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The detection of rapid variability on a time-scale of hours in radio-quiet quasars (RQQSOs) could be a powerful discriminator between starburst, accretion disc and relativistic jet models of these sources. This paper contains an account of…
We estimate how clustering in large-scale redshift surveys can constrain various cosmological parameters. Depth and sky coverage of modern redshift surveys are greater than ever, opening new possibilities for statistical analysis. We have…
We present a method for studying the proximity effect and the density structure around redshift z=2-3 quasars. It is based on the probability distribution of Lyman-alpha pixel optical depths and its evolution with redshift. We validate the…
We search for the most suitable set of cosmological parameters that describes the observable universe. The search includes the possibility of quintessential flat universes, i.e., the analysis is restricted to the determination of the…
Redshift drift refers to the phenomena that redshift of cosmic objects is a function of time. Measurement of redshift drift is of fundamental importance in physical cosmology and can be utilized to distinguish different cosmological models.…
Photometric Redshift is critical for analyzing astronomical objects, but existing ML methods often overlook the aleatoric uncertainties inherent in observed data. We introduce Starkindler, a novel training objective that explicitly…
We present new results of a study of the sub-millimetre continuum emission from a sample of 9 radio galaxies and 4 radio-quiet quasars at redshifts $z = 0.75 - 4.26$. The observations were made at 800$\mu m$, using the single-element…
Quasars are variable on timescales from days to years in UV/optical, and generally appear bluer while they brighten. The physics behind the variations in fluxes and colors remains unclear. Using SDSS g and r band photometric monitoring data…
In the past years, the results obtained by the WISSH quasar project provided a novel general picture on the distinctive multi-band properties of hyper-luminous ($L_{bol}>10^{47}$ erg/s) quasars at high redshift (z$\sim$2-4), unveiling…
The Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory is poised to observe thousands of quasars using the Deep Drilling Fields (DDF) across six broadband filters over a decade. Understanding quasar accretion disc (AD)…
Galaxies hosting z~2 quasars are the high-$z$ progenitors of today's massive `red-and-dead' galaxies. With close pairs of quasars at different redshifts, a background quasar can be used to study a foreground quasar's halo gas in absorption,…
From the first observations made by Slipher, our understanding and interpretation of the cosmological redshift was evolving until reaching the current consensus, through the expanding universe and the emergence of modern physical cosmology…
We study the environments of low redshift (z < 0.5) quasars based on a large and homogeneous dataset from the Stripe 82 region of the Sloan Digital Sky Survey (SDSS). We have compared the < 1 Mpc scale envi- ronments of 302 quasars that…
We investigate how galaxy-galaxy lensing measurements depend on the knowledge of redshifts for lens and source galaxies. Galaxy-galaxy lensing allows one to study dark matter halos of galaxies statistically using weak gravitational lensing.…
I review recent observations on the evolution of quasars, describe new surveys for quasars at z > 5 and for quasars at z > 3.3 down to luminosities corresponding to L* galaxies, and note the possible connection between the evolution of the…
We develop a cosmological parameter estimation code for (tomographic) angular power spectra analyses of galaxy number counts, for which we include, for the first time, redshift-space distortions (RSD) in the Limber approximation. This…
Photometric redshifts play an important role as a measure of distance for various cosmological topics. Spectroscopic redshifts are only available for a very limited number of objects but can be used for creating statistical models. A broad…
Using a new recently compiled milliarcsecond compact radio data set of 120 intermediate-luminosity quasars in the redshift range $0.46< z <2.76$, whose statistical linear sizes show negligible dependence on redshifts and intrinsic…
We study the dependence of the number density and properties of quasars on the background galaxy density using the currently largest spectroscopic datasets of quasars and galaxies. We construct a galaxy number density field smoothed over…
Extremely Red Quasars (ERQs) are thought to represent a brief episode of young quasar and galactic evolution characterized by rapid outflows and obscured growth due to dusty environments. We use new redshift measurements from CO and…