The formation and evolution of galaxies is fundamentally driven by the formation of new stars out of cold gas.

Promotor: M. Franx, Co-Promotor: I.F. Labbé

An international team of astronomers that includes researchers from Leiden has discovered the most distant galaxy yet. The galaxy, called EGS8p7, is 13.23 billion light years away from Earth and already existed when the universe was only 550 million years old.

One of the key quests in astronomy is to study the growth and evolution of galaxies across cosmic time. Radio observations provide a powerful means of studying the formation of stars and subsequent buildup of distant galaxies, in a way that is unbiased by the presence of dust.

This thesis explores the theoretical and observational properties of distant massive galaxies that harbour active black holes in their centres and shine brightly at radio wavelengths.

Galaxies are environments where gas coalesces, cools, and is converted into stars. However, it remains unclear the exact mechanisms through which galaxies acquire, redistribute and lose their gas.

Promotor: H.J.A. Röttgering, Co-promotor: G.K. Miley

Labbe

Promotor: Prof.dr. K.H. Kuijken, Co-Promotor: Dr. H.Hoekstra

Promotor: Prof.dr. H.J.A. Rottgering, Co-promotor: David Sobral

Promotor: Koen Kuijken Co-promotor: Henk Hoekstra

This thesis investigates how galaxies form and what diversifies the evolutionary histories of galaxies.

The thesis deals with the study of giant radio galaxies (GRGs), which are radio galaxies of megaparsec sizes.

Promotores: Prof.dr. J. Schaye & Prof.dr. C. Steidel (California Institute of Technology)

Promotor: Prof.dr. M. Franx, Co-Promotor: Rychard Bouwens

Franx

This thesis focuses on the X-ray spectral analysis of merging galaxy clusters and the plasma code development for future high-resolution X-ray spectroscopy observations.

Galaxies form and evolve through close interaction with their surroundings. As a result, the heavy elements ('metals') that are synthesized in stars, are found both inside and outside galaxies.

When observing star-forming galaxies, we are not only seeing stellar light, but we also see how this interacts with galactic gas and dust. This thesis contains studies of the stellar, nebular and dust properties of low mass star-forming galaxies.

PhD Defence

Promotores: Prof.dr. M. Franx, Prof.dr. M. Kriek (Univ. of California at Berkeley)

Galaxies form and live inside dark matter haloes. As a consequence, they are exposed to the tidal fields generated by the surrounding matter distribution: this imprints a preferential direction to the galaxy shapes, which leads to a coherent alignment on physically close galaxies, called intrinsic a…

Promotores: Prof.dr. F.P. Israel, Prof.dr. P.P. van der Werf

In this thesis, the research focuses on the properties of dark matter and dark matter haloes and how they connect with the galaxies we can observe in the Universe.

Promotores: Prof.dr. J. Schaye, Prof.dr. S.D.M. White (MPA Garching)

Promotor: J. Schaye

Promotor: H.J.A. Röttgering, Co-promotor: M. Haverkorn

How did galaxies form? How did galaxies evolve?

Promotores: Prof.dr. M. Franx & Prof.dr. P.G. van Dokkum (Yale University)

Galaxy intrinsic alignments induce a major astrophysical contamination to weak gravitational lensing measurements and need to be modelled and mitigated when extracting cosmological information from such measurements.

We investigate the buildup of galaxies from various vantage points. The first two chapters focus on the stellar content of galaxies, especially the distribution of stellar masses at birth and potential variations therein in various galactic environments.

This thesis investigates the structural evolution and assembly of galaxies since the first few billions years after the big bang.

Promotor: F.P. Israel, Co-Promoter: R. Meijerink

Of all the mass in our Universe, 80% is thought to consist of a hypothetical and invisible substance called dark matter (DM).

In this thesis, I study the formation of large-scale structure and the physics of particle acceleration at large scales (~Mpc).

In 2015, Jorryt Matthee thought he discovered an extremely distant galaxy called CR7, which lacked elements heavier than helium. Three years later, he shows with measurements using the ALMA telescope that the galaxy does have carbon after all, and even in normal concentrations. The American Astronomical…

Researchers at Leiden Observatory study the fundamental physics that creates structure in the Universe. These processes collect matter into galaxies and gas into stars. With the use of powerful telescopes and advanced calculations and computer simulations, Leiden astronomers seek to understand the origin,…

Researchers at Leiden Observatory study the fundamental physics that creates structure in the Universe. These processes collect matter into galaxies and gas into stars. With the use of powerful telescopes and advanced calculations and computer simulations, Leiden astronomers seek to understand the origin,…

This thesis aims to enhance our understanding of galaxies by testing theoretical models of galaxy formation against observations, particularly in the cases of extreme systems which have been found to have an excess of baryonic mass in their central regions, in the form of either supermassive black holes…

In this thesis, I studied the origin and evolution of the non-thermal radiation in merging galaxy clusters.

Rossi

Promotor: Jelle S. Kaastra Co-promotor: Jelle de Plaa

Finally we know for sure that there is a black hole at the centre of our own galaxy. Today, astronomers unveiled the first ever photo of Sagittarius A*, a super-massive object at the centre of the Milky Way. This picture could only be taken thanks to the cooperation of telescopes worldwide.

Galaxies in the early universe are shrouded in a kind of mist: a cloud of hydrogen. With galaxies in the later universe this mist has disappeared. Astronomer Jorryt Matthee has made the first images of this dissipating mist. PhD defence 19 September.

With each discovery that is made, the universe reveals a fraction of its secrets: the most distant galaxies and quasars, the atmosphere of exoplanets, evidence of dark matter, complex molecules in space. This is what fills the days and nights of the researchers from the Leiden Observatory and their…

Using the MUSE instrument on ESO’s Very Large Telescope in Chile, an international team of scientists, including many Leiden astronomers, have conducted the deepest spectroscopic survey ever. They focused on the Hubble Ultra Deep Field, measuring distances and properties of 1600 very faint galaxies…

Stellar feedback is a crucial ingredient in the evolution of galaxies.

An international team of researchers led by Leiden University (the Netherlands) has mapped nine gigantic collisions of galaxy clusters. The collisions took place seven billion years ago and could be observed because they accelerate particles to high speeds. It is the first time that collisions of such…

After almost twenty years the record for the most distant radio galaxy has been broken. A team of astronomers led by Leiden PhD candidate Aayush Saxena has discovered a radio galaxy from the time when the universe was just one billion years old. The galaxy is at a distance of 12 billion light years…

An international team of astronomers, with researchers at Leiden Observatory playing a leading role, has mapped the fuel for galaxy formation in the iconic Hubble Ultra Deep Field. The results of the research have been accepted for publication in The Astrophysical Journal.