Results for "Asantha Cooray"

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Non-linear Integrated Sachs-Wolfe EffectSep 10 2001We discuss the non-linear extension to the integrated Sachs-Wolfe effect (ISW) resulting from the divergence of the large scale structure momentum density field. The non-linear ISW effect leads to an increase in the total ISW contribution by roughly two ... More
Cross-Correlation Studies with CMB Polarization MapsNov 21 2003May 10 2004The free-electron population during the reionized epoch rescatters CMB temperature quadrupole and generates a now well-known polarization signal at large angular scales. While this contribution has been detected in the temperature-polarization cross power ... More
Weak Lensing of the CMB: Power Spectrum CovarianceOct 18 2001We discuss the non-Gaussian contribution to the power spectrum covariance of cosmic microwave background (CMB) anisotropies resulting through weak gravitational lensing angular deflections and the correlation of deflections with secondary sources of temperature ... More
Applications of Halo Approach to Non-Linear Large Scale Structure ClusteringMay 24 2001We present astrophysical applications of the recently popular halo model to describe large scale structure clustering. We formulate the power spectrum, bispectrum and trispectrum of dark matter density field in terms of correlations within and between ... More
Distances and Cosmology From Galaxy Cluster CMB DataMay 27 2003The measurement of angular diameter distance to galaxy clusters, through combined Sunyaev-Zel'dovich (SZ) effect data with X-ray emission observations, is now a well-known probe of cosmology. Using a combination of SZ data and a map of the lensed CMB ... More
Kuiper Belt Object Sizes and Distances from Occultation ObservationsApr 22 2003There are several observational campaigns under way to detect kilometer size foreground Kuiper Belt Objects (KBOs) through their occultation of background stars. The interpretation of an occultation light curve, unfortunately, is affected by a geometric ... More
Modifications to the Cosmic 21-cm Background Frequency Spectrum by Scattering via electrons in Galaxy ClustersNov 09 2005May 07 2006The cosmic 21-cm background frequency spectrum related to the spin-flip transition of neutral Hydrogen present during and before the era of reionization is rich in features associated with physical processes that govern transitions between the two spin ... More
Lensing Studies with Diffuse BackgroundsSep 10 2003The current weak lensing measurements of the large scale structure are mostly related to statistical study of background galaxy ellipticities. We consider a possibility to extend lensing studies with intrinsically unresolved sources and suggest that spatial ... More
Large Scale Pressure Fluctuations and Sunyaev-Zel'dovich EffectMay 12 2000Jul 15 2000The Sunyaev-Zel'dovich (SZ) effect associated with pressure fluctuations of the large scale structure gas distribution will be probed with current and upcoming wide-field small angular scale cosmic microwave background experiments. We study the generation ... More
Cross-Correlation Studies between CMB Temperature Anisotropies and 21 cm FluctuationsMay 26 2004During the transition from a neutral to a fully reionized universe, scattering of cosmic microwave background (CMB) photons via free-electrons leads to a new anisotropy contribution to the temperature distribution. If the reionization process is inhomogeneous ... More
After MAP: Next Generation CMBNov 15 2002We discuss several opportunities involving cosmic microwave background (CMB) observations during the post-MAP era. The curl-modes of CMB polarization allow a direct detection of inflationary gravitational waves and a measurement of the energy scale of ... More
Kuiper Belt and Oort Cloud Objects: Microlenses or Stellar Occulters?Sep 25 2002The occultation of background stars by foreground Solar system objects, such as planets and asteroids, has been widely used as an observational probe to study physical properties associated with the foreground sample. Similarly, the gravitational microlensing ... More
