CosmosClub: Celine Gouin (20/02/20)

Date: February 20th 2020, 10.00 am

Room: Kepler

Speaker: Céline Gouin (IAS, COSMIX)

Title: Probing the azimuthal environment of galaxies around clusters. From cluster core to cosmic filaments

Abstract:  

Galaxy clusters are connected at their peripheries to the large scale structures by cosmic filaments that funnel accreting material.Therefore, the vicinity of galaxy clusters are ideal places to quantify the geometry and topology of the cosmic web.These filamentary structures are studied to investigate both environment-driven galaxy evolution and the growth of massive structures. In this presentation, I probe angular features in the distribution of galaxies around clusters by performing harmonic decompositions in large photometric galaxy catalogues around low-z clusters. In the clusters’ outskirts, filamentary patterns are detected in harmonic space: massive clusters seem to have a larger number of connected filaments than low-mass ones. Our results suggest also a gradient of galaxy activity in filaments around clusters.

CosmosClub: Miguel Zumalacarregui (06/11/19)

Testing Gravity and Dark Energy with Cosmology and Gravitational Waves

Date: November 06th 2019, 15h30

Speaker: Miguel Zumalacarregui (UC Berkeley & IPhT Saclay)

Title: Testing Gravity and Dark Energy with Cosmology and Gravitational Waves

Room: Cassini


Abstract

Alternative theories of gravity may provide viable models of cosmic acceleration with the possibility of alleviating shortcomings of the standard paradigm such as discrepant measurement of the Hubble parameter. I will present recent progress in constructing viable, yet extremely predictive theories of gravity and dark energy, extracting their cosmological implications and testing them with data, current and forthcoming. I will also present how most of these theories affect the propagation of gravitational waves. In particular, the speed of gravitational waves provides the most stringent test for a large class of theories, which have been recently ruled out by the GW speed measurement following the neutron star merger GW170817. Other effects on gravitational wave propagation (damping, modified dispersion and oscillations) can be used to test the landscape of gravitational theories.