Master's thesis defense by Thøger Juul Thorsen – University of Copenhagen

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Master's thesis defense by Thøger Juul Thorsen

Thøger Juul Thorsen will defend his Master's thesis Monday 4 April at 10:00 in Auditorium D at Blegdamsvej. 

Title: Probing Early Galaxy Formation With Damped Lyman alpha-absorbers

The overall goal of this project has been to contribute to our understanding of the
nature of the first galaxies through the study of a Damped Lyman a Absorber.
DLAs are clouds with a high column density of neutral hydrogen, leaving a characteristically
strong and broad absorption line in the spectrum of a background
light source, in this case a quasar.
The study of the DLA absorption features in the spectra of quasars is a powerful
tool for probing early history of galaxy formation, as it allows us to extract
detailed information about chemical composition and kinematical properties in
the gas of very distant and/or faint galaxies. The information gained from the
DLA can help understand the processes by which the large scale structure of the
Universe has evolved from minute temperature fluctuations in the Cosmic Microwave
Background to the galaxies, clusters and enormous voids of the local
Universe; and hence understand the nature of the Dark Matter, the gravitational
influence of which is governing this evolution. Furthermore, it can help understand
how the early clouds of hydrogen and helium have since been chemically
enriched with the elements that today make up our planet and a major part of
The data studied here are produced by a group led by Johan Fynbo in an attempt
to find weak lines of emission from the galaxies hosting the DLA clouds.
The data investigated consist of three exposures of a quasar of redshift z ≈
3.07, taken with the X-Shooter spectrograph at the ESO Very Large Telescope
in Paranal, Chile. In these spectra were found two DLA systems with redshifts
z ≈ 2.58 and z ≈ 2.412, respectively, of which the latter was the subject for this
The system was found to be a relatively hydrogen rich DLA with a metal
abundance and evidence of dust. It shows a dynamical structure consistent with
the assumption that DLA systems are young galaxies with active star formation,
and that the more massive systems have the higher star formation rate and correspondingly
higher abundances of metals.