Angular Diameter Distance Measurement with Galaxy Clustering in the Multipole SpaceJul 06 2006The shape of the angular power spectrum of galaxies in the linear regime is defined by the horizon size at the matter-radiation equality. When calibrated by cosmic microwave background measurements, the shape of the clustering spectrum can be used as ... More
Are galaxy properties only determined by the dark matter halo mass?Jan 04 2006Conditional luminosity function (CLF) of dark matter halos supersedes simple models on the number of galaxies as a function of the halo mass, or the so-called halo occupation number, by assigning a luminosity distribution to those galaxies. Suggestions ... More
Extragalactic Background Light: Measurements and ApplicationsFeb 10 2016This review covers the measurements related to the extragalactic background light (EBL) intensity from gamma-rays to radio in the electromagnetic spectrum over 20 decades in the wavelength. The cosmic microwave background (CMB) remains the best measured ... More
Impact of Secondary non-Gaussianities on the Search for Primordial Non-Gaussianity with CMB MapsJan 21 2008When constraining the primordial non-Gaussianity parameter f_NL with cosmic microwave background anisotropy maps, the bias resulting from the covariance between primordial non-Gaussianity and secondary non-Gaussianities to the estimator of f_NL is generally ... More
The Born and Lens-Lens Corrections to Weak Gravitational Lensing Angular Power SpectraJan 10 2006Mar 10 2006We revisit the estimation of higher order corrections to the angular power spectra of weak gravitational lensing. Extending a previous calculation of Cooray and Hu, we find two additional terms to the fourth order in potential perturbations of large-scale ... More
Weak Lensing of the Cosmic Microwave Background by Foreground Gravitational WavesApr 07 2006Jul 13 2006Weak lensing distortion of the background cosmic microwave background (CMB) temperature and polarization patterns by the foreground density fluctuations is well studied in the literature. We discuss the gravitational lensing modification to CMB anisotropies ... More
The X-ray Background-Foreground Galaxy Cross-Correlation: Evidence for Weak Lensing?Jun 16 1999Jul 02 1999A significant cross-correlation between the unresolved X-ray background (XRB) at soft energies (0.5 to 2 keV) and foreground bright galaxies has now been reported in several studies. This cross-correlation has been interpreted in terms of a low redshift ... More
An SZ Temperature Decrement - X-ray Luminosity Relation for Galaxy ClustersMay 07 1999We present the observed relation between the cosmic microwave background (CMB) temperature decrement due to the Sunyaev-Zeldovich (SZ) effect and the X-ray luminosity of galaxy clusters. We discuss this relation in terms of the cluster properties, and ... More
Galaxy Clusters: Oblate or Prolate?May 07 1999Dec 06 1999It is now well known that a combined analysis of the Sunyaev-Zel'dovich (SZ) effect and the X-ray emission observations can be used to determine the angular diameter distance to galaxy clusters, from which the Hubble constant is derived. Given that the ... More
Gravitational Lensing Limits on the Average Redshift of Submillimeter SourcesDec 23 1998The submillimeter universe has now been explored with the Submillimeter Common User Bolometer Array (SCUBA) camera on the James Clerk Maxwell Telescope, and a claim has been made to the presence of a new population of optically unidentified starforming ... More
Gravitationally Lensed Sub-mm Sources towards Galaxy ClustersSep 07 1998Recent observations of galaxy clusters with the SCUBA instrument on the James Clarke Maxwell Telescope have revealed a sample of gravitationally lensed sources at sub-mm wavelengths. We extend our previous calculation on the expected number of lensed ... More
Cosmology with Galaxy Clusters: II. Projection Effects on Hubble Constant and Gas Mass FractionAug 18 1998It is well known that a combined analysis of the Sunyaev-Zel'dovich (SZ) effect and the X-ray emission observations can be used to determine the angular diameter distance to galaxy clusters, from which the Hubble constant is derived. The present values ... More
