Fast radio bursts (FRBs) are so crazily bright that they must be powered by uniquely energetic emission mechanisms. Identifying their physical nature requires good localisation of more detections, and broadband studies enabled by real-time telescope combinations. I will present the results from the Apertif FRB survey (ALERT) that ran 2019-2022. ALERT performed wide-field, fully coherent,...
Fast radio bursts (FRBs) are extragalactic radio transients of microsecond to millisecond duration, whose physical origin is largely unknown. Some FRBs are known to repeat, which rules out cataclysmic progenitor models for these sources. Repeating FRBs exhibit significantly different temporal widths and bandwidths as compared to the non-repeating sources. A potential explanation for these...
The mergers of two neutron stars are exceptional multi-messenger events including short gamma-ray burst (GRB), gravitational wave and kilonova/afterglow emission. These events enable us to probe fundamental physics in one of the most extreme environments in the Universe. A key outstanding question is the remnant’s nature: with its expected mass and rapid spin, it could either be a black hole...
Fast radio bursts (FRBs) are enigmatic millisecond-duration radio flashes with an extragalactic origin. FRBs sources can be divided into two populations: repeating and apparently non-repeating sources. The burst energy distribution from repeating FRB sources is an important diagnostic tool that can be used to better understand the emission process, cosmological applications, and the potential...
The current climate crisis has led to UN and EU regulations to reduce greenhouse gas emissions by 55% in 2030. Astronomers should lead this effort by example, as they are aware of the lack of a Planet B to live on.
In the Netherlands, the RvdA installed a working group to monitor and improve the sustainability of Dutch astronomy, including outreach & communication on this topic. Our kickoff...
As the intracluster medium (ICM) in galaxy clusters cools through the emission of X-ray radiation, it sinks down toward the central galaxy where it fuels the AGN. This AGN subsequently emits radio-mode feedback in the form of powerful jets of relativistic plasma which re-energize the ICM, completing the feedback cycle. Measurements of the energy injected by radio-mode feedback into the cluster...
Neutral particles play a crucial role in understanding the origin of ultra-high energy cosmic rays. Neutrinos keep the directional information as they are not deviated by the magnetic fields and would point back to the sources. In the 1.0 EeV energy range, neutrinos are expected to be produced in the same sources where cosmic rays are thought to be accelerated. The Radio Detector of the Pierre...
Most stars form in stellar clusters that dissolve into the galactic field on timescales of tens to hundreds of millions of years. Planet formation takes place in a protoplanetary disk around young stars, disks that have typical lifetimes of a few millions years. The process of planet formation thus typically takes place in a stellar cluster environment. Understanding the impact of this...
Active Galactic Nuclei (AGN) are intrinsically variable sources. The observed variability in the optical can be explained as the sum of the reprocessing of very fast variations in the far UV or X-rays, and intrinsic variability from the accretion disk. Considering only reprocessing, which most likely corresponds to the fastest varying component, we can associate the shortest timescale of...
A key question in stellar astronomy is whether there are habitable planets around stars other than our Sun. An important factor in determining this is stellar activity, as stellar eruptions have direct impact on the atmosphere of an exoplanet. Radio emission, especially with a high degree of circular polarization, can provide a direct measurement of the magnetic field and the plasma properties...
AT2018cow is a well studied fast blue optical transient. Dispite a plethora of data, there is no consensus on the nature of the event. We use HST data between two and four years after the event to investigate the environment of this transient. Surprisingly there is still transient emission detected at the location of AT2018cow in this time period. This late time emission resembles emission...
JWST's science operations began in July 2022 after a successful launch and six months of commissioning. NOVA played a major role in the development of the Mid-Infrared Instrument (MIRI), in particular in its Medium Resolution Spectrometer (MRS). MIRI is the only instrument that covers wavelengths beyond 5 microns and is used to investigate a wide variety of objects, from galaxies to star...
In the last few years, the NICER collaboration has provided mass and radius inferences, via pulse profile modeling, for two pulsars: PSR J0030+0451 and PSR J0740+6620. Given the importance of these results for constraining the equation of state of dense nuclear matter, it is crucial to validate them and test their robustness. We therefore explore the reliability of these results and their...
