Roy, Nivya (2017) Formation and Evolution of Galaxies and the Search for Strong Lenses within Kilo Degree Survey. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Lingua: English
Title: Formation and Evolution of Galaxies and the Search for Strong Lenses within Kilo Degree Survey
Date: 7 April 2017
Number of Pages: 163
Institution: Università degli Studi di Napoli Federico II
Department: Fisica
Dottorato: Fisica fondamentale ed applicata
Ciclo di dottorato: 28
Coordinatore del Corso di dottorato:
Napolitano, Nicola RUNSPECIFIED
LaBarbera, FrancescoUNSPECIFIED
Date: 7 April 2017
Number of Pages: 163
Uncontrolled Keywords: Galaxy, Structural parameters, Size evolution, Compact galaxies, Strong Lensing
Settori scientifico-disciplinari del MIUR: Area 02 - Scienze fisiche > FIS/05 - Astronomia e astrofisica
Date Deposited: 03 May 2017 15:19
Last Modified: 14 Mar 2018 13:24
DOI: 10.6093/UNINA/FEDOA/11595


We have obtained structural parameters of about 340,000 galaxies from the Kilo Degree Survey (KiDS) in 153 square degrees of data release 1 and 2. We have performed a seeing convolved 2D single Sersic fit to the galaxy images in the 4 photometric bands (u; g; r; i) observed by KiDS, by selecting high signal-to-noise ratio (S/N> 50) systems in every bands. The 90% completeness reached in different bands are 18.2 in u, 20.2 in g, 20.2 in r, and 18.5 in i-band. We have classified galaxies in passive spheroids and disc-dominated by combining their spectral energy distribution properties and their Sersic index. Uncertainties on derived parameters (effective radius, Sersic index, central surface brightness, total magnitude, ellipticity, position angle etc.) and the presence of systematics in their estimates have been evaluated using mock galaxy images and by direct comparison with literature estimates on common systems. Using the photometric redshift derived from machine learning techniques, we have then derived the evolution of the main structural parameter of the galaxy sample (e.g. size and mass) versus redshift, for both mass complete sample of passive spheroids and disc-dominated galaxies up to redshift 0.6 and compared that with other datasets and against predictions of hydro-dynamical simulations. Overall results show a significant evolution of the galaxy structural quantities at intermediate redshift for the massive systems (log M/M⊙ > 11, Chabrier IMF) , while there seems to be almost no evolution for less massive galaxies (log M/M⊙ < 11). These results, based on 1/10 of the expected KiDS area, reinforce precedent results based on smaller statistical samples and are expected to be consolidated with the data coming from the next survey releases. We have identified a peculiar class of galaxies, the so-called ultra-compact massive galaxies, which are rare systems having effective radius <1.5kpc and log M/M⊙ > 11. In the 156 square degrees of KiDS DR1 and 2 we found 92 compact systems and studied the evolution of their density distribution with redshift. Finally, in the classification of the features found in the residual images, we have identified faint arc-like structures from strong galaxy-galaxy lensing events. We have then started a spin{off project aimed at searching Strong Lensing (SL)features around KiDS galaxies.


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