Did WMAP see Moving Local Structures?Oct 05 2005The divergence of the momentum density field of the large scale structure generates a secondary anisotropy contribution to the Cosmic Microwave Background (CMB). While the effect is best described as a non-linear extension to the well-known integrated ... More
Graviton Mass from Close White Dwarf Binaries Detectable with LISANov 03 2003Feb 18 2004The arrival times of gravitational waves and optical light from orbiting binaries provide a mechanism to understand the propagation speed of gravity when compared to that of light or electromagnetic radiation. This is achieved with a measurement of any ... More
Dissipationless Merging and the Assembly of Central GalaxiesMar 29 2005We reanalyze the galaxy-mass correlation function measured by the Sloan Digital Sky Survey to obtain host dark matter halo masses at galaxy and galaxy group scales. We extend the data to galaxy clusters in the 2MASS catalog and study the relation between ... More
The Rise of Dwarfs and the Fall of Giants: Galaxy Formation Feedback Signatures in the Halo Satellite Luminosity FunctionJun 19 2005The observed luminosity function (LF) of satellite galaxies shows several interesting features that require a better understanding of gas-thermodynamic processes and feedback effects related to reionization and galaxy formation. In galaxy clusters, the ... More
Cosmic 21-cm Delensing of Microwave Background Polarization and the Minimum Detectable Energy Scale of InflationFeb 28 2005The curl (B) modes of cosmic microwave background (CMB) polarization anisotropies are a unique probe of the primordial background of inflationary gravitational waves (IGWs). Unfortunately, the B-mode polarization anisotropies generated by gravitational ... More
Weighing Neutrinos: Weak Lensing ApproachApr 19 1999Jun 16 1999We study the possibility for a measurement of neutrino mass using weak gravitational lensing. The presence of non-zero mass neutrinos leads to a suppression of power at small scales and reduces the expected weak lensing signal. The measurement of such ... More
An Upper Limit on Omega_matter Using Lensed ArcsApr 19 1999May 05 1999We use current observations on the number statistics of gravitationally lensed optical arcs towards galaxy clusters to derive an upper limit on the cosmological mass density of the Universe. The gravitational lensing statistics due to foreground clusters ... More
Gravitationally Lensed muJy Radio Sources towards Galaxy ClustersJul 14 1998Galaxy clusters are expected to gravitationally lens background radio sources. However, due to the smaller surface density of radio sources, when compared to optical galaxies, such lensed events are rare. For an example, it is expected that there is no ... More
Radio Emission towards Lensed Arcs in Galaxy ClustersFeb 10 1998We present initial results from a search to detect radio emission at 1.4 GHz from gravitationally lensed arcs towards galaxy clusters. Using the FIRST survey observations of galaxy cluster fields, we have clearly detected 1.4 GHz emission at the location ... More
Search for Small-Mass Black Hole Dark Matter with Space-Based Gravitational Wave DetectorsMay 11 2004The high sensitivity of upcoming space-based gravitational wave detectors suggests the possibility that if halo dark matter were composed of primordial black holes (PBHs) with mass between $10^{16}$ g and 10$^{20}$ g, the gravitational interaction with ... More
Cosmological Constraints on the Very Low Frequency Gravitational-Wave BackgroundFeb 02 2005While there are no strong observational constraints on the gravitational wave background across six or more orders of magnitude between 10^{-16} Hz and 10^{-10} Hz and it is difficult to get a constraint below 10^{-12}Hz using objects in our Galaxy, we ... More
Gravitational Time Delay Effects on CMB AnisotropiesJul 31 2000We study the effect of gravitational time delay on the power spectra and bispectra of the cosmic microwave background (CMB) temperature and polarization anisotropies. The time delay effect modulates the spatial surface at recombination on which temperature ... More