The infrared signals of polycyclic aromatic hydrocarbons (PAHs) have been detected in numerous circumstellar discs. PAHs contribute to the heating of the disc's photosphere through efficient UV absorption and are crucial for disc evaporation models. Despite a correlation between effective stellar temperature and low PAH detection rates, the diversity of PAH detections at similar stellar...
Fast Radio Bursts are millisecond duration, extragalactic, coherent flashes of radio emission. Some repeating fast radio bursts are exceptionally more active than others. FRB 20220912A was discovered in the last quarter of 2022 as it entered an intense active period. During this time, we detected many bursts as part of our repeating FRB monitoring campaign on the Nançay Radio Telescope, ECLAT...
There is growing consensus that the formation of high-mass stars proceeds through disk accretion, similar to that of lower mass stars. To this end, we have undertaken a large observational program (CORE) making use of interferometric observations from the NOrthern Extended Millimetre Array (NOEMA) for a sample of 20 high-mass protostellar objects in the 1.3 millimetre wavelength regime...
The majority of massive stars are born in binaries, and most unbind upon the first supernova. With the precise proper motion measurements of Gaia, it is possible to trace back the trajectory of stars in the vicinity of young supernova remnants and neutron stars to search for intersecting paths, and hence ejected companions. At present, only a handful of supernova runaway candidates are known,...
A fraction of the nearby M dwarfs have detectable radio emission, which can be driven by several emission mechanisms. By observing the polarization, position and temporal behavior of this emission, we want to characterize it, and understand what mechanism is active in these radio stars.
We make use of the high astrometric accuracy and sensitivity available through the European VLBI Network....
Today, ALMA and JWST are revolutionizing our views of star & planet formation and galaxy evolution with their unprecedented sensitivity and resolution at submillimeter and near/mid-IR wavelengths.
However, many outstanding questions in these areas can only be answered with observations in the far-infrared domain, which generally need space-based instrumentation.
For planet formation, these...
The flaring events observed in the Sagittarius A* supermassive black hole system can be attributed to the nonhomogeneous nature of the near-horizon accretion flow. Bright regions in this flow may be associated with density or temperature anisotropies, corresponding to so-called "bright spots" or "hot spots." Such orbiting features may explain observations at infrared wavelengths, as well as...
The vast majority of extragalactic, compact continuum radio sources are associated with star formation or jets from (super)massive black holes and, as such, are more likely to be found in association with starburst galaxies or early type galaxies. Recently, two new populations of radio sources have been identified: (a) compact and persistent sources (PRS) associated with fast radio bursts...
Young massive clusters provide an ideal place to study the outcome of the star-formation process and the early dynamics of star clusters. With Gaia (E)DR3, we have studied the young massive clusters NGC 6611 in the Eagle Nebula (M16) and NGC 6618 in the Omega Nebula (M17). We determine membership and age of the cluster and search for stars that may have originated in the cluster. For NGC 6611,...
At the end of the 18th century, amateur astronomer Eise Eisinga built the largest planetarium the world had ever seen. He placed it on the ceiling of the living room of his house in Franeker, in the northern part of the Netherlands. The project took him seven years of designing, building and constructing. By the time it was nearly finished, the news about the planetarium was widespread. He...
We are working on is a work climate survey of Dutch astronomy, under the direction of the NWO tafel voor astronomie and would like to update the community on this and other activities.
WEAVE is the next-generation wide-field survey facility for the William Herschel Telescope (WHT). WEAVE will provide the instrument required for full scientific exploitation of the Gaia, LOFAR, and APERTIF surveys in the Northern Hemisphere. WEAVE is a multi-object and multi-integral-field-unit (IFU) facility utilizing a large, new 2-degree-diameter prime focus corrector at the WHT with a...
The recommendations from the most recent Decadal Survey on Astronomy and Astrophysics include a NASA-led probe-class X-ray telescope to be launched in the 2030s. I will discuss the mission concepts that are being developed as a response, with particular focus on SRON’s contribution to the observatories that will address the priority area “Unveiling the Drivers of Galaxy Growth”. Galaxy...
