Star formation and the evolution of massive galaxies across cosmic time
Publication Date
December 9, 2014
Creator
Abstract
This thesis investigates the evolution of massive galaxies throughout the last 11 billion years using measured stellar masses and star formation rates. Firstly, we present a study of the resolved star-forming properties of a sample of distant massive (M > 10{11} M) galaxies in the GOODS NICMOS Survey (GNS) within the redshift range 1.5 < z < 3 in order to measure the spatial location of ongoing star formation (SF). We find that the SFRs present in different regions of a galaxy reflect the already existent stellar mass density, i.e. high density regions have higher SFRs than lower density regions, on average. We find that these massive galaxies fall into three broad classifications of SF distributions. These different SF distributions increase the effective radii to z=0, by ~16 plus-minus 5 % , with little change in the Sersic index (n), with an average delta n = -0.9 plus-minus 0.9, after evolution. These results are not in agreement with the observed change in the effective radius and n between z ~2.5 and z ~0. We conclude that SF and stellar migration alone cannot account for the observed change in structural parameters for this galaxy population, implying that other mechanisms must additionally be at work to produce the evolution, such as merging.
In Chapter 2, we present a study of the stellar mass growth of the progenitors of local massive galaxies at number densities of n < or = 1x10{-4} Mpc{-3} in the redshift range 0.31.5 SF is the dominant form of stellar mass growth, while at z<1.5 mergers become the dominant form with minor mergers the dominant form of growth at z<1.0. We also explore the implication of these results on other galaxy formation processes such as the cold gas accretion rate of the progenitors of most massive galaxies over the same redshift range. We find that the gas accretion rate decreases with redshift with an average gas accretion rate of ~65 M yr{-1} over the redshift range of 1.51.7 and transitioning to high n objects at z<1.7. Splitting the high and low $n$ objects into SFing and passive samples. We find that 41 plus-minus 4 % of the sample at z>2.5 are passive low n systems, possibly implying that local massive galaxies were passive disk-like systems at early cosmic times.
In Chapter 2, we present a study of the stellar mass growth of the progenitors of local massive galaxies at number densities of n < or = 1x10{-4} Mpc{-3} in the redshift range 0.31.5 SF is the dominant form of stellar mass growth, while at z<1.5 mergers become the dominant form with minor mergers the dominant form of growth at z<1.0. We also explore the implication of these results on other galaxy formation processes such as the cold gas accretion rate of the progenitors of most massive galaxies over the same redshift range. We find that the gas accretion rate decreases with redshift with an average gas accretion rate of ~65 M yr{-1} over the redshift range of 1.51.7 and transitioning to high n objects at z<1.7. Splitting the high and low $n$ objects into SFing and passive samples. We find that 41 plus-minus 4 % of the sample at z>2.5 are passive low n systems, possibly implying that local massive galaxies were passive disk-like systems at early cosmic times.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
School of Physics and Astronomy
eprints ID
27762
UoN Repository URI
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