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MeerKLASS: MeerKAT Large Area Synoptic Survey

TL;DR: The MeerKLASS (MeerKAT Large Area Synoptic Survey) as mentioned in this paper is a large-scale survey of the sky that uses the Meer-KAT telescope.
Abstract: We discuss the ground-breaking science that will be possible with a wide area survey, using the MeerKAT telescope, known as MeerKLASS (MeerKAT Large Area Synoptic Survey). The current specifications of MeerKAT make it a great fit for science applications that require large survey speeds but not necessarily high angular resolutions. In particular, for cosmology, a large survey over $\sim 4,000 \, {\rm deg}^2$ for $\sim 4,000$ hours will potentially provide the first ever measurements of the baryon acoustic oscillations using the 21cm intensity mapping technique, with enough accuracy to impose constraints on the nature of dark energy. The combination with multi-wavelength data will give unique additional information, such as exquisite constraints on primordial non-Gaussianity using the multi-tracer technique, as well as a better handle on foregrounds and systematics. Such a wide survey with MeerKAT is also a great match for HI galaxy studies, providing unrivalled statistics in the pre-SKA era for galaxies resolved in the HI emission line beyond local structures at z > 0.01. It will also produce a large continuum galaxy sample down to a depth of about 5\,$\mu$Jy in L-band, which is quite unique over such large areas and will allow studies of the large-scale structure of the Universe out to high redshifts, complementing the galaxy HI survey to form a transformational multi-wavelength approach to study galaxy dynamics and evolution. Finally, the same survey will supply unique information for a range of other science applications, including a large statistical investigation of galaxy clusters as well as produce a rotation measure map across a huge swathe of the sky. The MeerKLASS survey will be a crucial step on the road to using SKA1-MID for cosmological applications and other commensal surveys, as described in the top priority SKA key science projects (abridged).
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TL;DR: In this paper, the authors report on the recent advances in theory, instrumentation and observation that were presented in these workshops and some of the opportunities and challenges that were identified looking forward.
Abstract: Following the first two annual intensity mapping workshops at Stanford in March 2016 and Johns Hopkins in June 2017, we report on the recent advances in theory, instrumentation and observation that were presented in these meetings and some of the opportunities and challenges that were identified looking forward. With preliminary detections of CO, [CII], Lya and low-redshift 21cm, and a host of experiments set to go online in the next few years, the field is rapidly progressing on all fronts, with great anticipation for a flood of new exciting results. This current snapshot provides an efficient reference for experts in related fields and a useful resource for nonspecialists. We begin by introducing the concept of line-intensity mapping and then discuss the broad array of science goals that will be enabled, ranging from the history of star formation, reionization and galaxy evolution to measuring baryon acoustic oscillations at high redshift and constraining theories of dark matter, modified gravity and dark energy. After reviewing the first detections reported to date, we survey the experimental landscape, presenting the parameters and capabilities of relevant instruments such as COMAP, mmIMe, AIM-CO, CCAT-p, TIME, CONCERTO, CHIME, HIRAX, HERA, STARFIRE, MeerKAT/SKA and SPHEREx. Finally, we describe recent theoretical advances: different approaches to modeling line luminosity functions, several techniques to separate the desired signal from foregrounds, statistical methods to analyze the data, and frameworks to generate realistic intensity map simulations.

134 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used the well-established, computationally efficient Santa Cruz semi-analytic model, with recently implemented multiphase gas partitioning and H2-based star formation recipes, to make predictions for a wide variety of galaxy properties for galaxy populations at 4-10.
Abstract: The long-anticipated James Webb Space Telescope (JWST) will be able to directly detect large samples of galaxies at very high redshift. Using the well-established, computationally efficient Santa Cruz semi-analytic model, with recently implemented multiphase gas partitioning and H2-based star formation recipes, we make predictions for a wide variety of galaxy properties for galaxy populations at $z$ = 4-10. In this work, we provide forecasts for the physical properties of high-redshift galaxies and links to their photometric properties. With physical parameters calibrated only to $z\sim0$ observations, our model predictions are in good agreement with current observational constraints on stellar mass and star formation rate distribution functions up to $z \sim 8$. We also provide predictions representing wide, deep, and lensed JWST survey configurations. We study the redshift evolution of key galaxy properties and the scaling relations among them. Taking advantage of our models' high computational efficiency, we study the impact of systematically varying the model parameters. All distribution functions and scaling relations presented in this work are available at this https URL.

75 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive framework for modeling the line-intensity mapping power spectrum, including redshift space distortions and the Alcock-Paczynski effect, is presented. But the power spectrum is not robust to cosmology and astrophysics at the same time.
Abstract: Line-intensity mapping (LIM) provides a promising way to probe cosmology, reionization and galaxy evolution. However, its sensitivity to cosmology and astrophysics at the same time is also a nuisance. Here we develop a comprehensive framework for modeling the LIM power spectrum, which includes redshift space distortions and the Alcock-Paczynski effect. We then identify and isolate degeneracies with astrophysics so that they can be marginalized over. We study the gains of using the multipole expansion of the anisotropic power spectrum, providing an accurate analytic expression for their covariance, and find a 10%--75% increase in the precision of the baryon acoustic oscillation scale measurements when including the hexadecapole in the analysis. We discuss different observational strategies when targeting other cosmological parameters, such as the sum of neutrino masses or primordial non-Gaussianity, finding that fewer and wider redshift bins are typically optimal. Overall, our formalism facilitates an optimal extraction of cosmological constraints robust to astrophysics.