Mid-infrared observations are potentially powerful in identifying heavily obscured AGNs which have weak emission in other wavelengths. MIRI onboard JWST offers an excellent chance to perform such studies. We take advantage of the MIRI imaging data from the CEERS survey to investigate the AGN population in the distant universe. We estimate the source properties of MIRI-selected objects...
Thanks to integral field unit (IFU) spectroscopy, spatially-resolved metallicities have been measured in thousands of galaxies. This has built up a census of the baryonic cycle in local galaxies, which is crucial to understand how processes local to the interstellar medium (ISM) contribute to global trends in galaxies and influence the dynamics of the circumgalactic medium (CGM). JWST has...
Merging galaxy clusters often host an impressive collection of diffuse radio sources. These diffuse synchrotron sources can be explained by a non-thermal pool of relativistic electrons accelerated by shocks and turbulence in the intracluster medium. The origin of the pool of relativistic electrons and details of the acceleration mechanisms in clusters are still open questions. Due to the often...
Cosmic reionisation is one of the last major milestones in the global evolution of the Universe: by z~6, the hydrogen in the intergalactic medium becomes fully ionised by the radiation produced predominantly by massive stars in star-forming galaxies. Because of the increasing opacity of the IGM, completing the census of these ionising sources is still a major challenge on both the...
Galaxy mergers are one of the most violent processes and play a crucial role in galaxy evolution. However, the relative importance of mergers in mass growth and evolutionary events like AGN activity is not understood in detail. One of the main reasons is that mergers are difficult to identify with traditional methods and, in addition to being rare events, lead to incomplete and unreliable...
We use FLAMINGO, the biggest full hydro cosmological simulation ever, to study the most massive objects in the universe and do a direct comparison with observations. FLAMINGO hosts many thousands of massive clusters, in their full cosmological environment, making it an ideal testing ground to do a statistically relevant comparison with observations. Using a new forward modelling pipeline,...
Our Galactic halo hosts some of the most metal-poor stars. These are relics from the era of the smallest, earliest galaxies that merged into the Milky Way.
However, finding many of these extremely metal-poor (EMP) stars is challenging because they are rare among the more metal-rich populations in the Galaxy. The staggering Gaia DR3 provides low-resolution spectrophotometry for about 220...
Despite its crucial role in shaping our understanding of galaxy formation and evolution, the low mass end of the high redshift galaxy mass function has so far remained largely unknown. This is specially true for the high redshift universe, where even the deepest surveys have been unable to probe this elusive galaxy population.
To address this challenge, we leverage the powerful...
Galaxy formation in the first billion years mark a time of great upheaval in our cosmic history: the first sources of light in the Universe, these galaxies ended the 'cosmic dark ages' and produced the first photons that could break apart the hydrogen atoms suffusing all of space starting the process of cosmic reionization. At the forefront of astronomical research, the past few years have...
Various feedback mechanisms, such as star formation, large-scale outflows, shocks or Active Galactic Nuclei, affect the shape and evolution of galaxies. Starburst galaxies, in particular, show exceptionally higher star-formation rates compared to regular galaxies (e.g. the Milky Way), indicating different physical conditions. Understanding how these physical conditions differ in starburst...
One of the most exciting frontiers in extragalactic astronomy is understanding how rapidly galaxies formed stars in the Early Universe. This involves us constraining the Star Formation Rate Density (SFRD) at z >~ 6. Given the much greater ease in surveying the z > 4 universe in the rest-UV, the SFRD at z > 4 is biased to the unobscured, less dusty sources. Recent work shows that the...
We present an empirical galaxy evolution model, investigating the co-evolution of dark matter halos, galaxies, and supermassive black holes using from z= 0 - 10. Our approach connects the evolution of dark matter structure with simple empirical prescriptions for baryonic processes, allowing us to reproduce key observations in the relationship between galaxies and their black holes.
To...
In the literature, large amount of work has been devoted to the study of the build-up of metals and dust in disc galaxies. However, most of these analyses are based on global galactic properties. Therefore, spatially resolved studies are crucial to provide more detailed information on the evolution processes affecting these star forming galaxies.
In this talk, I will present a spatially...
