Aims. Massive black holes in the early Universe had limited time to assemble. We identify which JWST black-hole candidates place the strongest constraints on early growth models and assess how these constraints depend on mass estimates and growth assumptions. Methods. We compile 350 published measurements at $z\geq4$ and analyse a primary sample of 220 objects with broad Balmer-line...
Recent JWST observations of distant luminous galaxies and compact "little red dots" suggest the existence of early supermassive black holes (SMBHs) with masses $> 10^5\,M_\odot$. Their rapid emergence challenges conventional seeding and growth scenarios, motivating the question: could these SMBHs be seeded by primordial black holes (PBHs) formed from inflationary perturbations?
Explaining...
The Event Horizon Telescope (EHT) Collaboration produced the first image of the apparent shadow of the central black hole of Sagittarius A$^*$ (Sgr A$^*$). Sgr A$^*$ source structure varies significantly on timescales shorter than the duration of an observation, preventing improved data coverage through Earth rotation aperture synthesis. This rapid variability provides the opportunity to...
GW231123 is an exceptional binary black hole merger whose unusually large component masses challenge standard expectations for stellar origins. Additionally, its secondary mass (the less massive one) is in tension with the observed gravitational-wave population. Strong gravitational lensing provides a potential explanation, as magnification biases the inferred source parameters, making a...
Imaging Fourier-transform spectrographs (IFTS) such as SITELLE record spectral information by scanning a Michelson interferometer mirror and are reduced with the ORBS pipeline, which assumes conventional camera-style, frame-based exposures. We are developing a laboratory prototype IFTS built around Microwave Kinetic Inductance Detectors (MKIDs): energy-resolving, photon-counting sensors that...
Spectral indices are an effective technique for differentiating between thermal and non-thermal sources of radio emission. Most often, spectral indices are determined using flux measurements taken from multiple observations with different instruments. Since this data is not always available, finding indices from a single telescope observation is desirable. The reliability of these in-band...
The Cosmological Advanced Survey Telescope for Optical and UV Research (CASTOR) is a proposed 1 meter space telescope under development by the National Research Council of Canada, the Canadian Space Agency, and partner institutions around the world. It will serve as a successor to the Hubble Space Telescope (HST) at short wavelengths, providing continued access to the ultra-violet (UV) and...
The recent analyses of DESI DR2 BAO, Planck CMB and various Supernovae datasets have shown preferences for dynamic dark energy (DDE) over cosmological constant at various levels of significance, under frequentist model comparison tests. However, the same analysis done with a pure Bayesian model comparison test can lead to the opposite conclusions. In contrast to these traditional model...
Recent cosmological tensions have renewed interest in the role of reionization in cosmological parameter inference. In particular, “flash reionization” has been proposed as a transient episode of ionization at high redshift that could increase the Thomson optical depth, $\tau$, while remaining compatible with CMB polarization measurements.
In this work, we present the first Markov Chain Monte...
Understanding how supermassive black holes influence the galaxies they inhabit remains a central challenge in astrophysics. The most massive galaxies in the Universe—Brightest Cluster Galaxies at the centers of galaxy clusters—offer an exceptional laboratory to study this connection. Immersed in vast reservoirs of hot gas, their central black holes both accrete surrounding material and release...
Intermediate-mass black holes (IMBHs), with masses between $10^2$ and $10^5$$M_\odot$, may represent a missing link between stellar and supermassive black holes, yet few compelling candidates are known. In the Milky Way globular cluster Omega Centauri ($\omega$ Cen), Häberle et al. (2024) recently identified several stars near the cluster centre with projected velocities exceeding the escape...
Stars are rarely born alone, often existing in pairs. When one of these stars reaches the end of its life, it can collapse into a black hole, creating a black hole X-ray binary where it feeds off the matter of its companion star. This material spins rapidly, creating a hot accretion disk (emitting X-rays) while also launching powerful, outflowing jets (emitting radio waves). To understand how...
Dark matter may be made of ultra-light bosonic particles, so light that it behaves like a large-scale quantum wave rather than a swarm of individual particles ("ultralight" or "fuzzy" dark matter). This wave nature changes how massive objects like black holes move through it: the drag that normally causes objects to sink toward a galaxy's center can behave very differently.
Prior work on a...
Of the 2423 unassociated sources in the fourth data release of the fourth Fermi Large Area Telescope catalog (4FGL-DR4), 748 had also been observed by the Neil Gehrels Swift Observatory's X-ray telescope for $>4$~ks. Neumann et al. (2026) recently used a neural network classifier to identify new local pulsars and high-energy blazars from these unassociated sources, and they classified 173...
Accretion disks around black holes, such as those in active galactic nuclei and X-ray binaries, are home to extreme plasma processes that produce bright emission across the electromagnetic spectrum. One such process powering this emission is thought to be magnetic reconnection, the violent restructuring of the magnetic field topology in which magnetic field lines pinch apart and reconnect,...
Active galactic nuclei (AGN) are supermassive black holes in the centers of massive galaxies with large inflows of gas and dust collisionally heating up and radiating away energy. Quasars are a type of AGN that outshine their host galaxies by several magnitudes, capable of releasing high velocity outflows (or winds) of material due to the intense radiation being emitted. When these outflows...
