Related papers: Prospects for observing supermassive black hole bi…
Primordial black holes (PBHs) with log-normal mass spectrum with masses up to $\sim 10^4-10^5 M_\odot$ can be created after QCD phase transition in the early Universe at $z\sim 10^{12}$ by the modified Affleck-Dine baryogenesis. Using a…
We model the electromagnetic emission signatures of massive black hole binaries (MBHBs) with an associated gas component. The method comprises numerical simulations of relativistic binaries and gas coupled with calculations of the physical…
We investigate the theoretical expectations for detections of supermassive binary black holes that can be identified as sub-parsec luminous quasars. To-date, only two candidates have been selected in a sample comprising 17,500 sources…
Intermediate-mass black holes (IMBHs; $M_{BH} <2*10^{5} M_{\odot}$) in galaxy centers are cruciel for painting a coherent picture of the formation and growth of supermassive black holes (SMBHs). Using Big Data analysis, we identified 305…
The broad emission spectral lines emitted from AGNs are our main probe of the geometry and physics of the broad line region (BLR) close to the SMBH. There is a group of AGNs that emits very broad and complex line profiles, showing two…
We present a sample of intermediate-mass black hole (IMBH) candidates based on the detection of a broad H$\alpha$ emission line and variability, which are selected from the Sloan Digital Sky Survey Data Release 7. By performing spectral…
Supermassive black hole binary systems (SMBHBs) are thought to emit the recently discovered nHz gravitational wave background; however, not a single individual nHz source has been confirmed to date. Long-term radio-monitoring at the Owens…
The origin of supermassive black holes (SMBHs) is a pivotal problem in modern cosmology. This work explores the potential of the Taiji-TianQin space-borne gravitational-wave (GW) detector network to identify the formation channels of…
Supermassive black hole binaries (SMBHBs) formed in galaxy mergers are promising multi-messenger sources. They can be identified as quasars with periodic variability in electromagnetic (EM) time-domain surveys. The most massive of those…
In this paper, we study and compare the optical and X-ray counterparts of subparsec supermassive black hole binaries (SMBHBs). With that aim, we simulated the profiles of optical spectral lines emitted from the broad line region (BLR) as…
We present a novel formation channel for supermassive black hole (SMBH) binaries in the early Universe, driven by primordial black holes (PBHs). Using high-resolution hydrodynamical simulations, we explore the role of massive PBHs ($m_{BH}…
Hierarchical assembly models predict a population of supermassive black hole (SMBH) binaries. These are not resolvable by direct imaging but may be detectable via periodic variability (or nanohertz frequency gravitational waves). Following…
Coalescing massive black hole binaries are powerful emitters of gravitational waves, in the LISA sensitivity range for masses M_BH ~ 10^{4-7} M_sun. According to hierarchical galaxy merger models, binary black holes should form frequently,…
Spectropolarimetric efforts in the last few years have provided an efficient method that is based on the profiles of the polarization plane position angle of broad emission lines in active galactic nuclei (AGNs). Here we present black hole…
Supermassive black holes (SMBHs) reside at the center of every massive galaxy in the local Universe with masses that closely correlate with observations of their host galaxy implying a connected evolutionary history. The population of…
Supermassive black holes (SMBHs) are found in the centers of massive galaxies, and galaxy mergers should eventually lead to SMBH mergers. Quasar activity has long been associated with galaxy mergers, so here we investigate if supermassive…
Intermediate-mass black holes (IMBHs), with masses between roughly $10^2\,M_\odot$ and $10^5\,M_\odot$, represent a largely uncharted component of the black-hole (BH) population. They are theoretically predicted to form in several…
The gravitational-wave background from supermassive binary black holes (SMBBHs) has yet to be detected. This has led to speculations as to whether current pulsar timing array limits are in tension with theoretical predictions. In this…
Supermassive black holes are commonly found in the center of galaxies and evolve with their hosts. The supermassive binary black holes (SMBBH) are thus expected to exist in close galaxy pairs, however, none has been unequivocally detected.…
We present Hubble Space Telescope ultraviolet (UV) of 13 quasars at z<0.7, along with contemporaneous optical spectra from ground-based telescopes. The targets were selected to have broad H-beta emission lines with substantial velocity…