PhD Part A exam by Jens-Kristian Krogager – University of Copenhagen

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PhD Part A exam by Jens-Kristian Krogager

DARK's PhD Student, Jens- Kristian Krogager, will present his Part A PhD Exam Wednesday 30 October 2013 at 09:00 in 016 Rockefeller. Jens' supervisor is Johan Fynbo.

Title: "Characterizing Galaxy Evolution from Absorption and Emission"

Abstract: Damped Lyman- absorbers (DLAs), a class of QSO absorbers with neutral hydrogen column density NHI > 21020 cm^2, have taught us a lot about early galaxies since the rst sample was published 27 years ago. DLAs provide a powerful and precise method for studying the metallicities through cosmic time, and reveal detailed information about kinematics of the absorbing gas. However, for many years the physical nature of the galaxies, in which the absorption arises, has been mostly unknown, especially in terms of fundamental properties such as their sizes, masses, and dynamics. During the latest 3 years this situation has changed mainly thanks to near-IR spectrographs (X-shooter and SINFONI in particular). Here I present recent advances in detections of emission from high-metallicity DLAs thanks to high quality data from the Nordic Optical Telescope,b Hubble Space Telescope and the Very Large Telescope. Metal-rich DLAs appear to be associated with compact, star-forming galaxies and the damped absorption takes place at surprisingly large impact parameters relative to the half-light radii of the galaxies.

The second part of the thesis deals with the size evolution of evolved galaxies at high redshift. Massive galaxies are observed to be more compact at high redshift and the increase in sizes is usually ascribed to minor merging. However, we nd that merging may not be the main driver of size growth. Instead, we nd that the addition of larger galaxies quenched at later times drives the evolution of the population.