ORCID Profile
0000-0002-0394-0896
Current Organisation
Swinburne University of Technology
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Astronomical sciences | Data mining and knowledge discovery | Machine learning not elsewhere classified | Cosmology and extragalactic astronomy |
Publisher: Oxford University Press (OUP)
Date: 21-02-2018
DOI: 10.1093/MNRAS/STY453
Publisher: Oxford University Press (OUP)
Date: 21-11-2022
Abstract: The theoretical basis of dark energy remains unknown and could signify a need to modify the laws of gravity on cosmological scales. In this study, we investigate how the clustering and motions of galaxies can be used as probes of modified gravity theories, using galaxy and direct peculiar velocity auto- and cross-correlation functions. We measure and fit these correlation functions in simulations of ΛCDM, DGP, and f(R) cosmologies and, by extracting the characteristic parameters of each model, we show that these theories can be distinguished from General Relativity (GR) using these measurements. We present forecasts showing that with sufficiently large data s les, this analysis technique is a competitive probe that can help place limits on allowed deviations from GR. For ex le, a peculiar velocity survey reaching to z = 0.5 with $20{{\ \rm per\ cent}}$ distance accuracy would constrain model parameters to 3-σ confidence limits log10|fR0| & −6.45 for f(R) gravity and $r_\mathrm{ c} \gt 2.88 \, \mathrm{ c}/H_0$ for nDGP, assuming a fiducial GR model.
Publisher: Oxford University Press (OUP)
Date: 26-11-2019
Publisher: arXiv
Date: 2022
Publisher: Oxford University Press (OUP)
Date: 21-08-2020
Abstract: Baryon acoustic oscillations (BAOs) represent one of the cleanest probes of dark energy, allowing for tests of the cosmological model through the measurement of distance and expansion rate from a 3D galaxy distribution. The signal appears at large scales in the correlation function where linear theory applies, allowing for the construction of accurate models. However, due to the lower number of modes available at these scales, s le variance has a significant impact on the signal, and may sharpen or widen the underlying peak. Therefore, equivalent mock realizations of a galaxy survey present different errors in the position of the peak when uncertainties are estimated from the posterior probability distribution corresponding to the in idual mocks. Hence, the posterior width, often quoted as the error in BAO survey measurements, is subject to s le noise. A different definition of the error is provided by the asymptotic variance of the maximum likelihood estimator, which involves the average over multiple realizations, and is not subject to s le noise. In this work, we reanalyse the main galaxy survey data available for BAO measurements and quantify the impact of the noise component on the error quoted for BAO measurements. We quantify the difference between three definitions of the error: the confidence region computed from a single posterior, the average of the variances of many realizations, and the Fisher matrix prediction assuming a Gaussian likelihood. We also explore the impact of a ‘detectability prior’ based on the significance of the BAO detection.
Publisher: IOP Publishing
Date: 05-03-2018
Publisher: Oxford University Press (OUP)
Date: 11-10-2017
Publisher: American Astronomical Society
Date: 20-10-2022
Abstract: The Dark Energy Spectroscopic Instrument (DESI) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3.°2 diameter prime-focus corrector a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0.″1 and a median signal-to-noise ratio of 7 of the [O ii ] doublet at 8 × 10 −17 erg s −1 cm −2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned.
Publisher: American Physical Society (APS)
Date: 28-04-2021
Publisher: Oxford University Press (OUP)
Date: 25-01-2021
Abstract: We present an improved framework for estimating the growth rate of large-scale structure, using measurements of the galaxy–velocity cross-correlation in configuration space. We consider standard estimators of the velocity autocorrelation function, ψ1 and ψ2, the two-point galaxy correlation function, ξgg, and introduce a new estimator of the galaxy–velocity cross-correlation function, ψ3. By including pair counts measured from random catalogues of velocities and positions s led from distributions characteristic of the true data, we find that the variance in the galaxy–velocity cross-correlation function is significantly reduced. Applying a covariance analysis and χ2 minimization procedure to these statistics, we determine estimates and errors for the normalized growth rate fσ8 and the parameter β = f/b, where b is the galaxy bias factor. We test this framework on mock hemisphere data sets for redshift z & 0.1 with realistic velocity noise constructed from the l-picola simulation code, and find that we are able to recover the fiducial value of fσ8 from the joint combination of ψ1 + ψ2 + ψ3 + ξgg, with 15 per cent accuracy from in idual mocks. We also recover the fiducial fσ8 to within 1σ regardless of the combination of correlation statistics used. When we consider all four statistics together we find that the statistical uncertainty in our measurement of the growth rate is reduced by $59{{\\ \\rm per\\ cent}}$ compared to the same analysis only considering ψ2, by $53{{\\ \\rm per\\ cent}}$ compared to the same analysis only considering ψ1, and by $52{{\\ \\rm per\\ cent}}$ compared to the same analysis jointly considering ψ1 and ψ2.