Recent studies have revealed the existence of particularly massive galaxies within the first Gyr after the Big Bang. These findings push the limits of galaxy evolution models, but our understanding of the formation of such galaxies is limited due to a lack of sub-kpc resolution observations of bright, spectroscopically-confirmed targets.
The REBELS ALMA large program have observed [CII]...
Understanding how supermassive black holes and their host galaxies co-evolve in the universe is an unsolved problem. In a classical “unified” model for active galactic nuclei (AGN), observers can detect unobscured (Type-1) AGNs,with broad emission lines and continuum, or obscured (Type-2) AGNs, with only narrow emission lines. Type-2 AGNs have been readily identified at low redshift (z<1)....
Feedback from radio AGN has been observed in the form of jet driven gas outflows, which can affect the host galaxy’s evolution. Radio AGN are also known to have a life-cycle of activity. However it is still not completely clear how feedback evolves with the AGN life-cycle. In the first part of my talk, I will discuss our results from a study to investigate this with a sample of uniformly...
X-ray emission from young supernova remnants (SNRs) is characterized by non-thermal radiation and is usually interpreted as synchrotron process. This type of emission is detected in regions close to the shock front and it is explained with the the diffusive shock acceleration (DSA) theory, which requires high magnetic turbulence. However, the current spectral models used to fit the data...
Since the first detection by LIGO in 2015, gravitational-wave detectors observe mergers of black holes which formed in the low-metallicity, high-redshift Universe. A main uncertainty in our understanding of these mergers is the evolution of the progenitor stars of these black holes – stars more massive than ~20 solar masses. WC/WO stars are hot, post main-sequence stars with powerful winds...
The serendipitous appearances of Near-Earth Objects (NEOs) in a subset of the millions of archival exposures of optical and near-infrared astronomical imaging surveys can improve our knowledge of the orbits and compositions of NEOs. We show how the data processing and data mining of such imaging archives can be exploited to identify new and known NEOs, leading to a re-assessment of the impact...
4MOST is a new high-multiplex, wide-field spectroscopic survey facility under construction for ESO's 4m-VISTA telescope at Paranal, Chile. Its key specifications are: a large field of view of 4.4 square degrees, a high multiplex fibre positioner with 2436 science fibres, of which 1624 fibres go to two low-resolution spectrographs (R = λ/Δλ ~ 6500) and 812 fibres transfer light to the...
Ionization plays a critical role in the gas dynamics of protoplanetary disks (PPDs), which is further related with disk evolution and planet formation. While non-thermal ionization mechanisms, such as X-rays and cosmic rays, dominate the bulk regions of PPDs, the innermost regions are characterized by high temperatures (>1000K) with thermal ionization of alkali species and dust thermionic...
Collisions and interactions between galaxies are thought to be crucial phases in their evolution and mass assembly process, elevating star formation activity and potentially fueling accretion onto the central supermassive black holes. In this study, we leverage the high spatial resolution and sensitivity of the Hyper Suprime Cam survey and the associated rich multi-wavelength data in the GAMA...
The broad line region of active galactic nuclei, tightly connected to the central engine's activity, is still poorly understood. In this talk, we present an analysis of X-ray, UV and optical spectroscopic observations of the broad emission lines applied for the first time to a narrow-line Seyfert 1 (Juranova et al., to be subm.). For the panchromatic modelling of the broad-line emission, we...
In astronomy, machine learning has succeeded in various tasks, such as source localization, classification, anomaly detection, and segmentation. However, feature regression remains an area with room for improvement.
We aim to design a network that can accurately estimate sources’ features and their uncertainties from single-band image cutouts. The algorithm presented here,...
Next-generation weak gravitational lensing surveys, including Euclid, will be able to measure weak lensing signals with high statistical accuracy all the way into the regime probing the scales of non-linear collapse. To be able to exploit these measurements to the fullest extent and, in the end, most accurately determine the cosmology, we must have an accurate understanding of the baryonic...
We present two independent measurements of stellar velocity dispersions ( $\sigma_\mathrm{\star}$ ) from the Ca H K & Mg I region (388--555 nm) and the Calcium Triplet region (CaT, 835--875 nm) for 173 hard X-ray selected Type 1 AGNs from 105-month Swift-BAT catalog. We construct one of the largest samples of local Type 1 AGNs that have both single-epoch (SE), 'virial' black hole mass...
