Cosmology with lyman-break galaxies
File(s)
Author(s)
Petri, Francesco
Type
Thesis or dissertation
Abstract
This document will outline a series of projects and relevant background material for exploiting Lyman-break galaxies (LBGs) for cosmological parameter inference. A significant number of LBGs with redshifts 3 < z < 5 are expected to be observed by the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). This will enable us to probe the universe at higher redshifts than is currently possible with galaxy clustering and weak lensing surveys. However, accurate inference of cosmological parameters requires precise knowledge of the redshift distributions of selected galaxies, where the number of faint objects expected from LSST alone will make spectroscopic based methods of determining these distributions extremely challenging. To overcome this difficulty, it may be possible to leverage the information in the large volume of photometric data alone to precisely infer these distributions. In this work we use stellar population synthesis (SPS), to estimate uncertainties on LBG redshift distributions for LSST. We characterise some of the modelling uncertainties inherent to SPS by introducing a flexible parameterisation of the galaxy population prior, informed by observations of the galaxy stellar mass function (GSMF) and cosmic star formation density (CSFRD). We will present a forward model for LBG redshift distributions and their uncertainties, which we can use to predict the number densities and contamination present in LBGs selected by LSST. The development of this model allows us to provide a forecast on cosmological parameters purely from photometry. We marginalise over the space of redshift distributions and propagate this to constraints on cosmological parameters in a Fisher forecast. Assuming a known dust attenuation model, we forecast constraints on the 8 parameter comparable to Planck cosmic microwave background (CMB) constraints, at the 1-2% level. This adds further realism compared to previous forecasts and further motivates the use of LBGs for cosmology.
Version
Open Access
Date Issued
2025-09-29
Date Awarded
2026-06-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Leistedt, Boris
Mortlock, Daniel
Sponsor
Science and Technology Facilities Council (Great Britain)
Grant Number
N/A
Publisher Department
Department of Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)