61 citations

Journal ArticleDOI
TL;DR: In this article, the authors calibrate dual-polarization autocorrelation data from 64 MeerKAT dishes in the L-band (856-1712 MHz, 4096 channels) with 10.5 hours of data retained from six nights of observing.
Abstract: 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 21cm signal. This can be achieved most efficiently if the array is used as a collection of scanning autocorrelation dishes rather than as an interferometer. As a first step towards demonstrating the feasibility of this observing strategy, we show that we are able to successfully calibrate dual-polarisation autocorrelation data from 64 MeerKAT dishes in the L-band (856-1712 MHz, 4096 channels), with 10.5 hours of data retained from six nights of observing. We describe our calibration pipeline, which is based on multi-level RFI flagging, periodic noise diode injection to stabilise gain drifts and an absolute calibration based on a multi-component sky model. We show that it is sufficiently accurate to recover maps of diffuse celestial emission and point sources over a 10 deg x 30 deg patch of the sky overlapping with the WiggleZ 11hr field. The reconstructed maps have a good level of consistency between per-dish maps and external datasets, with the estimated thermal noise limited to 1.4 x the theoretical noise level (~ 2 mK). The residual maps have rms amplitudes below 0.1 K, corresponding to <1% of the model temperature. The reconstructed Galactic HI intensity map shows excellent agreement with the Effelsberg-Bonn HI Survey, and the flux of the radio galaxy 4C+03.18 is recovered to within 3.6%, which demonstrates that the autocorrelation can be successfully calibrated to give the zero-spacing flux and potentially help in the imaging of MeerKAT interferometric data. Our results provide a positive indication towards the feasibility of using MeerKAT and the future SKA to measure the HI intensity mapping signal and probe cosmology on degree scales and above.

45 citations


Cites background from "MeerKLASS: MeerKAT Large Area Synop..."

  • ...With SKA1 scheduled to begin full operations in 2028, there is a good window of opportunity for MeerKAT to robustly demonstrate the single-dish survey method and make a significant first detection before the SKA comes online (Santos et al. 2017)....

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Journal ArticleDOI
TL;DR: In this article, a forecast analysis for constraining local type non-Gaussianity and its two-parameter extension with a simple scale-dependence was performed, and the results showed that the combination of upcoming cosmological surveys could achieve a precision of 0.12$ (0.22) on the running index.
Abstract: Next-generation galaxy surveys will be able to measure perturbations on scales beyond the equality scale. On these ultra-large scales, primordial non-Gaussianity leaves signatures that can shed light on the mechanism by which perturbations in the early Universe are generated. We perform a forecast analysis for constraining local type non-Gaussianity and its two-parameter extension with a simple scale-dependence. We combine different clustering measurements from future galaxy surveys -- a 21cm intensity mapping survey and two photometric galaxy surveys -- via the multi-tracer approach. Furthermore we then include CMB lensing from a CMB Stage 4 experiment in the multi-tracer, which can improve the constraints on bias parameters. We forecast $\sigma(f_{\rm NL}) \simeq 0.9$ (1.4) by combining SKA1, a Euclid-like (LSST-like) survey, and CMB-S4 lensing. With CMB lensing, the precision on $f_{\rm NL}$ improves by up to a factor of 2, showing that a joint analysis is important. In the case with running of $f_{\rm NL}$, our results show that the combination of upcoming cosmological surveys could achieve $\sigma(n_{\rm NL}) \simeq 0.12$ (0.22) on the running index.

39 citations

References
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01 Jan 2015

315 citations


"MeerKLASS: MeerKAT Large Area Synop..." refers background or methods in this paper

  • ...The key example is SKA1-MID, the first phase of the SKA, to be set in South Africa, which will deliver competitive and transformational cosmology through a series of measurements using a large sky survey (Maartens et al. 2015; Santos et al. 2015; Jarvis et al. 2015; Abdalla et al. 2015)....

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  • ...We assumed a simple power law, MHI(M) = AMα, with α = 0.6 and A ∼ 220 both redshift independent and chosen to match the observed ΩHI at z = 0.8 (see Santos et al. 2015 for details)....

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  • ...Intensity mapping transfers the problem to one of foreground cleaning: how to develop cleaning methods to remove everything that is not the HI signal at a given frequency, which also impacts on the calibration requirements of the instrument (see Santos et al. 2015)....

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  • ...The noise properties of an intensity mapping survey like MeerKLASS have been described in detail in Santos et al. (2015); Pourtsidou et al. (2016b)....

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