20% of the world population) are without light. This represents a mayor obstacle to the sustainable development and to the economical empowerment, and prevents…
Inicio: 12:00h
Ponente: Daniele Vigano (CIRPS / Sapienza University / Work System srl, Rome)
Lugar: Sala Alberto Lobo

The access to electricity in developing countries is very limited, being almost non-existent in the rural areas: in 2016, still 1.5 billions people (20% of the world population) are without light. This represents a mayor obstacle to the sustainable development and to the economical empowerment, and prevents the spread of effective basic health and educational services. Here we present two realized projects which central focuses are the construction of small off-grid renewable energy-based power plants and their smart distribution grids that serve the rural communities of El Dictamo (Olancho, Honduras) and Kitobo Island (Kalangala, Lake Victoria, Uganda). Besides the technical issues, we focus on the peculiar local context and on the experience lived on the field.
27
Octubre 2016

Void dynamics as a probe of cosmology and gravity


Inicio: 12:00h
Ponente: Nico Hamaus (Ludwig-Maximilians-Universität (LMU))
Lugar: Sala Alberto Lobo (ICE)

Redshift surveys measure the location of millions of galaxies in the observable Universe, thereby constructing a three-dimensional map of its large-scale structure. This structure is characterized by dense clusters of galaxies, connected by filaments and sheets of lower density. The remaining and dominant…
Inicio: 12:00h
Ponente: Nico Hamaus (Ludwig-Maximilians-Universität (LMU))
Lugar: Sala Alberto Lobo (ICE)

Redshift surveys measure the location of millions of galaxies in the observable Universe, thereby constructing a three-dimensional map of its large-scale structure. This structure is characterized by dense clusters of galaxies, connected by filaments and sheets of lower density. The remaining and dominant volume within this cosmic web is taken up by voids, vast regions of relatively empty space. I will highlight some recent advances in modeling average void density and velocity profiles, as well as their anisotropic shapes in redshift space on the basis of simulations and mock galaxy catalogs. While clusters, filaments and sheets have entered various stages of nonlinearity in the past, voids represent structures whose dynamic evolution can be described remarkably well by linear theory, suggesting them to be among the most pristine objects to consider for future studies on the nature of dark energy, dark matter and gravity. I will present first results in this context, obtained via the analysis of galaxy survey data from the Sloan Digital Sky Survey.
20
Octubre 2016

Multi-messanger probes of neutron star superfluidity


Inicio: 11:00h
Ponente: Bryn Haskell (Nicolaus Copernicus Astronomical Centre, Warsaw (Poland))
Lugar: Sala Alberto Lobo

With a mass approximately equal to that of the sun compressed in a 10 km radius, the interior densities of neutron stars easily surpass nuclear saturation density, thus making them one of the most interesting and exotic nuclear physics laboratories in the universe. At such densities the Fermi energy…
Inicio: 11:00h
Ponente: Bryn Haskell (Nicolaus Copernicus Astronomical Centre, Warsaw (Poland))
Lugar: Sala Alberto Lobo

With a mass approximately equal to that of the sun compressed in a 10 km radius, the interior densities of neutron stars easily surpass nuclear saturation density, thus making them one of the most interesting and exotic nuclear physics laboratories in the universe. At such densities the Fermi energy is much higher than the thermal energy, and despite interior temperatures of above 10^7 K, these objects behave as cold objects.This leads to large-scale superfluid components in the interior, which have a profound impact on the dynamics of the star, which now has to be modelled as a system of multiple inter-penetrating fluids. In this talk I will review various aspects of neutron star superfluidity, and describe how such physics on the microscopic scale can lead to macroscopic, observable, astrophysical phenomena. In particular I will focus on radio pulsar glitches, and gravitational waves from unstable modes of oscillation of the star, and describe future directions and applications of the formalism.  
12
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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya