Hiranya V. Peiris
A5003176673- Cosmology and Gravitation Theories
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Dark Matter and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Stellar, planetary, and galactic studies
- Black Holes and Theoretical Physics
- Astrophysics and Cosmic Phenomena
- Scientific Research and Discoveries
- Pulsars and Gravitational Waves Research
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Particle physics theoretical and experimental studies
- Cold Atom Physics and Bose-Einstein Condensates
- Relativity and Gravitational Theory
- Geomagnetism and Paleomagnetism Studies
- Astrophysical Phenomena and Observations
- Statistical and numerical algorithms
- Image and Signal Denoising Methods
- Computational Physics and Python Applications
- Adaptive optics and wavefront sensing
- Remote Sensing in Agriculture
- CCD and CMOS Imaging Sensors
Stockholm University
2016-2024
AlbaNova
2017-2024
University of Cambridge
2008-2024
University College London
2015-2024
Astronomy and Space
2016
NGC Aerospace (Canada)
2016
UCL Australia
2014-2015
Kavli Institute for Particle Astrophysics and Cosmology
2013-2014
University of California, Santa Barbara
2013
University of Guelph
2012
WMAP precision data enables accurate testing of cosmological models. We find that the emerging standard model cosmology, a flat Lambda-dominated universe seeded by nearly scale-invariant adiabatic Gaussian fluctuations, fits data. With parameters fixed only data, we can fit finer scale CMB measurements and large scle structure (galaxy surveys Lyman alpha forest). This simple is also consistent with host other astronomical measurements. then to combination experiments (ACBAR CBI), 2dFGRS...
A simple cosmological model with only six parameters (matter density, Ωmh2, baryon Ωbh2, Hubble constant, H0, amplitude of fluctuations, σ8, optical depth, τ, and a slope for the scalar perturbation spectrum, ns) fits not 3 year WMAP temperature polarization data, but also small-scale CMB light element abundances, large-scale structure observations, supernova luminosity/distance relationship. Using data only, best-fit values power-law flat Λ cold dark matter (ΛCDM) are (Ωmh2,Ωbh2,h,ns,τ,σ8)...
We present full sky microwave maps in five bands (23 to 94 GHz) from the WMAP first year survey. Calibration errors are <0.5% and low systematic error level is well specified. The 21 per mode l=658. temperature-polarization cross-power spectrum reveals both acoustic features a large angle correlation reionization. optical depth of reionization 0.17 +/- 0.04, which implies epoch 180+220-80 Myr (95% CL) after Big Bang at redshift 20+10-9 for range ionization scenarios. This early...
The Wilkinson Microwave Anisotropy Probe WMAP has mapped the entire sky in five frequency bands between 23 and 94 GHz with polarization sensitive radiometers. We present three-year full-sky maps of analyze them for foreground emission cosmological implications. These observations open up a new window understanding universe. observes significant levels polarized due to both Galactic synchrotron radiation thermal dust emission. least contaminated channel is at 61 GHz. Informed by model...
We confront predictions of inflationary scenarios with the WMAP data, in combination complementary small-scale CMB measurements and large-scale structure data. The detection a large-angle anti-correlation temperature--polarization cross-power spectrum is signature adiabatic superhorizon fluctuations at time decoupling. data are described by pure fluctuations: we place an upper limit on correlated CDM isocurvature component. Using constraints shape scalar power amplitude gravity waves,...
We present new full-sky temperature maps in five frequency bands from 23 to 94 GHz, based on the first three years of WMAP sky survey. The maps, which are consistent with first-year and more sensitive, incorporate improvements data processing made possible by additional a complete analysis polarization signal. These include refinements gain calibration beam response models. employ two forms multi-frequency separate astrophysical foreground signals CMB, each improves our analyses. First, we...
This overview paper describes the legacy prospect and discovery potential of Dark Energy Survey (DES) beyond cosmological studies, illustrating it with examples from DES early data.DES is using a wide-field camera (DECam) on 4 m Blanco Telescope in Chile to image 5000 sq deg sky five filters (grizY).
We describe our methodology for comparing the Wilkinson Microwave Anisotropy Probe (WMAP) measurements of cosmic microwave background (CMB) and other complementary data sets to theoretical models. The unprecedented quality WMAP tight constraints on cosmological parameters that are derived require a rigorous analysis so approximations made in modeling do not lead significant biases. use likelihood function characterize statistical properties sky. outline Monte Carlo Markov Chains explore...
We summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes physics inflation. focus on prospects for using CMB to differentiate various inflationary mechanisms. In particular, a detection primordial B‐mode would demonstrate that inflation occurred at very high energy scale, and inflaton traversed super‐Planckian distance in field space. explain how such or constraint illuminate aspects Planck scale. Moreover, can constrain scale‐dependence...
We present a new bound on the ultra-light axion (ULA) dark matter mass $m_\text{a}$, using Lyman-alpha forest to look for suppressed cosmic structure growth: 95% lower limit $m_\text{a} > 2 \times 10^{-20}\,\text{eV}$. This strongly disfavors ($> 99.7\%$ credibility) canonical ULA with $10^{-22}\,\text{eV} < m_\text{a} 10^{-21}\,\text{eV}$, motivated by string axiverse and solutions possible tensions in cold model. strengthen previous equivalent bounds about an order of magnitude....
The Hubble constant (H_{0}) estimated from the local Cepheid-supernova distance ladder is in 3-σ tension with value extrapolated cosmic microwave background (CMB) data assuming standard cosmological model. Whether this represents new physics or systematic effects subject of intense debate. Here, we investigate how new, independent H_{0} estimates can arbitrate tension, assessing whether measurements are consistent being derived same model using posterior predictive distribution (PPD). We...