Power Spectrum Covariance of Weak Gravitational LensingDec 05 2000Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters which govern them. At low redshifts, the non-linear gravitational evolution of large scale structure produces a non-Gaussian ... More
Weak Gravitational Lensing BispectrumApr 11 2000Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters which govern them. The non-linear evolution of large scale structure produces a non-Gaussian signal which is potentially observable ... More
Sunyaev-Zeldovich Fluctuations from the First Stars?Mar 02 2003Mar 08 2003WMAP's detection of high electron-scattering optical depth suggests substantial star formation at high redshift z~17 +/- 5. On the other hand, the recovered sigma_8 ~ 0.84 +/-0.04 disfavors a cluster Sunyaev-Zeldovich (SZ) origin for the observed small-scale-CMB ... More
Dusty Star-Forming Galaxies at High RedshiftFeb 06 2014Far-infrared and submillimeter wavelength surveys have now established the important role of dusty, star-forming galaxies (DSFGs) in the assembly of stellar mass and the evolution of massive galaxies in the Universe. The brightest of these galaxies have ... More
The inflationary gravitational-wave background and measurements of the scalar spectral indexFeb 12 2008Inflation predicts a stochastic background of gravitational waves over a broad range of frequencies, from those accessible with cosmic microwave background (CMB) measurements, to those accessible directly with gravitational-wave detectors, like NASA's ... More
Direct detection of the inflationary gravitational wave backgroundJun 17 2005Mar 01 2006Inflation generically predicts a stochastic background of gravitational waves over a broad range of frequencies, from those accessible with cosmic microwave background (CMB) measurements, to those accessible directly with gravitational-wave detectors, ... More
Growth Rate of Large Scale Structure as a Powerful Probe of Dark EnergyApr 14 2003The redshift evolution of the growth rate of the gravitational potential, d(D/a)/dz, is an excellent discriminator of dark energy parameters and, in principle, more powerful than standard classical tests of cosmology. This evolution is directly observable ... More
The trispectrum of 21-cm background anisotropies as a probe of primordial non-GaussianityJan 22 2008The 21-cm anisotropies from the neutral hydrogen distribution prior to the era of reionization is a sensitive probe of primordial non-Gaussianity. Unlike the case with cosmic microwave background, 21-cm anisotropies provide multi-redshift information ... More
Weak Lensing of the CMB: Cumulants of the Probability Distribution FunctionAug 16 2002We discuss the real-space moments of temperature anisotropies in the cosmic microwave background (CMB) due to weak gravitational lensing by intervening large-scale structure. We show that if the probability distribution function of primordial temperature ... More
Separation of Gravitational-Wave and Cosmic-Shear Contributions to Cosmic Microwave Background PolarizationFeb 23 2002May 14 2002Inflationary gravitational waves (GW) contribute to the curl component in the polarization of the CMB. Cosmic shear--gravitational lensing of the CMB-- converts a fraction of the dominant gradient polarization to the curl component. Higher-order correlations ... More
A Halo Model of Local IRAS Galaxies Selected at 60 Micron Using Conditional Luminosity FunctionsOct 26 2010Using conditional luminosity functions (CLFs) which encode the luminosity distribution of galaxies as a function of halo mass, we construct a halo model of IRAS galaxies selected at 60 micron. An abundance matching technique is used to link galaxy luminosity ... More
Statistical Imprints of SZ Effects in the Cosmic Microwave BackgroundSep 30 2004We review several aspects of the Sunyaev-Zel'dovich (SZ) effect associated with the large scale baryon distribution and its characteristic signatures in the statistics of cosmic microwave background (CMB) anisotropies. We discuss (1) the contributions ... More