Are you considering a career change and would you like to remain closely involved in scientific research but from a different perspective? Maybe working at NWO, the Dutch research council, is something for you! NWO welcomes new employees with a scientific background to facilitate the funding of outstanding research and to help define strategies for funding research. Become a programme...
Galaxy mergers and accretions are a fundamental process in galaxy evolution. In the Milky Way, we can identify signatures of past galaxy accretion events as kinematic substructures, allowing us to characterize the property of each accreted galaxy and, potentially, its impact on the Milky Way's evolution. We here characterize the chemical properties of stars belonging to kinematic substructures...
We present results obtained by the Isaac Newton Telescope Wide Field Camera in March and April 2023 as part of a graduate class from Rijksuniversiteit Groningen. We present results from projects designed by the master students including: strategies to obtain a chromosome map of the globular cluster GCL38, a method to potentially determine metallicities making use of photometry and...
This presentation shows the status of the construction of the Extremely Large Telescope. It addresses both the infrastructure (telescope and building), as well as the instrument suite.
Images and graphics show the assembly status of the Dome and Main Structure on site in Chile, and the development of the mirrors and optomechanical control systems. Key figures are presented. Contracts...
Accretion is a fundamental astrophysical process, occurring across all scales of black hole mass. Despite its ubiquitous nature, the accretion process, alongside its connection to jet outflows, poses many fundamental questions. General Relativistic Magneto hydrodynamic (GRMHD) simulations are providing significant insights into the nature of black hole accretion and jet outflows. Following...
GRS 1915+105 regularly shows type-C quasi-periodic oscillations (QPOs) in the power density spectrum, sometimes together with a broad bump at around 30-150 Hz. We study the power spectra of GRS 1915+105 with the Rossi X-ray Timing Explorer when the source was in the hard-intermediate state. We find that the rms amplitude of the bump depends strongly upon both the frequency of the type-C QPO...
The distance of the outflowing wind is poorly constrained due to lack of direct imaging observations, which limits our understanding of their kinetic power. One way is that once known the density of the ionized plasma, the distance can be derived from the ionization parameter which measured based on the ionization states. Here, applying a new time-dependent photoionization model, TPHO, in...
We present the discovery of an AGN remnant associated with the galaxy group Abell 1318. Using GMRT and APERTIF data, we derive its radiative age and disentangle its complex history, showing that galaxy groups can have (surprisingly) dynamic past.
ED-2 is a stellar stream identified in integrals of motion on the third Gaia data release. It forms a compact group in energy and angular momentum in a local sample (<3 kpc), and its stellar population resembles one of an old metal-poor simple stellar population. It forms a compact group in the R-z (or x-z) plane, showing a ribbon-like structure in the solar neighbourhood, crossing the Sun's...
The Event Horizon Telescope (EHT) has recently published the first images of the supermassive black hole at the center of our Galaxy, Sagittarius A$^\ast$ (Sgr A$^\ast$ ). Imaging Sgr A$^\ast$ is plagued by two major challenges: variability on short (approximately minutes) timescales and interstellar scattering along our line of sight. While the scattering is well studied, the source...
The release of Gaia DR3 has substantially enriched our understanding of the current state of the Milky Way (MW), and its assembly history. A driving force behind this is the increase of stars with complete 6d phase space (positions and velocities) necessary for complex dynamical analysis, such as identifying stellar substructures in the MW's stellar halo. However, far more stars are still...
Comparison of horizon-scale observations of Sgr A and M87 with numerical simulations has provided considerable insight in their interpretation. Most of these simulations are variations of the same physical scenario consisting of a rotation-supported torus seeded with poloidal magnetic fields. This setup has several well known limitations, most notably, it differs in important ways from what...
Using stellar models from BPASS population synthesis, we calculate the full GW spectrum of a stellar population, including all types of compact binaries as well as those with living stars. We use these results to look at the detectability of star clusters with LISA. We find at late times the dominant sources are WD–WD binaries, but surprisingly at earlier times we find a significant population...
