Results for "J. Stuart B. Wyithe"
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Reionization and Cosmology with 21 cm FluctuationsOct 16 2009Measurement of the spatial distribution of neutral hydrogen via the redshifted 21 cm line promises to revolutionize our knowledge of the epoch of reionization and the first galaxies, and may provide a powerful new tool for observational cosmology from ... More Detecting the redshifted 21cm forest during reionizationJan 28 2011Oct 25 2011The 21cm forest -- HI absorption features in the spectra of high-redshift radio sources -- can potentially provide a unique probe of the largely neutral intergalactic medium (IGM) during the epoch of reionization. We present simulations of the 21cm forest ... More Testing the Copernican Principle via Cosmological ObservationsJul 18 2008Jan 14 2009Observations of distances to Type-Ia supernovae can be explained by cosmological models that include either a gigaparsec-scale void, or a cosmic flow, without the need for Dark Energy. Instead of invoking dark energy, these inhomogeneous models instead ... More The Multi-Band Magnification Bias for Gravitational LensesAug 29 2002We present a generalization of the concept of magnification bias for gravitationally-lensed quasars, in which the quasars are selected by flux in more than one wavelength band. To illustrate the principle, we consider the case of two-band selection, in ... More Searching for MACHOs in Galaxy ClustersAug 10 2000If cluster dark matter is in the form of compact objects it will introduce fluctuations into the light curves of distant sources. Current searches for MACHOs in clusters of galaxies focus on monitoring quasars behind nearby systems. This paper considers ... More Photometric Variability in Earthshine ObservationsApr 06 2009The identification of an extrasolar planet as Earth-like will depend on the detection of atmospheric signatures or surface non-uniformities. In this paper we present spatially unresolved flux light curves of Earth for the purpose of studying a prototype ... More Dark Matter Annihilation in the First Galaxy HalosNov 14 2014May 13 2015We investigate the impact of energy released from self-annihilating dark matter on heating of gas in the small, high-redshift dark matter halos thought to host the first stars. A SUSY neutralino like particle is implemented as our dark matter candidate. ... More Determination of the transverse velocity of Q2237+0305Sep 21 1999The largest systematic uncertainty present in the analysis of gravitationally microlensed quasar light curves is that of the galactic transverse velocity. We describe a method for determining the transverse velocity as well as its application to published ... More Very Massive Stars in High-Redshift GalaxiesApr 12 2007Jun 27 2007A significant fraction of Lyman Alpha (Lya) emitting galaxies (LAEs) at z> 5.7 have rest-frame equivalent widths (EW) greater than ~100 Angstrom. However only a small fraction of the Lya flux produced by a galaxy is transmitted through the IGM, which ... More The 21cm Power Spectrum After ReionizationAug 18 2008Jul 24 2009We 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 fluctuations, with only a small modulation due to fluctuations in the ionization field ... More Fluctuations in 21cm Emission After ReionizationAug 26 2007The fluctuations in the emission of redshifted 21cm photons from neutral inter-galactic hydrogen will provide an unprecedented probe of the reionization era. Conventional wisdom assumes that this 21cm signal disappears as soon as reionization is complete, ... More Redshifted 21cm Signatures Around the Highest Redshift QuasarsJan 26 2004The Ly-alpha absorption spectrum of the highest redshift quasars indicates that they are surrounded by giant HII regions, a few Mpc in size. The neutral gas around these HII regions should emit 21cm radiation in excess of the Cosmic Microwave Background, ... More Gravitational Lensing of the SDSS High-Redshift QuasarsMar 08 2002May 23 2002We predict the effects of gravitational lensing on the color-selected flux-limited samples of z~4.3 and z>5.8 quasars, recently published by the Sloan Digital Sky Survey (SDSS). Our main findings are: (i) The lensing probability should be 1-2 orders of ... More The Imprint of Cosmic Reionization on Galaxy ClusteringJun 26 2007We consider the effect of reionization on the clustering properties of galaxy samples at intermediate redshifts (z~0.3-5.5). Current models for the reionization of intergalactic hydrogen predict that overdense regions will be reionized early, thus delaying ... More Dwarf Galaxy Formation Was Suppressed By Cosmic ReionizationMar 21 2006Mar 22 2006A large number of faint galaxies, born less than a billion years after the big bang, have recently been discovered. The fluctuations in the distribution of these galaxies contributed to a scatter in the ionization fraction of cosmic hydrogen on scales ... More Lyman Alpha Constraints on Very Low Luminosity AGNJun 14 2006Sep 21 2006Recent surveys have detected Lya emission from z=4.5-6.5 at luminosities as low as 10^41 erg/s. There is good evidence that low numbers of AGN are among observed faint Lya emitters. Combining these observations with an empirical relation between the intrinsic ... More Was the Universe Reionized by Massive Population-III Stars?Feb 17 2003Apr 10 2003The WMAP satellite has measured a large optical depth to electron scattering after cosmological recombination of 0.17+-0.04, implying significant reionization of the primordial gas only ~200 million years after the big bang. However, the most recent overlap ... More Reionization of Hydrogen and Helium by Early Stars and QuasarsSep 03 2002Nov 14 2002We compute the reionization histories of hydrogen and helium due to the ionizing radiation fields produced by stars and quasars. For the quasars we use a model based on halo-merger rates that reproduces all known properties of the quasar luminosity function ... More