Constraints on the SZ Power Spectrum on Degree Angular Scales in WMAP DataFeb 26 2010Jul 16 2011The Sunyaev-Zel'dovich (SZ) effect has a distinct spectral signature that allows its separation from fluctuations in the cosmic microwave background (CMB) and foregrounds. Using CMB anisotropies measured in Wilkinson Microwave Anisotropy Probe's five-year ... More
The Impact of Secondary non-Gaussianities in the CMB on Cosmological Parameter EstimationSep 19 2009Jul 13 2010We consider corrections to the underlying cosmology due to secondary contributions from weak gravitational lensing, the integrated Sachs-Wolfe effect, and the Sunyaev-Zel'dovich effect contained in the trispectrum. We incorporate these additional contributions ... More
On the origin of the cosmic microwave background anisotropiesMar 30 2007Suggestions have been made that the microwave background observed by COBE and WMAP and dubbed Cosmic Microwave Background (CMB) may have an origin within our own Galaxy or Earth. To consider the signal that may be correlated with Earth, a correlate-by-eye ... More
Cosmology with intensity mapping techniques using atomic and molecular linesJul 18 2016Dec 07 2016We present a systematic study of the intensity mapping technique using updated models for the different emission lines from galaxies and identify which ones are more promising for cosmological studies of the post reionization epoch. We consider the emission ... More
Foreground contamination in Ly-alpha intensity mapping during the epoch of reionizationDec 06 2013Feb 28 2014The intensity mapping of Ly-alpha emission during the epoch of reionization (EoR) will be contaminated by foreground emission lines from lower redshifts. We calculate the mean intensity and power spectrum of Ly-alpha emission at z~7, and estimate the ... More
Phenomenology of D-Brane Inflation with General Speed of SoundJun 09 2007Nov 24 2008A characteristic of D-brane inflation is that fluctuations in the inflaton field can propagate at a speed significantly less than the speed of light. This yields observable effects that are distinct from those of single-field slow roll inflation, such ... More
Constraints on primordial non-Gaussianity from WMAP7 and Luminous Red Galaxies power spectrum and forecast for future surveysApr 30 2010Oct 09 2010We place new constraints on the primordial local non-Gaussianity parameter f_NL using recent Cosmic Microwave Background anisotropy and galaxy clustering data. We model the galaxy power spectrum according to the halo model, accounting for a scale dependent ... More
Impact of Point Source Clustering on Cosmological Parameters with CMB AnisotropiesJun 10 2008The faint radio point sources that are unresolved in cosmic microwave background (CMB) anisotropy maps are likely to be a biased tracer of the large-scale structure dark matter distribution. While the shot-noise contribution to the angular power spectrum ... More
Red Density Perturbations and Inflationary Gravitational WavesJul 17 2007We study the implications of recent indications for a red spectrum of primordial density perturbations for the detection of inflationary gravitational waves (IGWs) with forthcoming cosmic microwave background experiments. We find that if inflation occurs ... More
Lensing and Supernovae: Quantifying The Bias on the Dark Energy Equation of StateOct 22 2007Jan 30 2008The gravitational magnification and demagnification of Type Ia supernovae (SNe) modify their positions on the Hubble diagram, shifting the distance estimates from the underlying luminosity-distance relation. This can introduce a systematic uncertainty ... More
Implications of Two Type Ia Supernova Populations for Cosmological MeasurementsJun 19 2008Jul 21 2008Recent work suggests that Type Ia supernovae (SNe) are composed of two distinct populations: prompt and delayed. By explicitly incorporating properties of host galaxies, it may be possible to target and eliminate systematic differences between these two ... More
Solar System: Sifting through the debrisAug 11 2006A quadrillion previously unnoticed small bodies beyond Neptune have been spotted as they dimmed X-rays from a distant source. Models of the dynamics of debris in the Solar System's suburbs must now be reworked.
