Prospects for clustering and lensing measurements with forthcoming intensity mapping and optical surveys
11 Jun 2016-Monthly Notices of the Royal Astronomical Society (Oxford University Press)-Vol. 459, Iss: 1, pp 863-870
TL;DR: In this article, the authors explore the potential of using intensity mapping surveys (MeerKAT, SKA) and optical galaxy surveys (DES, LSST) to detect HI clustering and weak gravitational lensing of 21cm emission in auto- and cross-correlation.
Abstract: We explore the potential of using intensity mapping surveys (MeerKAT, SKA) and optical galaxy surveys (DES, LSST) to detect HI clustering and weak gravitational lensing of 21cm emission in auto- and cross-correlation. Our forecasts show that high precision measurements of the clustering and lensing signals can be made in the near future using the intensity mapping technique. Such studies can be used to test the intensity mapping method, and constrain parameters such as the HI density $\Omega_{\rm HI}$, the HI bias $b_{\rm HI}$ and the galaxy-HI correlation coefficient $r_{\rm HI-g}$.
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University of Cape Town1, University of California, Berkeley2, University of Turin3, University of Western Australia4, University of Toronto5, ETH Zurich6, Imperial College London7, University of Barcelona8, University of Oslo9, Peking University10, University of the Western Cape11, Aix-Marseille University12, University of Portsmouth13, Tel Aviv University14, University of Amsterdam15, University of Sydney16, University of Geneva17, University of Hamburg18, University of Ferrara19, Centre national de la recherche scientifique20, Complutense University of Madrid21, Queen Mary University of London22, California Institute of Technology23, University of Padua24, University of Manchester25, Korea Astronomy and Space Science Institute26, Purple Mountain Observatory27, University of KwaZulu-Natal28, The University of Texas Rio Grande Valley29, Curtin University30, University of Queensland31, University of Zurich32, Uppsala University33, King's College London34, University of Bologna35, University of the Basque Country36, Huazhong University of Science and Technology37, University of Melbourne38, Guangzhou University39
TL;DR: 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 as mentioned in this paper.
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.
223 citations
University of Manchester1, Queen Mary University of London2, University of Oxford3, Korea Astronomy and Space Science Institute4, University of the Western Cape5, University of Melbourne6, University College London7, University of Barcelona8, University of Geneva9, Imperial College London10, Chinese Academy of Sciences11, University of Portsmouth12, University of Queensland13, ASTRON14, ETH Zurich15, Uppsala University16, Bielefeld University17, International School for Advanced Studies18, Kanagawa University19, University of Edinburgh20
TL;DR: 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 can be found in this paper.
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 deg2; a wide and deep continuum galaxy and HI intensity mapping (IM) survey over 20 000 deg2 from $z = 0.35$ to 3; and a deep, high-redshift HI IM survey over 100 deg2 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.
209 citations
Posted Content•
23 Sep 2007TL;DR: Here it is shown how the study of acoustic oscillation in the 21 cm brightness can be accomplished by economical three-dimensional intensity mapping, and may be the starting point for a new class of dark energy experiments dedicated to large angular scale mapping of the radio sky, shedding light on dark energy.
Abstract: The expansion of the universe appears to be accelerating, and the mysterious anti-gravity agent of this acceleration has been called ``dark energy''. To measure the dynamics of dark energy, Baryon Acoustic Oscillations (BAO) can be used. Previous discussions of the BAO dark energy test have focused on direct measurements of redshifts of as many as $10^9$ individual galaxies, by observing the 21cm line or by detecting optical emission. Here we show how the study of acoustic oscillation in the 21 cm brightness can be accomplished by economical three dimensional intensity mapping. If our estimates gain acceptance they may be the starting point for a new class of dark energy experiments dedicated to large angular scale mapping of the radio sky, shedding light on dark energy.
191 citations
TL;DR: In this article, the authors demonstrate a new method to constrain gravity on the largest cosmological scales by combining measurements of cosmic microwave background (CMB) lensing and the galaxy velocity field.
