Related papers: Radio Power from Direct-Collapse Black Holes
Observations with the James Webb Space Telescope (JWST) have revealed active galactic nuclei (AGN) powered by supermassive black holes (SMBHs) with estimated masses of $10^7-10^8$ M$_\odot$ at redshifts $z\sim7-9$. Some reside in…
The Sloan Digital Sky survey detected luminous quasars at very high redshift, z>6. Follow-up observations indicated that at least some of these quasars are powered by supermassive black holes (SMBHs) with masses in excess of billion solar…
Intermediate-mass black holes (IMBHs, $10^{3-6} \, \rm{M_\odot}$), are typically found at the center of dwarf galaxies and might be wandering, thus far undetected, in the Milky Way (MW). We use model spectra for advection-dominated…
Direct collapse within dark matter (DM) halos is a promising path to form supermassive black hole (SMBH) seeds at high redshifts. The outer part of this collapse remains optically thin, and has been studied intensively using numerical…
Over 60 years after the discovery of the first quasar, more than $275$ such sources are identified in the epoch of reionization at $z>6$. JWST is now exploring higher redshifts ($z\gtrsim 8$) and lower mass ($ \lesssim 10^7 \Msun$) ranges.…
Recent measurements of the cosmic X-ray and radio backgrounds (CXB/CRB, respectively) obtained with Chandra and ARCADE2 report signals in excess of those expected from known sources, suggesting the presence of a yet undiscovered population…
Thirteen dwarf galaxies have recently been found to host radio-selected accreting massive black hole (MBH) candidates, some of which are ``wandering" in the outskirts of their hosts. We present 9 GHz Very Long Baseline Array (VLBA)…
The recent discoveries of luminous quasars at high redshifts imply that black holes more massive than a few billion solar masses have been assembled already when the universe was less than a billion years old. We show that the existence of…
Observations of high-redshift quasars at z>6 imply that supermassive black holes (SMBHs) with masses over a billion solar masses were in place less than 1 Gyr after the Big Bang. If these SMBHs assembled from "seed" BHs left behind by the…
The gravitational waves generated during supermassive black hole (SMBH) coalescence are prime candidates for detection by the satellite LISA. We use the extended Press-Schechter formalism combined with empirically motivated estimates for…
We explore the possibility of detecting hydrogen radio recombination lines from 0 < z < 10 quasars. We compute the expected Hnalpha flux densities as a function of absolute magnitude and redshift by considering (i) the range of observed AGN…
Supermassive black holes are not only common in the present-day galaxies, but billion solar masses black holes also powered $z\geq 6$ quasars. One efficient way to form such black holes is the collapse of a massive primordial gas cloud into…
The existence of primordial black holes (PBHs), which may form from the collapse of matter overdensities shortly after the Big Bang, is still under debate. Among the potential signatures of PBHs are gravitational waves (GWs) emitted from…
The anticipated discovery of a pulsar in orbit with a black hole is expected to provide a unique laboratory for black hole physics and gravity. In this context, the next generation of radio telescopes, like the Five-hundred-metre Aperture…
In the standard Cold Dark Matter (CDM) theory of structure formation, virialized minihalos (with T_vir}<10^4 K) form in abundance at high redshift (z>6), during the cosmic ``dark ages.'' The hydrogen in these minihalos, the first nonlinear…
The next generation of electromagnetic and gravitational wave observatories will open unprecedented windows to the birth of the first supermassive black holes. This has the potential to reveal their origin and growth in the first billion…
The presence of an extra radio background besides the cosmic microwave background has important implications for the observation of the 21-cm signal during the cosmic Dark Ages, Cosmic Dawn, and epoch of Reionization. The strong absorption…
The presence of nine candidate galaxies at $z=17$ and $z=25$ discovered by the James Webb Space Telescope in relatively small sky areas, if confirmed, is virtually impossible to reconcile with the predictions of the current galaxy formation…
Massive Primordial Black Holes (MPBH) can be formed after inflation due to broad peaks in the primordial curvature power spectrum that collapse gravitationally during the radiation era, to form clusters of black holes that merge and…
Formation of significant number of primordial black holes (PBHs) is realized if and only if primordial density fluctuations have a large amplitude, which means that tensor perturbations generated from these scalar perturbations as a second…