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Cosmological constraints from 21cm surveys after reionization
Eli Visbal, Abraham Loeb, Stuart Wyithe
21cm emission from residual neutral hydrogen after the epoch of reionization can be used to trace the cosmological power spectrum of density fluctuations. Using a Fisher matrix for…
Imaging the Black Hole Silhouette of M87: Implications for Jet Formation and Black Hole Spin
Avery E. Broderick, Abraham Loeb
The silhouette cast by the horizon of the supermassive black hole in M87 can now be resolved with the emerging millimeter very-long baseline interferometry (VLBI) capability. Despi…
The Race Between Stars and Quasars in Reionizing Cosmic Hydrogen
Abraham Loeb
The cosmological background of ionizing radiation has been dominated by quasars once the Universe aged by ~2 billion years. At earlier times (redshifts z>3), the observed abundance…
Evidence for Merger-Driven Activity in the Clustering of High Redshift Quasars
Stuart Wyithe, Abraham Loeb
Recently, a very large clustering length has been measured for quasars at a redshift of z~4. In combination with the observed quasar luminosity function we assess the implications…
Constraints on the Local Sources of Ultra High-Energy Cosmic Rays
Eli Waxman, Abraham Loeb
Ultra high-energy cosmic rays (UHECRs) are believed to be protons accelerated in magnetized plasma outflows of extra-Galactic sources. The acceleration of protons to ~10^{20} eV re…
Methods for detecting flaring structures in Sagittarius A* with high frequency VLBI
Sheperd S. Doeleman, Vincent L. Fish, Avery E. Broderick +2
The super massive black hole candidate, Sagittarius A*, exhibits variability from radio to X-ray wavelengths on time scales that correspond to < 10 Schwarzschild radii. We survey t…
Estimating the Parameters of Sgr A*'s Accretion Flow Via Millimeter VLBI
Avery E. Broderick, Vincent L. Fish, Sheperd S. Doeleman +1
Recent millimeter-VLBI observations of Sagittarius A* (Sgr A*) have, for the first time, directly probed distances comparable to the horizon scale of a black hole. This provides un…
Star Clusters Around Recoiled Black Holes in the Milky Way Halo
Ryan M. O'Leary, Abraham Loeb
Gravitational wave emission by coalescing black holes (BHs) kicks the remnant BH with a typical velocity of hundreds of km/s. This velocity is sufficiently large to remove the remn…
Acceleration of Galactic Supershells by Lyman Alpha Radiation
Mark Dijkstra, Abraham Loeb
Scattering of Lyman Alpha (hereafter Lya) photons by neutral hydrogen gas in a single outflowing 'supershell' around star forming regions often explains the shape and offset of the…
The 21cm Power Spectrum After Reionization
Stuart Wyithe, Abraham Loeb
We discuss the 21cm power spectrum (PS) following the completion of reionization. In contrast to the reionization era, this PS is proportional to the PS of mass density fluctuation…
Implications of Recent Measurements of the Milky Way Rotation for the Orbit of the Large Magellanic Cloud
Genevieve Shattow, Abraham Loeb
We examine the implications of recent measurements of the Milky Way rotation for the trajectory of the Large Magellanic Cloud. The ~ 14+/-6% increase in the MW circular velocity re…
Detecting Flaring Structures in Sagittarius A* with (Sub)Millimeter VLBI
Vincent L. Fish, Sheperd S. Doeleman, Avery E. Broderick +2
Multiwavelength monitoring observations of Sagittarius A* exhibit variability on timescales of minutes to hours, indicating emission regions localized near the event horizon. (Sub)…
Imprint of Inhomogeneous Hydrogen Reionization on the Temperature Distribution of the Intergalactic Medium
Hy Trac, Renyue Cen, Abraham Loeb
We study the impact of inhomogeneous hydrogen reionization on the thermal evolution of the intergalactic medium (IGM) using hydrodynamic + radiative transfer simulations where reio…
Lyman Alpha Driven Outflows Around Star Forming Galaxies
Mark Dijkstra, Abraham Loeb
We present accurate Monte-Carlo calculations of Lyman Alpha (hereafter Lya) radiation pressure in a range of models which represent galaxies during various epochs of our Universe.…
Gravitational waves from scattering of stellar-mass black holes in galactic nuclei
Ryan M. O'Leary, Bence Kocsis, Abraham Loeb
Stellar mass black holes (BHs) are expected to segregate and form a steep density cusp around supermassive black holes (SMBHs) in galactic nuclei. We follow the evolution of a mult…
Long-Term Evolution in Transit Duration of Extrasolar Planets from Magnetic Activity in their Parent Stars
Abraham Loeb
Existing upper limits on variations in the photospheric radius of the Sun during the solar magnetic activity cycle are at a fractional amplitude of 2x10^{-4}. At that level, the tr…
The Density Contrast of the Shapley Supercluster
Joseph A. Muñoz, Abraham Loeb
We calculate the density contrast of the Shapley Supercluster (SSC) based on the enhanced abundance of X-ray clusters in it using the extended Press-Schechter formalism. We derive…
Effects of gravitational-wave recoil on the dynamics and growth of supermassive black holes
Laura Blecha, Abraham Loeb
Simulations of binary black hole mergers indicate that asymmetrical gravitational wave (GW) emission can cause black holes to recoil at speeds up to thousands of km/s. These GW rec…
Let there be Light: the Emergence of Structure out of the Dark Ages in the Early Universe
Abraham Loeb
The initial conditions of our Universe can be summarized on a single sheet of paper. Yet the Universe is full of complex structures today, such as stars, galaxies and groups of gal…
Brightening of an Accretion Disk Due to Viscous Dissipation of Gravitational Waves During the Coalescence of Supermassive Black Holes
Bence Kocsis, Abraham Loeb
Mergers of supermassive black hole binaries release peak power of up to ~10^57 erg/s in gravitational waves (GWs). As the GWs propagate through ambient gas, they induce shear and a…
21cm Absorption by Compact Hydrogen Disks Around Black Holes in Radio-Loud Nuclei of Galaxies
Abraham Loeb
The clumpy maser disks observed in some galactic nuclei mark the outskirts of the accretion disk that fuels the central black hole and provide a potential site of nuclear star form…
Evolution of the 21 cm signal throughout cosmic history
Jonathan R. Pritchard, Abraham Loeb
The potential use of the redshifted 21 cm line from neutral hydrogen for probing the epoch of reionization is motivating the construction of several low-frequency interferometers.…
Limits on the Position Wander of Sgr A*
Mark J. Reid, Avery E. Broderick, Abraham Loeb +2
We present measurements with the VLBA of the variability in the centroid position of Sgr A* relative to a background quasar at 7-mm wavelength. We find an average centroid wander o…
Possibility of Precise Measurement of the Cosmological Power Spectrum With a Dedicated 21cm Survey After Reionization
Abraham Loeb, Stuart Wyithe
Measurements of the 21cm line emission by residual cosmic hydrogen after reionization can be used to trace the power spectrum of density perturbations through a significant fractio…