Abstract: We demonstrate a new method to constrain gravity on the largest cosmological scales by combining measurements of cosmic microwave background (CMB) lensing and the galaxy velocity field. $E_G$ is a statistic, constructed from a gravitational lensing tracer and a measure of velocities such as redshift-space distortions (RSD), that can discriminate between gravity models while being independent of clustering bias and $\sigma_8$. While traditionally, the lensing field for $E_G$ has been probed through galaxy lensing, CMB lensing has been proposed as a more robust tracer of the lensing field for $E_G$ at higher redshifts while avoiding intrinsic alignments. We perform the largest-scale measurement of $E_G$ ever, up to 150 Mpc/$h$, by cross-correlating the Planck CMB lensing map with the Sloan Digital Sky Survey III (SDSS-III) CMASS galaxy sample and combining this with our measurement of the CMASS auto-power spectrum and the RSD parameter $\beta$. We report $E_G(z=0.57)=0.243\pm0.060$ (stat) $\pm0.013$ (sys), a measurement in tension with the general relativity prediction at a level of 2.6$\sigma$. Note that our $E_G$ measurement deviates from GR only at scales greater than 80 Mpc/$h$, scales which have not been probed by previous $E_G$ tests. Upcoming surveys, which will provide an order-of-magnitude reduction in statistical errors, can significantly constrain alternative gravity models when combined with better control of systematics.
78 citations
Cites background from "Prospects for clustering and lensin..."
...In addition, it has been predicted (Pourtsidou et al. 2016) that the Square Kilometre Array2 could measure the galaxy–lensing cross-correlation from intensity mapping with high precision and at multiple source redshifts....
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TL;DR: In this article, the Square Kilometre Array (SKA) will carry out several wide and deep surveys of resolved and unresolved neutral hydrogen (HI) 21cm line-emitting galaxies, mapping a significant fraction of the sky from 0 to 6.
Abstract: Tests of general relativity (GR) are still in their infancy on cosmological scales, but forthcoming experiments promise to greatly improve their precision over a wide range of distance scales and redshifts. One such experiment, the Square Kilometre Array (SKA), will carry out several wide and deep surveys of resolved and unresolved neutral hydrogen (HI) 21cm line-emitting galaxies, mapping a significant fraction of the sky from $0 \le z \lesssim 6$. I present forecasts for the ability of a suite of possible SKA HI surveys to detect deviations from GR by reconstructing the cosmic expansion and growth history. SKA Phase 1 intensity mapping surveys can achieve sub-1\% measurements of $f\sigma_8$ out to $z\approx 1$, with an SKA1-MID Band 2 survey out to $z \lesssim 0.6$ able to surpass contemporary spectroscopic galaxy surveys such as DESI and Euclid in terms of constraints on modified gravity parameters if challenges such as foreground contamination can be tackled effectively. A more futuristic Phase 2 HI survey of $\sim10^9$ spectroscopic galaxy redshifts would be capable of detecting a $\sim 2\%$ modification of the Poisson equation out to $z\approx 2$.
63 citations
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TL;DR: In this paper, the authors present the results of a large library of cosmological N-body simulations, using power-law initial spectra, for the first order cosmologies.
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2,072 citations
TL;DR: In this article, the authors present the results of a large library of cosmological N-body simulations, using power-law initial spectra, showing that, when transformed under the self-similarity scaling, the scale-free spectra define a nonlinear locus that is clearly shallower than would be required under stable clustering.
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TL;DR: This review is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission and discusses five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis.
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768 citations
Additional excerpts
...The lensing convergence power spectrum from sources at redshift zs is given by the expression (Kaiser 1992, 1998) Cκκ(`) = 9Ω2mH 3 0 4c3 ∫ zs 0 dz Pδδ(k = `/χ, z) a2H(z)/H0 [ χ̂s − χ χ̂s ]2 , (16) with χ̂s ≡ χ(zs)....
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657 citations