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Durham e-Theses
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Resolved Studies of the Dynamics, Star
Formation and Chemical Properties of
High-Redshift Galaxies

GILLMAN, STEVEN,RICHARD (2020) Resolved Studies of the Dynamics, Star
Formation and Chemical Properties of
High-Redshift Galaxies.
Doctoral thesis, Durham University.

PDF - Accepted Version


Understanding the physical mechanisms that drive the evolution of galaxies
through cosmic time is one of the fundamental pillars of modern-day observational
astronomy. Developing a robust theory of galaxy formation enables us to address vital
questions connected to the structural and dynamical evolution of galaxies, Why are the
kinematic and morphological properties of high-redshift galaxies much more turbulent
and irregular than those we see in the local Universe? What drives the galaxies towards
the well-ordered, stable systems which ultimately lead to the emergence of the Hubble
Sequence? To answer these questions, we must first empirically constrain the fundamental
properties (e.g. mass, energy, and angular momentum) of galaxies across cosmic time.
This thesis presents an analysis of the dynamics and morphologies of star-forming
galaxies from z = 0.8 to z = 3.5. We include both seeing-limited near-infrared integral field
spectroscopy observations from the K-band Multi Object Spectrograph (KMOS) as well
as adaptive optics integral field observations from the Gemini Northern Integral Field
Spectrograph (Gemini-NIFS), the Spectrograph for INtegral Field Observations in the
Near Infrared (SINFONI) and the OH-Suppressing Infrared Integral Field Spectrograph

We first analyse the connection between a galaxy’s dynamics and its rest-frame optical
morphology by exploiting seeing-limited KMOS observations from the KMOS Galaxy
Evolution Survey (KGES) that probe the Hα and [Nii] emission lines in 288 star-forming
galaxies at z ∼ 1.5. We combine the integral field data with high-resolution CANDELS
HST near-infrared imaging to constrain the morphology of the galaxies in the sample. We
identify that low-mass, compact galaxies have lower specific angular momentum whilst
more massive disc galaxies have higher angular momentum. At fixed mass, peculiar
galaxies have similar levels of angular momentum to that of disc galaxies whilst having
higher star formation rate surface densities. We propose that the peculiar morphologies
are driven by higher gas fractions leading to a more clumpy interstellar medium.

We then explore the chemical abundance properties of ∼700 high-redshift star-forming
galaxies that make up the KGES and KROSS surveys. Using the [Nii] / Hα emission line
ratio we analyse the connection between gas-phase metallicity, stellar mass and fundamental
galaxy properties. We establish that peculiar galaxies have a lower metallicity for a given
stellar mass compared to disc and spheroidal systems, which we attribute to their higher
gas fractions. The metallicity gradients of the galaxies correlate negatively with stellar
mass and positively with specific star formation rate. This agrees with the inside-out
model of galaxy formation whereby galaxies first form stars at their centres, enriching the
surrounding interstellar medium. On average, we identify flat metallicity gradients which
we demonstrate agrees with other studies of high-redshift galaxies and numerical models
in which feedback processes are important.

Finally, we use high-resolution adaptive optics observations to map out the Hα, [Nii] and
[Oiii] nebula emission lines in 34 star-forming galaxies from z = 0.8 to z = 3.5. We explore
the evolution of the normalisation of the specific angular momentum – stellar mass plane
across ∼ 5Gyr, and constrain the internal distribution of specific angular momentum in
each galaxy. We establish that the specific angular momentum becomes less centrally
concentrated in galaxies with higher stellar mass due to a combination of stellar feedback
and gas accretion. This leads to an evolution in the morphologies of the galaxies towards
more a late-type dominated population.

Item Type:Thesis (Doctoral)
Award:Doctor of Philosophy
Faculty and Department:Faculty of Science > Physics, Department of
Thesis Date:2020
Copyright:Copyright of this thesis is held by the author
Deposited On:08 Jun 2020 11:10

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