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Galaxy Formation in the Lambda-Cold Dark Matter Cosmology



In this thesis I explore the effects of the various physical processes behind\ud galaxy formation and evolution in hierarchical cosmologies by using\ud semi-analytical modelling. I use the Durham semi-analytical model GALFORM.\ud I first test the GALFORM model predictions\ud using observations from the Sloan Digital Sky Survey (SDSS). I use two\ud different variants of the model, Baugh et al (2005), which assumes a top-heavy\ud initial mass function (IMF) in starbursts and superwind feedback, and Bower et\ud al (2006), which incorporates AGN feedback with a standard IMF. I compare the\ud luminosity function, colours, sizes and morphology distributions of present-day\ud galaxies in the models and with the SDSS. The Bower et al model\ud better reproduces the shape of the luminosity function, the\ud morphology-luminosity relation and the colour bimodality observed in the SDSS\ud data. The Baugh et al model is much more successful at predicting\ud galaxy sizes for late-type galaxies. Both models have problems with\ud the sizes of early-type galaxies, which are predicted to be too large\ud for low luminosities and too small for high luminosities compared to SDSS. I\ud tested the impact on the model predictions of varying the prescriptions for\ud supernova feedback, disk instabilities and galaxy mergers.\ud In the second part of the thesis I explore the connection between two high\ud redshift star-forming galaxy populations and present-day galaxies and\ud their contribution to the star formation history. I built galaxy merger trees\ud and followed the evolution and properties of submillimetre galaxies (SMGs) and\ud Lyman-break galaxies (LBGs) using the Baugh et al (2005) model.\ud The model predicts that the descendants of SMGs (S_{nu} > 5 mJy) have a median stellar mass of ~10e11/h solar masses, and that\ud more than 70% of these descendants are bulge-dominated.\ud More than 50% of present-day galaxies with stellar masses larger\ud than 7 x 10e11/h solar masses are predicted to be descendants of such\ud SMGs. Somewhat controversially, the stellar mass produced in the\ud submillimetre phase contributes only 0.2% of the total present-day\ud stellar mass, and 2% of the stellar mass of SMG descendants. The descendants of\ud z=3 LBGs are predicted to have a median stellar\ud mass equal to that of the Milky Way (M = 4 x 10e10/h solar masses), while the descendants of z=6 LBGs\ud are predicted to have a larger median stellar mass (M = 10e11/h solar masses). The model predicts that only one in every 16 and one in\ud every 50 Milky Way mass galaxies have a Lyman-break galaxy progenitor at z=3\ud and z=6 respectively.\u

Topics: methods: numerical, galaxies: evolution, galaxies: formation
Year: 2010
OAI identifier:
Provided by: Durham e-Theses

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