We present the first constraints on cosmology from Dark Energy Survey (DES), using weak lensing measurements preliminary Science Verification (SV) data. use 139 square degrees of SV data, which is less than 3% full DES survey area. Using cosmic shear 2-point over three redshift bins we find ${\ensuremath{\sigma}}_{8}({\mathrm{\ensuremath{\Omega}}}_{\mathrm{m}}/0.3{)}^{0.5}=0.81\ifmmode\pm\else\textpm\fi{}0.06$ (68% confidence), after marginalizing 7 systematics parameters and 3 other...
We introduce redMaGiC, an automated algorithm for selecting Luminous Red Galaxies (LRGs). The was specifically developed to minimize photometric redshift uncertainties in large-scale structure studies. redMaGiC achieves this by self-training the color-cuts necessary produce a luminosity-thresholded LRG sample of constant comoving density. demonstrate that photozs are very nearly as accurate best machine-learning based methods, yet they require minimal spectroscopic training, do not suffer...
The CMB has distinct peaks in both its temperature angular power spectrum (TT) and temperature-polarization cross-power (TE). From the WMAP data we find first peak at l = 220.1 +- 0.8 with an amplitude of 74.7 0.5 microK; trough 411.7 3.5 41.0 second 546 10 48.8 0.9 microK. TE antipeak 137 9 a -35 microK^2, 329 19 105 18 microK^2. All uncertainties are 1 sigma include calibration beam errors. An intuition for how determine cosmological parameters may be gained by limiting one's attention to...
Models which accelerate the expansion of universe through addition a function Ricci scalar $f(R)$ leave characteristic signature in large-scale structure at Compton wavelength scale extra degree freedom. We search for such current cosmological data sets: WMAP cosmic microwave background (CMB) power spectrum, Supernovae Legacy Survey supernovae distance measures, Sloan Digital Sky luminous red galaxy and galaxy-CMB angular correlations. Because theoretical uncertainties nonlinear evolution...
COrE (Cosmic Origins Explorer) is a fourth-generation full-sky, microwave-band satellite recently proposed to ESA within Cosmic Vision 2015-2025. will provide maps of the microwave sky in polarization and temperature 15 frequency bands, ranging from 45 GHz 795 GHz, with an angular resolution 23 arcmin (45 GHz) 1.3 (795 sensitivities roughly 10 30 times better than PLANCK (depending on channel). The mission lead breakthrough science wide range areas, primordial cosmology galactic...
Recent results from the BICEP, Keck Array and Planck Collaborations demonstrate that Galactic foregrounds are an unavoidable obstacle in search for evidence of inflationary gravitational waves cosmic microwave background (CMB) polarization. Beyond foregrounds, effect lensing by intervening large-scale structure further obscures all but strongest signals permitted current data. With a plethora ongoing upcoming experiments aiming to measure these signatures, careful self-consistent...
A fundamental assumption in the standard model of cosmology is that Universe isotropic on large scales. Breaking this leads to a set solutions Einstein's field equations, known as Bianchi cosmologies, only subset which have ever been tested against data. For first time, we consider all degrees freedom these conduct general test isotropy using cosmic microwave background temperature and polarization data from Planck. vector mode (associated with vorticity), obtain limit anisotropic expansion...
We present photometric redshift estimates for galaxies used in the weak lensing analysis of Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based methods -- ANNZ2, BPZ calibrated against BCC-Ufig simulations, SkyNet, and TPZ are analysed. For training, calibration, testing these methods, we construct a catalogue spectroscopically confirmed matched DES SV The performance is evaluated spectroscopic catalogue, focusing on metrics relevant analyses, with...
We discuss the model selection problem for inflationary cosmology. couple ModeCode, a publicly-available numerical solver primordial perturbation spectra, to nested sampler MultiNest, in order efficiently compute Bayesian evidence. Particular attention is paid specification of physically realistic priors, including parametrization post-inflationary expansion and associated thermalization scale. It confirmed that while present-day data tightly constrains properties power spectrum, it cannot...
Abstract We present a multi-messenger measurement of the Hubble constant H 0 using binary–black-hole merger GW170814 as standard siren, combined with photometric redshift catalog from Dark Energy Survey (DES). The luminosity distance is obtained gravitational wave signal detected by Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and information provided DES Year 3 data. Black hole mergers such are expected to lack bright...
We measure the cross-correlation between galaxy density in Dark Energy Survey (DES) Science Verification data and lensing of cosmic microwave background (CMB) as reconstructed with Planck satellite South Pole Telescope (SPT). When using DES main sample over full redshift range 0.2 < zphot 1.2, a signal is detected at 6σ 4σ SPT , respectively. then divide galaxies into five photometric bins, finding significant (>2σ) detections all bins. Comparing to fiducial cosmology, we find evolution...
The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky over ten years repeated observation. However, exactly how LSST observations be taken (the observing strategy or "cadence") not yet finalized. In this dynamically-evolving community white paper, we explore detailed performance anticipated science expected depend on small changes strategy. Using...
We derive robust constraints on primordial non-Gaussianity (PNG) using the clustering of 800,000 photometric quasars from Sloan Digital Sky Survey in redshift range $0.5<z<3.5$. These measurements rely novel technique {\it extended mode projection} to control impact spatially-varying systematics a fashion, making use blind analysis techniques. This allows accurate measurement quasar halo bias at largest scales, while discarding as little possible data. The standard local-type PNG parameters...