Non-linear Galaxy Power Spectrum and Cosmological ParametersNov 21 2003The galaxy power spectrum is now a well-known tool of precision cosmology. In addition to the overall shape, baryon oscillations and the small-scale suppression of power by massive neutrinos capture complimentary information on cosmological parameters ... More
Polarized CMB: Reionization and Primordial Tensor modesNov 03 2003We discuss upcoming opportunities with cosmic microwave background (CMB) observations during the post-WMAP era. The curl-modes of CMB polarization probe inflationary gravitational waves (IGWs). While a significant source of confusion is expected from ... More
After Acoustic Peaks: What's Next in CMB?Mar 04 2002Apr 04 2002The advent of high signal-to-noise cosmic microwave background (CMB) anisotropy experiments has allowed detailed studies on the power spectrum of temperature fluctuations. The existence of acoustic oscillations in the anisotropy power spectrum is now ... More
The integrated Sachs-Wolfe Effect -- Large Scale Structure CorrelationDec 17 2001We discuss the correlation between late-time integrated Sachs-Wolfe (ISW) effect in the cosmic microwave background (CMB) temperature anisotropies and the large scale structure of the local universe. This correlation has been proposed and studied in the ... More
Primordial Gravitational Waves and Inflation: CMB and Direct Detection With Space-Based Laser InterferometersMar 05 2005The curl-modes of Cosmic Microwave Background (CMB) polarization probe horizon-scale primordial gravitational waves related to inflation. A significant source of confusion is expected from a lensing conversion of polarization related to density perturbations ... More
Baryon Oscillations in the Large Scale StructureDec 18 2001We study the possibility for an observational detection of oscillations due to baryons in the matter power spectrum and suggest a new cosmological test using the angular power spectrum of halos. The "standard rulers" of the proposed test involve overall ... More
Squared temperature-temperature power spectrum as a probe of the CMB bispectrumMay 23 2001It is now well known that mode-coupling effects associated with certain secondary effects generate higher order correlations in cosmic microwave background (CMB) temperature anisotropies, beyond the two-point function. In order to extract the non-Gaussian ... More
Non-Gaussian Aspects of Thermal and Kinetic Sunyaev-Zel'dovich EffectsMay 03 2001We discuss non-Gaussian effects associated with the local large-scale structure contributions to the Cosmic Microwave Background (CMB) anisotropies through the thermal Sunyaev-Zel'dovich (SZ) effect. The non-Gaussianities associated with the SZ effect ... More
Gravitational Lens Image Separations versus Redshift as a Cosmological TestNov 17 1997Jan 15 2001This preprint, or a revised version, was never published as it was based on and included unacknowledged material from Helbig, P. (1997) `The Delta theta-z_s relation as a cosmological test', first presented at the 12th Potsdam Cosmology Workshop (V. M"uller, ... More
Halo Model at Its Best: Constraints on Conditional Luminosity Functions from Measured Galaxy StatisticsSep 01 2005Oct 18 2005(Summary) Using the conditional luminosity function (CLF) -- the luminosity distribution of galaxies in a dark matter halo -- as the fundamental building block, we present an empirical model for the galaxy distribution. The model predictions are compared ... More
A Brighter Past: Galaxy Luminosity Function At High RedshiftsJun 04 2005Aug 30 2005Using the conditional luminosity function -- the luminosity distribution of galaxies in a dark matter halo as a function of the halo mass -- we present an empirical model to describe the redshift evolution of the rest B-band galaxy luminosity function ... More
A Divided Universe: Red and Blue Galaxies and their Preferred EnvironmentsMay 20 2005May 22 2005(Summary) Making use of scaling relations between the central and the total galaxy luminosity of a dark matter halo as a function of the halo mass, and the scatter in these relations, we present an empirical model to describe the luminosity function (LF) ... More
21-cm Background Anisotropies Can Discern Primordial Non-GaussianityOct 09 2006Nov 23 2006The non-Gaussianity of initial perturbations provides information on the mechanism that generated primordial density fluctuations. The expected non-Gaussianity for slow-roll inflationary models is well below the ultimate detection level with cosmic microwave ... More
