Philip Bull
A5019247098- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Irish and British Studies
- Antenna Design and Optimization
- Radio Wave Propagation Studies
- Superconducting and THz Device Technology
- Scientific Research and Discoveries
- History and Developments in Astronomy
- Electromagnetic Compatibility and Measurements
- Dark Matter and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Particle Accelerators and Free-Electron Lasers
- Soil Moisture and Remote Sensing
- Gamma-ray bursts and supernovae
- Millimeter-Wave Propagation and Modeling
- Geophysics and Gravity Measurements
- Context-Aware Activity Recognition Systems
- Black Holes and Theoretical Physics
- Telecommunications and Broadcasting Technologies
- IoT and Edge/Fog Computing
University of the Western Cape
2018-2025
University of Manchester
2018-2025
Winona State University
2024
Queen Mary University of London
2019-2023
University of California, Berkeley
2018-2020
Ashford Hospital
2019
University of KwaZulu-Natal
2018
Jet Propulsion Laboratory
2016-2018
University of Oxford
2012-2018
Rhodes University
2018
We present a framework for forecasting cosmological constraints from future neutral hydrogen intensity mapping experiments at low to intermediate redshifts. In the process, we establish simple way of comparing such surveys with optical galaxy redshift surveys. explore wide range experimental configurations and assess how well number observables (the expansion rate, growth angular diameter distance) parameters densities dark energy matter, spatial curvature, equation state, etc.) will be...
Abstract We present a detailed overview of the cosmological surveys that we aim to carry out with Phase 1 Square Kilometre Array (SKA1) and science they will enable. highlight three main surveys: medium-deep continuum weak lensing low-redshift spectroscopic HI galaxy survey over 5 000 deg 2 ; wide deep intensity mapping (IM) 20 from $z = 0.35$ 3; deep, high-redshift IM 100 3$ 6. Taken together, these achieve an array important scientific goals: measuring equation state dark energy \sim...
Following the first two annual intensity mapping workshops at Stanford in March 2016 and Johns Hopkins June 2017, we report on recent advances theory, instrumentation observation that were presented these meetings some of opportunities challenges identified looking forward. With preliminary detections CO, [CII], Lya low-redshift 21cm, a host experiments set to go online next few years, field is rapidly progressing all fronts, with great anticipation for flood new exciting results. This...
Abstract We report upper limits on the Epoch of Reionization 21 cm power spectrum at redshifts 7.9 and 10.4 with 18 nights data (∼36 hr integration) from Phase I Hydrogen Array (HERA). The show evidence for systematics that can be largely suppressed systematic models down to a dynamic range ∼10 9 respect peak foreground power. This yields 95% confidence limit <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi...
Abstract Recently, the Hydrogen Epoch of Reionization Array (HERA) has produced experiment’s first upper limits on power spectrum 21 cm fluctuations at z ∼ 8 and 10. Here, we use several independent theoretical models to infer constraints intergalactic medium (IGM) galaxies during epoch reionization from these limits. We find that IGM must have been heated above adiabatic-cooling threshold by 8, uncertainties about ionization radio background. Combining HERA with complementary observations...
Abstract We report the most sensitive upper limits to date on 21 cm epoch of reionization power spectrum using 94 nights observing with Phase I Hydrogen Epoch Reionization Array (HERA). Using similar analysis techniques as in previously reported limits, we find at 95% confidence that Δ 2 ( k = 0.34 h Mpc −1 ) ≤ 457 mK z 7.9 and 0.36 3496 10.4, an improvement by a factor 2.1 2.6, respectively. These are mostly consistent thermal noise over wide range after our data quality cuts, despite...
HI intensity mapping (IM) is a novel technique capable of the large-scale structure Universe in three dimensions and delivering exquisite constraints on cosmology, by using as biased tracer dark matter density field.This achieved measuring redshifted 21cm line over sky range redshifts without requirement to resolve individual galaxies.In this chapter, we investigate potential SKA1 deliver maps broad frequencies substantial fraction sky.By pinning down baryon acoustic oscillation redshift...
We make use of a large set fast simulations an intensity mapping experiment with characteristics similar to those expected the Square Kilometre Array (SKA) in order study viability and limits blind foreground subtraction techniques. In particular, we consider different approaches: polynomial fitting, principal component analysis (PCA) independent (ICA). review motivations algorithms for three methods, show that they can all be described, using same mathematical framework, as approaches...
Abstract The Square Kilometre Array (SKA) is a planned large radio interferometer designed to operate over wide range of frequencies, and with an order magnitude greater sensitivity survey speed than any current telescope. SKA will address many important topics in astronomy, ranging from planet formation distant galaxies. However, this work, we consider the perspective as facility for studying physics. We review four areas which expected make major contributions our understanding fundamental...
Future surveys of large-scale structure will be able to measure perturbations on the scale cosmological horizon, and so could potentially probe a number novel relativistic effects that are negligibly small sub-horizon scales. These leave distinctive signatures in power spectra clustering observables and, if measurable, would open new window cosmology. We quantify size detectability for most relevant future experiments: spectroscopic photometric galaxy redshift surveys, intensity mapping...
While most purpose-built 21cm intensity mapping experiments are close-packed interferometer arrays, general-purpose dish arrays should also be capable of measuring the cosmological signal. This can achieved efficiently if array is used as a collection scanning autocorrelation dishes rather than an interferometer. As first step towards demonstrating feasibility this observing strategy, we show that able to successfully calibrate dual-polarisation data from 64 MeerKAT in L-band (856-1712 MHz,...