A key characteristic of some active galactic nuclei (AGN), such as radio galaxies, is that they possess powerful jets that can extend through or beyond their host galaxy. However, the exact mechanisms of their launch and their internal properties are still not well understood. In this talk, I will focus on Event Horizon Telescope (EHT) and multi-wavelength image and spectral observations of...
Upcoming surveys such as the Legacy Survey of Space and Time (LSST) will image billions of galaxies to extract the faint weak lensing signal for cosmological parameter inference. A pressing issue is that 50% of the galaxies will be “blended”, where its projection on our detectors will overlap with other astronomical objects along the same line of sight. Without appropriate “deblending”...
We report low-frequency radio observations of the 2021 outburst of the recurrent nova RS Ophiuchi. These observations include the lowest frequency observations of this system to date. Detailed light curves are obtained by MeerKAT at 0.82 and 1.28 GHz and LOFAR at 54 and 154 MHz. These low-frequency detections allow us to put stringent constraints on the brightness temperature that clearly...
After the Dark Ages, when the universe was completely neutral, the first sources of light appeared, marking the beginning of the Epoch of Reionization (EoR). During this epoch, the first stars and galaxies formed, emitting intense radiation that ionized the surrounding neutral hydrogen gas, creating ionized regions in the intergalactic medium (IGM), which grew and overlapped, making our...
I will present new results from two MeerKAT Large Survey Programs - The MeerKAT Fornax Survey (MFS) and MHONGOOSE. The exquisite combined sensitivity and resolution of the MeerKAT telescope has opened the door to exploring the realm of resolved, low column density (10^17 - 10^18 cm^-2) neutral hydrogen (HI) emission in a broad range of environments. In the Fornax cluster, we detect (and...
Recent observations of high redshift galaxies are unveiling unexpected properties of early galaxy-formation. Observations in both rest-frame ultraviolet with the James Webb Space Telescope and rest-frame far-infrared with the Atacama Large Millimeter Array suggest an early population of bright massive galaxy, with a significant dust-obscuration already at redshift 7. To better understand the...
We couple the DELPHI framework for galaxy formation with a model for the escape of ionizing photons to study both its variability with galaxy assembly and the resulting key reionization sources. In this model, leakage either occurs through a fully ionized gas distribution (ionization bounded) or additionally through channels cleared of gas by supernova explosions (ionization bounded + holes)....
The physical properties of the faint and extremely tenuous plasma in the filaments of the cosmic web remain one of the biggest unknowns in our story of large-scale structure evolution. The most common techniques how to observe this medium are either in emission, or in absorption against very bright, point-like sources. In this talk I focus on the warm-hot intergalactic medium and present yet...
The Decameter radio band (< 30 MHz) has been scarcily explored since the inception of radio astronomy, largely due to the perturbing effects of the ionosphere. However, the decameter wavelength band is an important part of the electromagnetic spectrum. In particular, decameter observations of radio halos in galaxy clusters will allow us to constrain the particle reaccerlation mechanisms...
While from a classical perspective we think of vacuum as empty space, it is filled by virtual particles from a quantum perspective. In flat spacetimes, these virtual particles arise in pairs, exist for a short amount of time, and then re-annihilate. As a result, no real particles are created.
In this talk, we show that real particles are created in curved spacetimes. This is because...
Habitable Worlds Observatory is a next-generation space telescope started by NASA following the recommendation of the US astronomy decadal survey in 2021. It will combine the key features of LUVOIR-B and HabEx projects and promises to provide unprecedented capabilities for exoplanetary science and astrophysics. As a continuation of our study for LUVOIR-A project, we propose a European-led,...
Polycyclic aromatic hydrocarbons (PAHs) are very stable molecules made of aromatic carbon rings. Their prominent infrared features were found in interstellar space, in asteroids, and are one form of carbon in circumstellar disks. Even though they are not the dominant form of carbon, these molecules can be easily observed making them an object of active research interest. Professor Carsten...
Cosmological simulations have been used to understand the formation of structure in the ΛCDM paradigm on small and large scales. Most simulations start with unconstrained Gaussian initial conditions, and therefore generically do not produce good analogues of the Local Group at present day. While constrained simulations exist, these have difficulty in precisely satisfying all our observational...
