PhD ceremony: G. Sikkema, 13.15 uur, Academiegebouw, Broerstraat 5, Groningen
Thesis: The influence of the environment on the evolution of galaxies
Promotor(s): prof. R.F. Peletier, prof. E.A. Valentijn
Faculty: Mathematics and Natural Sciences
In this thesis, we explore how the properties of galaxies depend on environment where they reside. The thesis consists of two parts, with each having its own data-set.
Part 1 consists of observations done with a wide-field CCD-camera mounted on a middle-sized telescope. In Groningen, a software system ASTRO-WISE has been developed that will reduce observations the upcoming wide-field camera OmegaCAM. Our observations were used as a testbed for ASTRO-WISE. We looked at a region on the sky with a size of 16 full moons, which contains several galaxy clusters at a distance of about 1 billion lightyears. One type of galaxy, the so-called S0 galaxies, seem to have formed quite fast in the past few billion years in clusters. These type of galaxies probably evolve from spiral galaxies. Our observations give clues about how and where this transformation occurs. We find that the so-called red spirals might be a transition type of galaxy: between normal spirals and S0s. Furthermore, we find morphological differences between several types of galaxies in low and high density regions.
Part 2 consists of Hubble Space Telescope dataof six relatively nearby shell galaxies. Shell galaxies are elliptical galaxies which deviations (shells) in their light distribution. We have determined very precisely the colours and shapes of shells as well as the presence of dust in these galaxies. The results imply that shells are the remains of small dwarf galaxies that have merged with the much larger elliptical galaxy. We also looked if the shell galaxies contain recently formed globular clusters. We find that two out of six of our shell galaxies show evidence for young globular clusters.
In contrast to popular belief, lightning often does strike twice, but the reason why a lightning channel is ‘reused’ has remained a mystery. Now, an international research team led by the University of Groningen has used the LOFAR radio telescope to...
On March 29th professor of Applied Physics Jeff de Hosson was offered a farewell symposium, a few months after his official retirement date near the close of 2018. ‘But 29 March was the 100th birthday of Jan Francken, my predecessor.’ Besides, De Hosson...
Dozens of minor planets that used to orbit the Sun anonymously were named by the International Astronomical Union on 6 April 2019. The asteroid that used to be known as ‘minor planet 12655’ was named after Prof. Ben Feringa, winner of the 2016 Nobel...