ORCID Profile
0000-0001-9110-5550
Current Organisation
The University of Edinburgh
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Publisher: Oxford University Press (OUP)
Date: 19-02-2020
Abstract: Accurate modelling of non-linear scales in galaxy clustering will be crucial for data analysis of Stage IV galaxy surveys. A selection of competing non-linear models must be made based on validation studies. We provide a comprehensive set of forecasts of two different models for the halo redshift space power spectrum, namely the commonly applied TNS model and an effective field theory of large-scale structure (EFTofLSS) inspired model. Using simulation data and a least-χ2 analysis, we determine ranges of validity for the models. We then conduct an exploratory Fisher analysis using the full anisotropic power spectrum to investigate parameter degeneracies. We proceed to perform an MCMC analysis utilizing the monopole, quadrupole, and hexadecapole spectra, with a restricted range of scales for the latter in order to avoid biasing our growth rate, f, constraint. We find that the TNS model with a Lorentzian d ing and standard Eulerian perturbative modelling outperforms other variants of the TNS model. Our MCMC analysis finds that the EFTofLSS-based model may provide tighter marginalized constraints on f at z = 0.5 and z = 1 than the TNS model, despite having additional nuisance parameters. However this depends on the range of scales used as well as the fiducial values and priors on the EFT nuisance parameters. Finally, we extend previous work to provide a consistent comparison between the Fisher matrix and MCMC forecasts using the multipole expansion formalism, and find good agreement between them.
Publisher: Oxford University Press (OUP)
Date: 11-07-2019
Abstract: The future of precision cosmology could benefit from cross-correlations between intensity maps of unresolved neutral hydrogen (H i) and more conventional optical galaxy surveys. A major challenge that needs to be overcome is removing the 21cm foreground emission that contaminates the cosmological H i signal. Using N-body simulations, we simulate H i intensity maps and optical catalogues that share the same underlying cosmology. Adding simulated foreground contamination and using state-of-the-art reconstruction techniques, we investigate the impacts that 21cm foregrounds and other systematics have on these cross-correlations. We find that the impact a Fast Independent Component Analysis 21cm foreground clean has on the cross-correlations with spectroscopic optical surveys with well-constrained redshifts is minimal. However, problems arise when photometric surveys are considered: We find that a redshift uncertainty σz ≥ 0.04 causes significant degradation in the cross-power spectrum signal. We diagnose the main root of these problems, which relates to arbitrary litude changes along the line of sight in the intensity maps caused by the foreground clean and suggest solutions that should be applicable to real data. These solutions involve a reconstruction of the line-of-sight temperature means using the available overlapping optical data along with an artificial extension to the H i data through redshift to address edge effects. We then put these solutions through a further test in a mock experiment that uses a clustering-based redshift estimation technique to constrain the photometric redshifts of the optical s le. We find that with our suggested reconstruction, cross-correlations can be utilized to make an accurate prediction of the optical redshift distribution.
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2019.51
Abstract: We present a detailed overview of the cosmological surveys that we aim to carry out with Phase 1 of the Square Kilometre Array (SKA1) and the science that they will enable. We highlight three main surveys: a medium-deep continuum weak lensing and low-redshift spectroscopic HI galaxy survey over 5 000 deg 2 a wide and deep continuum galaxy and HI intensity mapping (IM) survey over 20 000 deg 2 from $z = 0.35$ to 3 and a deep, high-redshift HI IM survey over 100 deg 2 from $z = 3$ to 6. Taken together, these surveys will achieve an array of important scientific goals: measuring the equation of state of dark energy out to $z \\sim 3$ with percent-level precision measurements of the cosmic expansion rate constraining possible deviations from General Relativity on cosmological scales by measuring the growth rate of structure through multiple independent methods mapping the structure of the Universe on the largest accessible scales, thus constraining fundamental properties such as isotropy, homogeneity, and non-Gaussianity and measuring the HI density and bias out to $z = 6$ . These surveys will also provide highly complementary clustering and weak lensing measurements that have independent systematic uncertainties to those of optical and near-infrared (NIR) surveys like Euclid , LSST, and WFIRST leading to a multitude of synergies that can improve constraints significantly beyond what optical or radio surveys can achieve on their own. This document, the 2018 Red Book , provides reference technical specifications, cosmological parameter forecasts, and an overview of relevant systematic effects for the three key surveys and will be regularly updated by the Cosmology Science Working Group in the run up to start of operations and the Key Science Programme of SKA1.
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2019.42
Abstract: The Square Kilometre Array (SKA) is a planned large radio interferometer designed to operate over a wide range of frequencies, and with an order of magnitude greater sensitivity and survey speed than any current radio telescope. The SKA will address many important topics in astronomy, ranging from planet formation to distant galaxies. However, in this work, we consider the perspective of the SKA as a facility for studying physics. We review four areas in which the SKA is expected to make major contributions to our understanding of fundamental physics: cosmic dawn and reionisation gravity and gravitational radiation cosmology and dark energy and dark matter and astroparticle physics. These discussions demonstrate that the SKA will be a spectacular physics machine, which will provide many new breakthroughs and novel insights on matter, energy, and spacetime.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Alkistis Pourtsidou.