Related papers: Using variability and VLBI to measure cosmological…
The apparent position of jet base (core) in radio-loud active galactic nuclei changes with frequency because of synchrotron self-absorption. Studying this `core shift` effect enables us to reconstruct properties of the jet regions close to…
Active Galactic Nuclei (AGNs) are among the most luminous objects in the universe, making them valuable probes for studying galaxy evolution. However, understanding how AGN properties evolve over cosmic time remains a fundamental challenge.…
The cosmic proper distance $d_P$ is a fundamental distance in the Universe. Unlike the luminosity and angular diameter distances, which correspond to the angular size, the proper distance is the length of light path from the source to…
We study the black hole mass $-$ host galaxy stellar mass relation, $M_{\rm{BH}}-M_{\ast}$, of a sample of $z<4$ optically-variable AGNs in the COSMOS field. The parent sample of 491 COSMOS AGNs were identified by optical variability from…
The unified model of active galactic nuclei (AGN) includes a toroidal obscuring structure to explain the differences between Type I and Type II AGN as an effect of inclination angle. This toroidal structure is thought to be 'clumpy' as the…
We show that X-ray reverberation mapping can be used to measure the distance to type 1 active galactic nuclei (AGNs). This is because X-ray photons originally emitted from the `corona' close to the black hole irradiate the accretion disc…
Very Long Baseline Interferometry (VLBI) observations can provide the position of compact radio sources with an accuracy of order 50 micro-arcseconds. This is sufficient to measure the trigonometric parallax and proper motions of any object…
Active Galactic Nuclei (AGN) play a decisive role in galaxy evolution, particularly so when operating in a radiatively inefficient mode, where they launch powerful jets that reshape their surroundings. However, identifying them is…
High redshift active galactic nuclei (AGN) provide key insights into early supermassive black hole growth and cosmic evolution. This study investigates the parsec-scale properties of 86 radio-loud quasars at z $\geq$ 3 using very long…
Radio-loud active galactic nuclei (AGNs), hosting powerful relativistic jet outflows, provide an excellent laboratory for studying jet physics. Very long baseline interferometry (VLBI) enables high-resolution imaging on milli-arcsecond…
The detection of new clusters of galaxies or the study of known clusters of galaxies in X-rays can be complicated by the presence of X-ray point sources, the majority of which will be active galactic nuclei (AGN). This can be addressed by…
Less than $200$ radio-loud active galactic nuclei (AGN) are known above redshift $4$. Around $40$ of them have been observed at milliarcsecond (mas) scale resolution with very long baseline interferometry (VLBI) technique. Some of them are…
We correlate the positions of radio galaxies in the FIRST survey with the CMB lensing convergence estimated from the Atacama Cosmology Telescope over 470 square degrees to determine the bias of these galaxies. We remove optically…
The non-linear relation between X-ray and UV luminosity in quasars can be used to estimate their distance. Recently, we have shown that despite the large dispersion of the relation, a Hubble Diagram made of large samples of quasars can…
We investigate statistical and individual astrophysical properties of active galactic nuclei (AGNs), such as parsec-scale flux density, core dominance, angular and linear sizes, maximum observed brightness temperatures of VLBI core…
We present two catalogues of active galactic nucleus (AGN) candidates selected from the latest data of two all-sky surveys -- Data Release 2 (DR2) of the \emph{Gaia} mission and the unWISE catalogue of the \emph{Wide-field Infrared Survey…
We present an overview on how variability can be used to constrain the location of the ionized outflow in nearby Active Galactic Nuclei using high-resolution X-ray spectroscopy. Without these constraints on the location of the outflow, the…
We present a summary of the observation strategy of TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry), a monitoring program to study the parsec-scale structure and dynamics of relativistic jets in active…
We present the first results of an ongoing variability monitoring program of active galactic nuclei (AGNs) using the 46\,cm telescope of the Wise observatory in Israel. The telescope has a field of view of $1.25^{\circ} \times 0.84^{\circ}$…
We investigate a sample of 2293 ICRF2 extragalactic radio-loud sources with accurate positions determined by VLBI, mostly active galactic nuclei (AGN) and quasars, which are cross-matched with optical sources in the first Gaia release (Gaia…