Weak Lensing Probes of the Galaxy-Mass Cross Power SpectrumJun 04 2002The angular correlation function of the background shear-foreground galaxy distribution probes the three dimensional cross power spectrum between mass and galaxies. The same cross power spectrum is also probed when foreground galaxy distribution is cross-correlated ... More
A Lensing Reconstruction of Primordial Cosmic Microwave Background PolarizationMay 17 2002We discuss a possibility to directly reconstruct the CMB polarization field at the last scattering surface by accounting for modifications imposed by the gravitational lensing effect. The suggested method requires a tracer field of the large scale structure ... More
Large Scale Structure in an Era of Precision CMB MeasurementsApr 04 2002Apr 06 2002The advent of high signal-to-noise cosmic microwave background (CMB) anisotropy experiments now allow detailed studies on the statistics related to temperature fluctuations. The existence of acoustic oscillations in the anisotropy power spectrum is now ... More
Large-Scale Non-Gaussianities in the 21 cm Background Anisotropies From the Era of ReionizationNov 16 2004The brightness temperature fluctuations in the 21 cm background related to neutral Hydrogen distribution provide a probe of physics related to the era of reionization when the intergalactic medium changed from a completely neutral to a partially ionized ... More
Gravitational Wave Background of Neutron Star-White Dwarf BinariesJun 21 2004We discuss the stochastic background of gravitational waves from ultra compact neutron star-white dwarf (NS-WD) binaries at cosmological distances. Under the assumption that accreting neutron stars and donor white dwarf stars form most of the low mass ... More
Second Moment of Halo Occupation NumberJun 22 2002The halo approach to large scale structure provides a physically motivated model to understand clustering properties of galaxies. An important aspect of the halo model involves a description on how galaxies populate dark matter halos or what is now called ... More
Second Order Corrections to Large Scale Structure Weak Lensing: Background Source ClusteringFeb 25 2002We discuss the second order contributions to lensing statistics resulting from the clustering of background sources from which galaxy shape measurements are made in weak lensing experiments. In addition to a previously discussed contribution to the lensing ... More
How Can We Study the Local Universe with CMB Photons?Dec 18 2001We show how observations of temperature fluctuations in cosmic microwave background (CMB) can be used to extract information related to the large scale structure, including dark matter distribution, pressure and halo velocities involving the line of sight, ... More
Second Order Corrections to Weak Lensing by Large-Scale StructureFeb 22 2002We calculate corrections to the power spectrum predictions of weak lensing by large scale structure due to higher order effects in the gravitational potential. Using a perturbative approach to third order in transverse displacements, we calculate a second ... More
The extragalactic background light from the measurements of the attenuation of high-energy gamma-ray spectrumMay 22 2013Jun 26 2013The attenuation of high-energy gamma-ray spectrum due to the electron-positron pair production against the extragalactic background light (EBL) provides an indirect method to measure the EBL of the universe. We use the measurements of the absorption features ... More
Intensity Mapping of Lyman-alpha Emission During the Epoch of ReionizationMay 07 2012Dec 13 2012We calculate the absolute intensity and anisotropies of the Lyman-alpha radiation field present during the epoch of reionization. We consider emission from both galaxies and the intergalactic medium (IGM) and take into account the main contributions to ... More
Polarization Signals of the 21 cm Background from the Era of ReionizationAug 17 2004While emission and absorption lines of the 21 cm spin-flip transition of neutral Hydrogen are intrinsically unpolarized, a magnetic field creates left- and right-handed polarized components through the Zeeman effect. Here we consider the resulting polarization ... More
Free-Free Emission at Low Radio FrequenciesFeb 10 2004We discuss free-free radio emission from ionized gas in the intergalactic medium. Because the emissivity is proportional to the square of the electron density, the mean background is strongly sensitive to the spatial clumping of free electrons. Using ... More
Halo Models of Large Scale StructureJun 28 2002We review the formalism and applications of the halo-based description of nonlinear gravitational clustering. In this approach, all mass is associated with virialized dark matter halos; models of the number and spatial distribution of the halos, and the ... More
