The connection between X-ray weakness and powerful X-ray outflows is both expected in a scenario where outflows are connected with radiation-driven winds, and observed in several sources, both in the local Universe and at high redshift. Here I present the first results of a new study of this possible connection based on a search for SDSS quasars with weak X-ray emission in serendipitous XMM-Newton observations. The selected objects have a “normal” optical/UV blue continuum, but a flat and extraordinarily weak X-ray spectrum. The availability of rest-frame optical/UV spectra allows to check for the signature of outflows in the absorption lines and/or in the profiles of the emission lines. This method could reveal the presence of a population of so-far overlooked outflowing quasars and confirm the connection between winds and X-ray weakness in quasars.

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 (Lbol > 1047 erg/s) quasars at high redshift (z ∼ 2-4), unveiling interesting relations among active galactic nuclei, winds and interstellar medium, in these powerful sources at cosmic noon. Since 2022, we are performing a systematic and statistically-significant VLA study of the radio properties of WISSH. We carried out high-resolution VLA observations aiming at: 1) identifying young radio source from the broad-band spectral shape of these objects; 2) sample an unexplored high redshift/high luminosity regime, tracking possible evolutionary effects on the radio-loud/radio-quiet dichotomy; 3) quantifying orientation effects on the observed winds/outflows properties.

H2O megamaser emission from sub-parsec circumnuclear disks at the center of active galaxies allows a single-step, direct distance measurements to galaxies in the Hubble flow without any external calibration. Based on accurate distance determinations of six maser galaxies within 150 Mpc, the Megamaser Cosmology Project (MCP) team recently obtained H0 = 73.9± 3.0 km/s/Mpc (‘∼ 4% accuracy), independent of distance ladders and the cosmic microwave background. To further applying the megamaser technique to attain a 1% Ho measurement, detecting more high-quality disk maser systems is crucial. In this conference proceeding, we update the status of the MCP and discuss strategies of detecting additional high-quality disk maser galaxies within z ∼ 0.1. In addition, we show the prospects of reaching a 1% Ho measurement with the supreme sensitivity of the ngVLA. Finally, we demonstrate that applying the maser technique to distance measurements of high-z galaxies with future submm VLBI systems is promising and this will allow for investigation of the new tension between the ΛCDM model and the high-z Hubble diagram.

We consider evolution properties of galaxies and quasars with steep radio spectrum at the decametre band from the UTR-2 catalogue. The ratios of source's monochromatic luminosities at the decametre and high-frequency bands display the dependence on the redshift, linear size, characteristic age of examined objects. At that, the mean values of corresponding ratios for considered galaxies and quasars have enough close quantities,testifying on the unified model of sources. We analyse obtained relations for two types of steep-spectrum sources (with linear steep spectrum (S) and low-frequency steepness after a break (C+)) from the UTR-2 catalogue.

We observed an area of sky located within the SDSS Stripe 82 field at 1.6 GHz with the European VLBI Network (EVN). There are fifteen mJy/sub-mJy radio sources within the primary beam of a typical 30-m class EVN radio telescope. Our aim was to obtain information on compact radio structures of all VLBI-detectable sources within this primary beam area. The source of particular interest is the recently identified radio quasar J222843.54+011032.2 (J2228+0110) at z = 5.95. The data correlation was performed at the EVN software correlator at JIVE (SFXC). Three targets (J2228+0110, J222851.45+011203.4, J222941.76+011428.5) were detected, all three with position offsets not exceeding the 3σ accuracy of the original low-resolution radio surveys. The detection rate of 20% is consistent with other wide-field VLBI experiments carried out recently (e.g. Middelberg et al. 2013). The project presented here demonstrates the ability of EVN in multiple-phase-centre experiments and paves the way for future large-scale EVN surveys of compact structures in extragalactic radio sources using the multiple-phase-centre VLBI technique.

In this paper, we investigated the possible exponential decays in the long term optical light curve of the BL Lac {OJ 287}. We developed a method that can be used to decomposing a light curve into a linear combination of exponential decays. The decomposing shows that the decay time scales range from ~ 103.6 to ~ 10−4 days. The power spectra has frequency-dependent power-law with slop ~ 0.5, and the peak of power is at the time scale of decay on ~ 160 days.