Found 36 talks width keyword large-scale structure

Thursday November 4, 2021

How well does galaxy clustering constrain cosmology?

Dr. Sergio Contreras

DIPC

Abstract

On the LCDM cosmology, dark matter collapses into virialised objects called haloes. The abundance and distribution of these haloes are a direct consequence of the cosmology of the Universe. By constraining the dark matter halo clustering, we could also constraint the cosmology from our Universe. Since dark matter haloes can not be observed, we need to use galaxies to trace them.

In this talk, I will present a new method that we develop capable of constraining cosmological information from the redshift space galaxy clustering. We use the scaling of cosmological simulations and the SubHalo Abundance Matching extended (SHAMe) empirical model to produce realistic galaxy clustering measurements over a wide range of cosmologies. We generate more than 500,000 clustering measurements at different cosmological and SHAMe parameters to build an emulator capable of reproducing the projected correlation function, monopole and quadrupole of the galaxies. We run an MCMC using this emulator to constrain the cosmology of the TNG300 hydrodynamic simulation. We correctly predicted the cosmology of the TNG300 simulation constraining sigma8 between [0.75,0.83] and Omega matter h^2 between [0.127,0.162]. The best constraints are obtained when including scales below 2 Mpc/h and when combining all different clustering statistics. We conclude that our approach can be used to constrain cosmological and galaxy formation parameters from the galaxy clustering of galaxy surveys.

Archived in: Cosmology - Keywords:SDSS, Big data, cold dark matter, dark energy, dark matter, large-scale structure, redshift, gravitation, radial velocities

Abstract

Tuesday May 25, 2021

The Cosmic NeuTRIVIA game

Drs. Olga Mena

IFIC

Abstract

In this talk, we shall review the impact of the neutrino properties on the different cosmological observables. We shall also present the latest cosmological constraints on the neutrino masses and on the effective number of relativistic species. Special attention would be devoted to the role of neutrinos in solving the present cosmological tensions.

Archived in: Cosmology - Keywords:Planck, scattering, particle physics, nucleosynthesis, neutrinos, gravitational lensing, abundances, Microwave emission, large-scale structure, early universe, distance scale, dark energy, CMB, Data mining, SDSS

Abstract

Thursday May 13, 2021

Constraints on Ultra-Light Dark Matter from Galactic Rotation Curves

Prof. Diego Blas

Imperial College

Abstract

Bosonic ultra-light dark matter (ULDM) in the mass range m ~ $10^{-22} - 10^{-21} \rm eV$ has been invoked as a motivated candidate with new input for the small-scale `puzzles' of cold dark matter. Numerical simulations show that these models form cored density distributions at the center of galaxies ('solitons'). These works also found an empirical scaling relation between the mass of the large-scale host halo and the mass of the central soliton. We show that this relation predicts that the peak circular velocity of the outskirts of the galaxy should approximately repeat itself in the central region. Contrasting this prediction to the measured rotation curves of well-resolved near-by galaxies, we show that ULDM in the mass range m ~ $10^{-22} - 10^{-21} \rm eV$ is in tension with the data.

Archived in: Cosmology - Keywords:cold dark matter, dark matter, large-scale structure, galactic formation, galactic halos, rotation curve, fundamental physics, gravitation, radial velocities, Galactic center, Galactic halo, Galactic structure

Abstract

Thursday April 29, 2021

What causes the accelerated expansion of the Universe?

Prof. Steen Hansen

COpenhagenUNi / DARK cosmology center

Abstract

The expansion of the Universe is in an accelerated phase. This
acceleration was first estabilished by observations of SuperNovae, and
has since been confirmed through a range of independent observations.

The physical cause of this acceleration is coined Dark Energy, and
most observations indicate that Einsteins cosmological constant
provides a very good fit. In that case, approximately 70% of the
energy of the Universe presently consists of this cosmological
constant.

I will in this talk address the possibility that there may exist other
possible causes of the observed acceleration. In particular will I
discuss a concrete model, inspired by the well-known Lorentz force in
electromagnetism, where Dark Matter causes the acceleration. With a
fairly simple numerical simulation we find that the model appears
consistent with all observations.

In such a model, where Dark Matter properties causes the acceleration
of the Universe, there is no need for a cosmological constant.