Related papers: Can we improve CIV-based single epoch black hole m…
We study the angular resolution of the gravitational wave detector LISA and show that numerical relativity can drastically improve the accuracy of position location for coalescing Super Massive Black Hole (SMBH) binaries. For systems with…
We describe a method for determination of physical conditions in the broad line regions of a significant subsample of Seyfert-1 nuclei and quasars. Several diagnostic ratios based on intermediate (AlIII 1860, SiIII 1892) and high (CIV 1549,…
The Laser Interferometer Space Antenna's (LISA's) observation of supermassive binary black holes (SMBBH) could provide a new tool for precision cosmography. Inclusion of sub-dominant signal harmonics in the inspiral signal allows for…
Idealized models are used to illustrate the potential of the Laser Interferometer Space Antenna (LISA) as a probe of the largely unknown population of cosmologically-distant Massive Black Holes (MBHs) and as a tool to measure their masses…
The direct measurement of gravitational waves is a powerful tool for surveying the population of black holes across the universe. The first gravitational wave catalog from LIGO has detected black holes as heavy as $\sim50~M_\odot$,…
Indirect insights of Pop III stars and Black Holes (BHs) at Cosmic Dawn (CD) may be imprinted as an absorption signal in the 21cm line of HI against the CMB, when the Universe was less than 200 Myr old. To explain the additional large…
Quasar broad emission lines are largely powered by photoionization from the accretion continuum. Increased central luminosity will enhance line emissivity in more distant clouds, leading to increased average distance of the…
Supermassive black holes (SMBHs) with dynamically measured masses have shown empirical correlations with host galaxy properties. These correlations are often the only method available to estimate SMBH masses and gather statistics for large…
Horizon-scale imaging with the Event Horizon Telescope (EHT) has provided transformative insights into supermassive black holes but its resolution and scope are limited by ground-based constraints such as the size of the Earth, its…
We present new stringent limits on the mass $M_{bh}$ of the central supermassive black hole for a sample of 7 nearby galaxies. Our $M_{bh}$ estimates are based on the dynamical modeling of the central width of the nebular emission lines…
Presently, it is unclear whether the Eddington ratio and radiative efficiency depend upon a supermassive black hole's (SMBH's) redshift z and mass MBH. We attempt to resolve this issue using published data for 132,000 SMBHs with MBH >1E+7…
High-redshift quasars typically have their redshift determined from rest-frame ultraviolet (UV) emission lines. However, these lines, and more specifically the prominent C IV $\lambda 1549$ emission line, are typically blueshifted yielding…
Using bona-fide black hole (BH) mass estimates from reverberation mapping and the line ratio [SiVI] 1.963$\mu$m/Br$\gamma_{\rm broad}$ as tracer of the AGN ionising continuum, a novel BH-mass scaling relation of the form log($M_{\rm BH}) =…
Measuring of the masses of galactic supermassive black holes (SMBHs) is an important task, since they correlate with the host galaxy properties and play an important role in evolution of galaxies. Here we present a new method for measuring…
Intermediate-mass black holes (IMBHs) span the approximate mass range $100$--$10^5\,M_\odot$, between black holes (BHs) formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most…
We study the evolution of the binary black hole (BBH) mass distribution across cosmic time. The second gravitational-wave transient catalog (GWTC-2) from LIGO/Virgo contains BBH events out to redshifts $z \sim 1$, with component masses in…
We systematically investigate short-timescale ($<$10-day rest-frame) CIV broad absorption-line (BAL) variability to constrain quasar-wind properties and provide insights into BAL-variability mechanisms in quasars. We employ data taken by…
We have vastly increased the CIV statistics at intermediate redshift by surveying the thousands of quasars in the Sloan Digital Sky Survey Data-Release 7. We visually verified over 16,000 CIV systems with 1.46 < z < 4.55---a sample size…
We report the results of near-infrared spectroscopic observations of 37 quasars in the redshift range $6.3< z\le7.64$, including 32 quasars at $z>6.5$, forming the largest quasar near-infrared spectral sample at this redshift. The spectra,…
Using the statistics of pixel optical depths, we compare HI, CIV and CIII absorption in a set of six high quality z ~ 3-4 quasar absorption spectra to that in spectra drawn from two different state-of-the-art cosmological simulations that…