Related papers: Proto-Quasars:Physical States and Observable Prope…

The idea that substantial absorption in AGN could be a definite characteristic of the early phases of QSO evolution was invoked to explain the submillimeter observations of X-ray absorbed AGN at z~1 to z~3, that have shown strong emission…

We compare the host galaxies properties of BL Lac objects with those of radio loud quasars (RLQs) imaged by the WFPC2 on board of HST. The considered objects (z<0.5) are always well resolved and their host galaxies satisfactorily modelled…

The intermediate results of the ongoing study of deep samples of ~200 galaxies residing in nearby voids, are presented. Their properties are probed via optical spectroscopy, ugri surface photometry, and HI 21-cm line measurements, with…

We make a detailed investigation of the properties of Lyman-break galaxies (LBGs) in the LambdaCDM model. We present predictions for two published variants of the GALFORM semi-analytical model: the Baugh et al. (2005) model, which has star…

We study the early growth of massive seed black holes (BHs) via accretion in protogalactic nuclei where the stellar bulge component is assembled, performing axisymmetric two-dimensional radiation hydrodynamical simulations. We find that…

Supercooled first-order phase transition (FOPT) can lead to the formation of primordial black holes (PBHs). This scenario imposes stringent requirements on the profile of the effective potential. In this work, we use the singlet extended…

We perform a Bayesian analysis of NANOGrav 15yr and IPTA DR2 pulsar timing residuals and show that the recently detected stochastic gravitational-wave background (SGWB) is compatible with a SGWB produced by bubble dynamics during a…

We report on the analysis of B band imaging data of 57 low-redshift QSOs and Seyfert 1 galaxies selected from the Hamburg/ESO-Survey, for which host galaxy dependent selection biases are greatly reduced compared to other optical surveys.…

We study the Primordial Black Hole (PBH) reheating scenario, where PBHs originate in a general cosmological background. In this scenario, ultralight PBHs with masses $M\lesssim 10^8$g temporarily dominate the Universe and reheat it via…

We present near-IR photometry and imaging observations of a small sample of sources identified in the BeppoSAX 5-10 keV survey (HELLAS) which resolves ~ 20-30% of the X-ray background at these energies. The near-IR data are combined with…

Links between the properties of radio-loud active galactic nuclei (RLAGNs) and the morphology of their hosts may provide important clues for our understanding of how RLAGNs are triggered. In this work, focusing on passive galaxies, we study…

We present the final results from our deep HST imaging study of the hosts of radio-quiet quasars (RQQs), radio-loud quasars (RLQs) and radio galaxies (RGs). We describe new WFPC2 R-band observations for 14 objects and model these images in…

Supermassive black hole (SMBH) binary systems are unavoidable outcomes of galaxy mergers. Their dynamics encode information about their formation and growth, the composition of their host galactic nuclei, the evolution of galaxies, and the…

The Quasar Luminosity Function (QLF) offers insight into the early co-evolution of black holes and galaxies. It has been characterized observationally up to redshift $z\sim6$ with clear evidence of a double power-law shape, in contrast to…

Astrophysical luminous objects such as the first stars have not yet formed in the Dark Ages. However, primordial black holes (PBHs) always exist throughout cosmic history since the inflation epoch. During the Dark Ages, PBHs may accrete the…

We use the spectra of 22,000 nearby early-type galaxies from the Sloan Digital Sky Survey (SDSS) to determine the age distribution of these galaxies as a function of their velocity dispersion sigma_v in the range 100 km/s < sigma_v < 280…

As it collapses to form a halo, the shape of a protohalo patch is deformed by the initial shear field. This deformation is often modeled using the "deformation" tensor, constructed from second derivatives of the gravitational potential,…

Sources at the brightest end of QSO luminosity function during the peak epoch of star formation and black hole accretion (z~2-4, i.e. Cosmic noon) are privileged sites to study the feeding & feedback cycle of massive galaxies. We perform…

We report the results of a pilot study of CO$(4-3)$ emission line of three {\it WISE}-selected hyper-luminous, dust-obscured quasars (QSOs) with sensitive ALMA Band 3 observations. These obscured QSOs with $L_{\rm bol}>10^{14}L_\odot$ are…

We present detailed observations of photoionization conditions and galaxy kinematics in eleven z$=1.39-2.59$ radio-loud quasar host galaxies. Data was taken with OSIRIS integral field spectrograph (IFS) and the adaptive optics system at the…