Uncorrelated Estimates of Dark Energy EvolutionApr 02 2004Type Ia supernova data have recently become strong enough to enable, for the first time, constraints on the time variation of the dark energy density and its equation of state. Most analyses, however, are using simple two or three-parameter descriptions ... More
The Warm Spitzer Mission: Prospects for Studies of the Distant UniverseSep 06 2007IRAC excels at detecting distant objects. Due to a combination of the shapes of the spectral energy distributions of galaxies and the low background achieved from space, IRAC reaches greater depth in comparable exposure time at 3.6 and 4.5 micron than ... More
Future weak lensing constraints in a dark coupled universeApr 04 2011Coupled cosmologies can predict values for the cosmological parameters at low redshifts which may differ substantially from the parameters values within non-interacting cosmologies. Therefore, low redshift probes, as the growth of structure and the dark ... More
Amplitudes of thermal and kinetic Sunyaev-Zel'dovich signals from small-scale CMB anisotropiesMar 15 2011Feb 29 2012While the arcminute-scale Cosmic Microwave Background (CMB) anisotropies are due to secondary effects, point sources dominate the total anisotropy power spectrum. At high frequencies the point sources are primarily in the form of dusty, star-forming galaxies. ... More
Weak Lensing of the CMB: Extraction of Lensing Information from the TrispectrumApr 03 2002We discuss the four-point correlation function, or the trispectrum in Fourier space, of CMB temperature and polarization anisotropies due to the weak gravitational lensing effect by intervening large scale structure. We discuss the squared temperature ... More
New Approaches to Probing Minkowski FunctionalsNov 23 2010Jun 26 2013We generalize the concept of the ordinary skew-spectrum to probe the effect of non-Gaussianity on the morphology of Cosmic Microwave Background (CMB) maps in several domains: in real-space (where they are commonly known as cumulant-correlators), and in ... More
Kinetic Sunyaev-Zel'dovich effect from halo rotationJul 28 2001Mar 11 2002We discuss the kinetic Sunyaev-Zel'dovich (SZ) contribution to cosmic microwave background (CMB) temperature fluctuations due to coherent rotational velocity component of electrons within halos. This effect produces a distinct dipole-like temperature ... More
Searching for primordial black hole dark matter with pulsar timing arraysFeb 21 2007We discuss the possibility of detecting the presence of primordial black holes (PBHs), such as those that might account for galactic dark matter, using modification of pulsar timing residuals when PBHs pass within ~1000 AU and impart impulse accelerations ... More
Can LISA Resolve Distance to the Large Magellanic Cloud?Feb 23 2005The Laser Interferometer Space Antenna (LISA) is expected to detect N ~ 22 [x10^(+/- 1)] close white dwarf binaries in the Large Magellanic Cloud (LMC) through their gravitational radiation with signal-to-noise ratios greater than 10 in observational ... More
Anisotropy Studies of the Unresolved Far-infrared BackgroundMar 22 2007Aug 27 2007Dusty, starforming galaxies and active galactic nuclei that contribute to the integrated background intensity at far-infrared wavelengths trace the large-scale structure. Below the point source detection limit, correlations in the large-scale structure ... More
Where are the z=4 Lyman Break Galaxies? Results from Conditional Luminosity Function Models of Luminosity-dependent Correlation FunctionsApr 21 2006Using the conditional luminosity function (CLF) -- the luminosity distribution of galaxies in a dark matter halo -- as a way to model galaxy statistics, we study how z=4 Lyman Break Galaxies (LBGs) are distributed in dark matter halos. For this purpose, ... More
What is L*?: Anatomy of the Galaxy Luminosity FunctionApr 27 2005May 02 2005Using the empirical relations between the central galaxy luminosity and the halo mass, and between the total galaxy luminosity in a halo and the halo mass, we construct the galaxy luminosity function (LF). To the luminosity of the central galaxy in a ... More
First Sources in Infrared Light: Stars, Supernovae and MiniquasarsApr 05 2004May 10 2004The cosmic infrared background (IRB) at wavelengths between 1 micron and 3 microns provides a useful probe of early star-formation prior to and during reionization. To explain the high optical depth to electron scattering, as measured by the Wilkinson ... More