We present a detection of correlated clustering between MeerKAT radio intensity maps and galaxies from the WiggleZ Dark Energy Survey. find $7.7\sigma$ cross-correlation power spectrum, amplitude which is proportional to product HI density fraction ($\Omega_{\rm HI}$), bias ($b_{\rm HI}$) coefficient ($r$). therefore obtain constraint $\Omega_{\rm HI} b_{\rm r\,{=}\,[0.86\,{\pm}\,0.10\,({\rm stat})\,{\pm}\,0.12\,({\rm sys})]\,{\times}\,10^{-3}$, at an effective scale $k_{\rm...
Abstract This paper presents the design and deployment of Hydrogen Epoch Reionization Array (HERA) phase II system. HERA is designed as a staged experiment targeting 21 cm emission measurements Reionization. First results from I array are published early 2022, system nearing completion. We describe discuss progress on commissioning future upgrades. As designated Square Kilometre pathfinder instrument, we also show number “case studies” that investigate systematics seen while system, which...
The apparent accelerating expansion of the Universe, determined from observations distant supernovae, and often taken to imply existence dark energy, may alternatively be explained by effects a giant underdense void if we relax assumption homogeneity on large scales. Recent studies have made use spherically symmetric, radially inhomogeneous Lema\^{\i}tre-Tolman-Bondi (LTB) models derive strong constraints this scenario, particularly kinematic Sunyaev-Zel'dovich effect which is sensitive...
The Square Kilometre Array (SKA) will conduct the biggest spectroscopic galaxy survey ever, by detecting 21cm emission line of neutral hydrogen (HI) from around a billion galaxies over 3/4 sky, out to redshift z~2. This allow redshift-space matter power spectrum, and corresponding dark energy observables, be measured with unprecedented precision. In this paper, we present an improved model HI number counts bias semi-analytic simulations, use it calculate expected yield surveys variety Phase...
We discuss the ground-breaking science that will be possible with a wide area survey, using MeerKAT telescope, known as MeerKLASS (MeerKAT Large Area Synoptic Survey). The current specifications of make it great fit for applications require large survey speeds but not necessarily high angular resolutions. In particular, cosmology, over $\sim 4,000 \, {\rm deg}^2$ 4,000$ hours potentially provide first ever measurements baryon acoustic oscillations 21cm intensity mapping technique, enough...
This white paper envisions a revolutionary post-DESI, post-LSST dark energy program based on intensity mapping of the redshifted 21cm emission line from neutral hydrogen at radio frequencies. The proposed survey has unique capability to quadruple volume Universe surveyed by optical programs, provide percent-level measurement expansion history $z \sim 6$, open window explore physics beyond concordance $Λ$CDM model, and significantly improve precision standard cosmological parameters. In...
We investigate the signatures left by massive neutrinos on spatial distribution of neutral hydrogen (HI) in post-reionization era running hydrodynamic simulations that include as additional collisionless particles.We find halos massive/massless neutrino cosmologies host a similar amount hydrogen, although for fixed halo mass, average, HI mass increases with sum masses.Our results show is more strongly clustered neutrinos, while its abundance, Ω (z), lower.These effects arise mainly from...
The Core Cosmology Library (CCL) provides routines to compute basic cosmological observables a high degree of accuracy, which have been verified with an extensive suite validation tests. Predictions are provided for many quantities, including distances, angular power spectra, correlation functions, halo bias and the mass function through state-of-the-art modeling prescriptions available in literature. Fiducial specifications expected galaxy distributions Large Synoptic Survey Telescope...
We present a study of internal reflection and cross coupling systematics in Phase I the Hydrogen Epoch Reionization Array (HERA). In companion paper, we outlined mathematical formalism for such presented algorithms modeling removing them from data. this work, apply these techniques to data HERA's first observing season as method demonstration. The show evidence that, without removal, would hinder detection 21 cm power spectrum targeted EoR line-of-sight modes range 0.2 < k_parallel 0.5\ h^-1...
Our current understanding of the Universe is established through pristine measurements structure in cosmic microwave background (CMB) and distribution shapes galaxies tracing large scale (LSS) Universe. One key ingredient that underlies cosmological observables field sources observed assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps most robust theoretical prediction models explain Universe; itis necessarily present even...
Inflation may provide unique insight into the physics at highest available energy scales that cannot be replicated in any realistic terrestrial experiment. Features primordial power spectrum are generically predicted a wide class of models inflation and its alternatives, observationally one most overlooked channels for finding evidence non-minimal inflationary models. Constraints from observations cosmic microwave background cover widest range feature frequencies, but sensitive constraints...
Blind cleaning methods are currently the preferred strategy for handling foreground contamination in single-dish HI intensity mapping surveys. Despite increasing sophistication of blind techniques, some signal loss will be inevitable across all scales. Constructing a corrective transfer function using mock injection into contaminated data has been practice relied on experiments. However, assessing whether this approach is viable future surveys where precision cosmology aim, remains...
Outflows promote the escape of Lyman-α (Lyα) photons from dusty interstellar media. The process radiative transfer through outflows is often modeled by a spherically symmetric, geometrically thin shell neutral gas that scatters emitted central Lyα source. Despite its simplified geometry, this "shell model" has been surprisingly successful at reproducing observed line shapes. In paper, we perform automated fitting on set noisy simulated shell-model spectra in order to determine whether...