In recent decades, numerous telescopes have been built to identify transients and periodic variables in the night sky. These telescopes have provided a boom in our understanding of the wide variety of transients and their progenitor systems in many astrophysical contexts. While the Northern hemisphere has enjoyed several dedicated telescopes observing both transient and periodic phenomena on...
The Auger Engineering Radio Array (AERA) is an array of $153$ radio antennas spanning an area of 17 km$^2$, currently the largest of its kind, that probes the nature of ultra-high energy cosmic rays at energies around the transition from Galactic to extragalactic origin. It measures the MHz radio emission of extensive air showers produced by cosmic rays hitting our atmosphere. The elemental...
We develop a new technique to resolve small-scale structures in galaxy groups and clusters using XMM-MOS. This study takes advantage of the steep nature of the on-axis XMM PSF which encloses ~60% of the incident photon energy within 10 arcsec. Standard pipeline processing of XMM-MOS data yields images with 4 arcsec binning by default; however, images may be created with 1 arcsec bins to better...
Determining the circular velocity curve of a galaxy is a powerful tool for studying its overall shape. One can fit a potential and determine the dark matter distribution and density, or even the virial mass of the system.
One way of determining the rotation curve is through Jeans equations (Eilers et al. 2019, Ou et al. 2023). However, when using Jeans equations one needs to assume...
Anomalous flux ratios between lensed images can provide a key test of the dark matter sub-halo population, and hence the properties of dark matter particles. However, the observed anomalous flux ratios at radio frequencies can also be the result of systematics associated with our lack of knowledge about the source structure, source variability, and propagation effects within the lensing...
Hot-rocky exoplanets with surface temperatures above 1500 K are thought to support magma oceans. The presence of these magma oceans offers a unique opportunity for inferring the interior composition of these planets through the characterization of their atmosphere. With hundreds of hot-rocky exoplanets discovered and a dozen of good targets for JWST characterisation, understanding the links...
The spatial distribution of matter on the mega-parsec scale of the Universe forms a complex and highly anisotropic pattern termed the Cosmic Web or the Large-Scale Structure. In the study of the Cosmic Web, several tools and methodologies have been developed to inspect the properties of its different environments i.e. clusters, filaments, walls, and voids. In this work, we show that the...
With Gaia we have a thousand-fold increase in the number of stars and the precision with which we can observe their motion, which allows us to see previously rare phenomena in great numbers and detail. Astrometric binaries are a fantastic example of this - around half of all stars are binaries and precise astrometry enables us to detect a large fraction of these, with periods from months to...
Supernova (SN) feedback plays a fundamental role in galaxy evolution. However, modelling SN feedback in simulations of galaxy formation remains challenging because the simulations cannot resolve the scales on which SN feedback occurs. Therefore, SN feedback is generally implemented as a subgrid model that has a number of free parameters, which are calibrated such that the simulated galaxies...
Fast Radio Bursts (FRBs) are millisecond-duration transient sources of intense, coherent radiation originating in distant galaxies that are signposts of extreme astronomical environments. Telescopes all over the world are used to conduct searches for FRBs, localise them, and study their host galaxy and local environment. The European VLBI Network in particular is a prime instrument to study...
Runaway stars (massive stars moving away from the star clusters where they were born at unusually high velocities) have been observed for more than half a century, yet the origins of these high velocities remain elusive to this day. One of the most prominent theories for the origins of runaway stars is the dynamical ejection scenario in which binaries are thought to dynamically interact with...
High energy neutrinos(>10PeV) are integral to the multi-messenger astronomy and notoriously hard to detect. When a high energy neutrino interacts in ice, it produces a relativistic cascade of charged particles, which in turn leaves behind a plasma which can reflect radio waves. This is the concept of the Radar Echo Telescope (RET). But as a first step it's important to understand the method by...
The evolution of stars on grand time-scales affect their surroundings in many ways. Due to their intrinsic rotation, causing strong magnetic activity, they vary greatly in radiative activity in X-ray and ultraviolet (XUV) throughout their lifetime. Planets orbiting these stars close-in could, consequently, be affected by these drastic radiative changes. Close-in exoplanet atmospheres heat up...
