In this thesis we push the boundaries of high-resolution imaging at radio frequencies between 100 and 200 MHz. Using the International LOFAR Telescope that spans across Europe we achieve sub-arcsecond angular resolution.

Promotor: Prof.dr. H. J. A. Röttgering, Co-Promotor: Dr. M. Haverkorn

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

By a stroke of luck, a team led by Dutch PhD student Martijn Oei has discovered a radio galaxy of at least 16 million lightyears long. The pair of plasma plumes is the largest structure made by a galaxy known thus far. The finding disproves some long-kept hypotheses about the growth of radio galaxie…

The Low Frequency Array enables studies of low-frequency carbon radio recombination lines with unprecedented sensitivity, spectral and spatial resolution.

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,…

Low-mass main-sequence stars like our Sun are continuous sources of outflowing hot magnetised plasma. In the case of the Sun, this is known as the solar wind, whereas for other stars they are called stellar winds.

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…

Rossi

A Dutch-Italian-German team of astronomers has observed a huge glow of radio emission around a cluster of thousands of galaxies. They combined data from thousands of LOFAR antennas that were focused for 18 nights on an area the size of four full moons. This is the first time astronomers have been able…

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

A galaxy is already incredibly large, but it can get even bigger. Astronomer Reinout van Weeren investigates clusters of galaxies, one of the largest structures in the universe. For his research into the origins and evolution of these clusters, he obtained an ERC Starting Grant of 1.5 million euros.…

Pulsars were first discovered in 1967 and since then the population has grown and expanded over several wavelengths.

The origin and evolution of galaxies are closely tied to the cyclic feedback processes between stars and the interstellar medium (ISM).

An international team of astronomers has published the most sensitive images of the Universe ever taken at low radio frequencies, using the International Low Frequency Array (LOFAR). ‘LOFAR is unique in its ability to make high-quality images of the sky at metre-wavelengths’, said Huub Röttgering, Leiden…

Through the clever use of two types of telescopes, a team of researchers has produced stunning images of clusters of galaxies. This not only produces beautiful images, but also provides more information about the enormous amounts of energy released around supermassive black holes in clusters. The astronomers,…

For the first time, astronomers have observed in three dimensions that gas from spiral galaxies is blown upwards and downwards at high speed, far out of the galaxy. They thereby confirm the theory of galaxy evolution: that star-forming galaxies create intergalactic gas flows by discharging gas along…

Galaxies are often found in clusters, which contain many “red and dead” members that stopped forming stars in the distant past. Now, an international team of astronomers, led by Andra Stroe of Leiden Observatory and David Sobral of Leiden and the University of Lisbon, has discovered that these comatose…

In this thesis, we use low-frequency and high-frequency radio observations to address the following questions regarding quasars: is the radio loud/quiet quasar dichotomy real?

This paper critically compares seven widely used risk assessment tools for violent extremism, including the VERA-2R, the ERG 22+, the SQAT, the IR46, the RRAP, the Radar, and the VAF.

In this thesis, we present new laboratory data of interstellar dust analogues.

The intracluster medium (ICM) is a hot, tenuous and X-ray emitting gas that pervades galaxy clusters.

The radio sky harbours both galactic and extragalactic sources of arcminute- to degree-scale emission of various physical origins. To discover extragalactic diffuse emission in the Cosmic Web beyond galaxy clusters, one must image low–surface brightness structures amidst a sea of brighter compact fore-…

How do galaxies form? That is what astronomer Mariska Kriek will be researching in the coming years. She received an NWO Vici grant of 1.5 million euros to study galaxies in the early universe. ‘This research uses new and unprecedented observations from the James Webb Space Telescope (JWST). These allow…

Hot astrophysical plasma is ubiquitous in the Universe, from comets in our Solar system to the largest scale structures -- the cosmic web filaments. These hot plasmas, with the temperature of a few millions of degrees, are often observed in the X-ray wavelength range.

Dark matter is one of the biggest mysteries of the Universe. Its properties cannot be explained with the known laws of physics and elementary particles.

When galaxies collide, do the black holes at their centre form a supersized black hole? This is what we think happens, but it's not as simple as that, according to Simon Portegies Zwart. Zwart, computer scientist and astronomer, has been awarded a VICI grant to research this phenomenon.

This thesis presents pioneering work on the panchromatic emission of some of the most luminous galaxies in the early Universe: star forming galaxies and active galactic nuclei.

An overview of awards and prizes granted to our staff and students in 2019, as well as special appointments and royal distinctions.

Galaxies in the Universe are distributed along the intricate framework of the Cosmic Web. Groups and clusters of galaxies comprise the densest regions in this network, and therefore, are excellent cosmic laboratories to study different aspects of galaxy evolution in extreme environments.

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…

An overview of awards and prizes granted to our staff and students in 2022, as well as special appointments at Leiden University and other institutions.

An international team of more than 200 astronomers from 18 countries has published hundreds of thousands of unknown galaxies. The data are part of a project lead by Leiden professor of Observational cosmology Huub Röttgering. Both Dutch and international media reported extensively about the publica…

The success of Dutch radio astronomy in the last century was largely due to Leiden astronomer Jan Hendrik Oort. He made astute use of circumstances in the post-war period. Historian Astrid Elbers' research focuses on this golden period.

An overview of awards and prizes granted to our staff and students in 2018, as well as special appointments and royal distinctions.

Media all around the world reported about it: the most detailed images yet seen of galaxies, shot by radio telescope LOFAR. The international team behind these amazing results were led by Leah Morabito at Durham University and included three talented Leiden astronomers.

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…

Ineke van der Ham gives a radio interview at Radio 1.

A team of Leiden astronomers used the latest set of data from ESA’s Gaia mission to look for high-velocity stars being kicked out of the Milky Way, but were surprised to find stars instead sprinting inwards – perhaps from another galaxy.

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…

Promotor: Prof.dr. A.G.G.M. Tielens, Co-Promotor: J.B.R. Oonk

Astronomers led by Pieter van Dokkum have discovered a galaxy that barely contains any dark matter, which actually proves that dark matter does indeed exist. The research results will be published this week in Nature.

An Active Galactic Nucleus (AGN) is a highly luminous region at the center of a galaxy, powered by the accretion into a supermassive black hole and emitting energy from radio waves to gamma rays, often outshining the host galaxy.

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.

An international team of astronomers, including Leiden's Maciej Bilicki, has discovered an enormous supercluster of galaxies. The supercluster had previously been overlooked because it was obscured by our own Milky Way. The researchers are publishing their findings in the Monthly Notices of the Royal…

Dark matter represents around eighty per cent of the total mass in the Universe. Yet, we still don't really know what it's made of. Astronomer Pavel Mancera Piña is looking for answers. With a Veni grant from NWO and the most advanced telescopes, such as the James Webb Space Telescope, he will investigate…

The largest galaxies in the Universe feed off cosmic oceans, which helps them grow. This is the presumption of an international team of scientist with two Leiden astronomers, based on observations of the ‘Spiderweb’ galaxy. The researchers published their evidence in Science on 2 December 2016.

On this page you will find an overview of awards and prizes granted to our staff and students in 2023, as well as special appointments at Leiden University and other institutions.