School of Physics - Theses

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Type: PhD thesis × Subject: astrophysics × Author: Carrasco Nunez, Daniela Patricia ×

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    Simulations of source recovery and completeness in galaxy surveys at high redshift
    Carrasco Nunez, Daniela Patricia ( 2018)
    The search for and characterisation of galaxies at high-redshift is a very active topic in Astrophysics. Thanks to advances in observations from space, the redshift frontier is approaching the epoch of formation of first generation objects. Thus, these samples of galaxies can give us insight into the processes that govern galaxy formation and evolution. One of the key observables used to characterise galaxy populations throughout the cosmic history is their luminosity function (number of galaxies per unit luminosity per unit volume), which requires knowledge and characterisation of the completeness and selection functions of a survey, in addition to the catalogue of discovered objects. In this thesis, we present a search for high-redshift galaxies (redshift z > 6) in two in the Hubble Space Telescope surveys, the Brightest of Reionizing Galaxies Survey (BoRG), and the Reionization Lensing Cluster Survey (RELICS) using a photometric selection technique (the Lyman break dropout selection). We aim at using the resulting galaxy candidates to estimate a new measurement of the luminosity function at z ~ 10. To achieve that, we develop GLACiAR, an open Python-based tool available on GitHub, which is designed to estimate the completeness and selection functions in galaxy surveys. The code is tailored for multiband imaging datasets aimed at searching for high-redshift galaxies through the Lyman Break technique, but it can be applied broadly. The code generates artificial galaxies that follow Sérsic profiles with different indexes and with customisable size, redshift and spectral energy distribution properties, adds them to input images, and measures the recovery rate. We finally apply GLACiAR to quantify the completeness and redshift selection functions for J-dropouts sources (redshift z ~ 10 galaxies). Our comparison with a previous completeness analysis on the same dataset shows overall agreement, but also highlights how different modelling assumptions for artificial sources can impact completeness estimates.