The high angular resolution and sensitivity of VLBI offers a unique tool to identify and study AGN and star-formation activity. Radio imaging across a large range of angular scales is needed to determine the role of black hole feedback and jet-induced star formation in galaxies. All-sky VLBI surveys can answer these questions and find rare radio sources, such as gravitational lenses. Despite...
Supermassive black holes experience dynamical friction, a drag force caused by momentum exchange with the surrounding medium of stars, dark matter, and gas. In this study, we investigate dynamical friction on massive black holes in depth, including testing a commonly used analytic model based on Chandrasekhar's 1943 study. Our goal is to develop a functional subgrid model that can be...
Recent Event Horizon Telescope (EHT) observations of M87 and Sgr A have proven to be an insightful data set to probe the spacetime and physical conditions in accreting supermassive black hole systems. For this purpose an ad hoc and fixed, pre-computed library of ~60,000 model images for M87 and about 1,800,000 for Sgr A was used to sample black hole spin, magnetic flux on the horizon,...
X-ray binaries, which are neutron stars or black holes accreting gas from a companion star, emit radiation across the electromagnetic spectrum. Whereas it is well established where their X-ray and radio emission originates, it is much less clear where their infrared emission comes from: is it coming from the cooler outer part of the disk, the companion star, a jet, or a hot flow? During my...
Unveiling the mechanisms that trigger active galactic nuclei (AGN) is a badly understood problem, that is crucial for our understanding of the galaxy formation and evolution. While interactions and galaxy mergers are associated with the triggering of powerful AGN, less luminous AGN would be driven by secular processes (Treister et. al., 2012). Over the last few years, several observational...
At Leiden University's radio astronomy course, we observe the Milky Way using radio telescopes made of 5 litre paint cans, commercial Low Noise Amplifiers (LNAs) and Software Defined Radios (SDRs). Galactic neutral hydrogen can be detected on student's own laptops in mere seconds! This experiment involves the whole process from systems engineering, through signal processing, field experiments,...
The characteristic mass that sets the peak of the stellar initial mass function (IMF) is closely linked to the thermodynamic behaviour of interstellar medium (ISM), which controls how gas fragments as it collapses under gravity. As the Universe has grown in metal abundance over cosmic time, this thermodynamic behaviour has evolved from a primordial regime dominated by molecular hydrogen...
Wide-field Spectroscopic Telescope (WST) is a project of a next generation 10m-class telescope intended for spectroscopic surveys. It will include a multi-object spectrograph (MOS) unit covering a large field from 2.5 to 5 square degrees and providing medium (up to R7000) and high (R40 000) resolution spectra in the range of 360-1300 nm with a high multiplex of 20 000 and 2000, respectively....
A new era of high-resolution X-ray spectroscopy is upcoming. This spring, the JAXA/NASA (with SRON/UniGe/ESA participation) XRISM mission will be launched.
As already revealed by the short-lived Hitomi mission, the new vision on an energy band never explored before at high resolution, will bring transformational results.
In particular, the X-ray calorimeter, Resolve, will bring new insight...
Fast radio bursts (FRBs) are enigmatic astrophysical transients; they are brief, intense flashes of radio emission from extragalactic sources. The extreme brightness and millisecond-duration timescales of FRBs indicate that they are likely produced by compact objects with large energy reservoirs, such as accreting black holes or magnetars (ultra-magnetic neutron stars). Although most FRBs...
Radio observations are excellent probes of the environmental conditions in the coronae/magnetospheres of stars and brown dwarfs. In particular, radio emission traces the impact of stellar plasma on exoplanet atmospheres, the processes of coronal heating, and key parameters for assessing exo-habitability. The strong magnetic field of these stellar systems leads to radio emission via different...
Massive stars are the progenitors to a vast variety of observed highly energetic transients. Many of these transients are presumably the product of interaction between two or more stellar companions. Until recently, theoretical work has mainly focused on understanding the evolution of single- and binary stars. However, recent observations show that triple (and higher order multiple) star...