Publisher: Oxford University Press (OUP)
Date: 11-04-2022
Abstract: We present measurements of the local primordial non-Gaussianity parameter $f_{\\mathrm{NL}}^\\mathrm{local} $from the clustering of 343 708 quasars with redshifts 0.8 & z & 2.2 distributed over 4808 deg2 from the final data release (DR16) of the extended Baryon Acoustic Oscillation Spectroscopic Survey (eBOSS), the largest volume spectroscopic survey up to date. Our analysis is performed in Fourier space, using the power spectrum monopole at very large scales to constrain the scale-dependent halo bias. We demonstrate the robustness of our analysis pipeline with EZ-mock catalogues that simulate the eBOSS DR16 target selection. We carefully assess the impact of systematics on our measurement, exploiting a novel neural network scheme for cleaning the DR16 s le as well as test multiple contamination removal methods. We estimate the bias due to the overcorrection of the systematic removal to be sub-dominant compared to the statistical uncertainty. We find fNL = −12 ± 21 (68 per cent confidence) for the main clustering s le including quasars with redshifts between 0.8 and 2.2, after applying redshift weighting techniques, designed for non-Gaussianity measurement from large scales structure, to optimize our analysis, which improve our results by 37 per cent.
Publisher: Oxford University Press (OUP)
Date: 24-07-2018
Publisher: American Astronomical Society
Date: 29-06-2017
Publisher: Oxford University Press (OUP)
Date: 06-06-2023
Abstract: Combining different observational probes, such as galaxy clustering and weak lensing, is a promising technique for unveiling the physics of the Universe with upcoming dark energy experiments. The galaxy redshift s le from the Dark Energy Spectroscopic Instrument (DESI) will have a significant overlap with major ongoing imaging surveys specifically designed for weak lensing measurements: the Kilo-Degree Survey (KiDS), the Dark Energy Survey (DES) and the Hyper Suprime-Cam (HSC) survey. In this work, we analyse simulated redshift and lensing catalogues to establish a new strategy for combining high-quality cosmological imaging and spectroscopic data, in view of the first-year data assembly analysis of DESI. In a test case fitting for a reduced parameter set, we employ an optimal data compression scheme able to identify those aspects of the data that are most sensitive to cosmological information and lify them with respect to other aspects of the data. We find this optimal compression approach is able to preserve all the information related to the growth of structures.
Publisher: Oxford University Press (OUP)
Date: 10-03-2018
DOI: 10.1093/MNRAS/STY654
Abstract: We present a measurement of the anisotropic and isotropic Baryon Acoustic Oscillations (BAO) from the extended Baryon Oscillation Spectroscopic Survey Data Release 14 quasar s le with optimal redshift weights. Applying the redshift weights improves the constraint on the BAO dilation parameter α(zeff) by 17 per cent. We reconstruct the evolution history of the BAO distance indicators in the redshift range of 0.8 & z & 2.2. This paper is part of a set that analyses the eBOSS DR14 quasar s le.
Publisher: IOP Publishing
Date: 03-09-2019
Publisher: Oxford University Press (OUP)
Date: 12-11-2022
Abstract: Galaxy peculiar velocities provide an integral source of cosmological information that can be harnessed to measure the growth rate of large-scale structure and constrain possible extensions to General Relativity. In this work, we present a method for extracting the information contained within galaxy peculiar velocities through an ensemble of direct peculiar velocity and galaxy clustering correlation statistics, including the effects of redshift space distortions, using data from the 6-degree Field Galaxy Survey. Our method compares the auto- and cross-correlation function multipoles of these observables, with respect to the local line of sight, with the predictions of cosmological models. We find that the uncertainty in our measurement is improved when combining these two sources of information in comparison to fitting to either peculiar velocity or clustering information separately. When combining velocity and density statistics in the range $27 \\lt s \\lt 123 \\, h^{-1}$ Mpc we obtain a value for the local growth rate of fσ8 = 0.358 ± 0.075 and for the linear redshift distortion parameter β = 0.298 ± 0.065, recovering both with 20.9 per cent and 21.8 per cent accuracy, respectively. We conclude this work by comparing our measurement with other recent local measurements of the growth rate, spanning different data sets and methodologies. We find that our results are in broad agreement with those in the literature and are fully consistent with ΛCDM cosmology. Our methods can be readily scaled to analyse upcoming large galaxy surveys and achieve accurate tests of the cosmological model.
Publisher: Oxford University Press (OUP)
Date: 21-08-2020
Abstract: Combining different observational probes, such as galaxy clustering and weak lensing, is a promising technique for unveiling the physics of the Universe with upcoming dark energy experiments. Whilst this strategy significantly improves parameter constraints, decreasing the degeneracies of in idual analyses and controlling the systematics, processing data from tens of millions of galaxies is not a trivial task. In this work, we derive and test a new compressed statistic for joint clustering and lensing data analysis, maximizing the scientific return and decreasing the computational cost. Our approach compresses the data by up-weighting the components most sensitive to the parameters of interest, with no loss of information, taking into account information from the cross-correlation between the two probes. We derive optimal redshift weights which may be applied to in idual galaxies when testing a given statistic and cosmological model.
Publisher: Oxford University Press (OUP)
Date: 23-09-2017
Publisher: Oxford University Press (OUP)
Date: 04-08-2015
Publisher: Oxford University Press (OUP)
Date: 26-10-2018
Publisher: Oxford University Press (OUP)
Date: 23-07-2201
Publisher: Oxford University Press (OUP)
Date: 24-02-2018
DOI: 10.1093/MNRAS/STY506
Publisher: Oxford University Press (OUP)
Date: 20-12-2018
Publisher: Oxford University Press (OUP)
Date: 20-12-2019
Start Date: 2024
End Date: 12-2026
Amount: $444,000.00
Funder: Australian Research Council
View Funded Activity