HI intensity mapping with MeerKAT: Calibration pipeline for multi-dish autocorrelation observations
Jingying Wang, Mario G. Santos, Philip Bull, Keith Grainge, Steven Cunnington, Jose Fonseca, Melis O. Irfan, Yichao Li, Alkistis Pourtsidou, Paula S. Soares, Ma… 展开作者
Jingying Wang, Mario G. Santos, Philip Bull, Keith Grainge, Steven Cunnington, Jose Fonseca, Melis O. Irfan, Yichao Li, Alkistis Pourtsidou, Paula S. Soares, Marta Spinelli, Gianni Bernardi, Brandon Engelbrecht
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24 pages, 34 figures, accepted for publication in MNRAS
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.
Single-dish HI Intensity Mapping with the SKAO: Precursor Progress with MeerKAT's Large Area Synoptic Survey (MeerKLASS)
University of Portsmouth（朴茨茅斯大学）；The University of Manchester（曼彻斯特大学）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；University of the Western Cape（西开普敦大学）；Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；The University of Edinburgh（爱丁堡大学）；University of Cambridge（剑桥大学）；Northeastern University（东北大学）；Observatoire de la Côte d’Azur（蔚蓝海岸天文台）
Upcoming and future neutral hydrogen Intensity Mapping surveys offer a great opportunity to constrain cosmology in the post-reionization Universe, provided a good accuracy is achieved in the separation between the strong foregrounds and the cosmological signal. Cleaning methods rely on the frequency smoothness of the foregrounds and are often applied under the assumption of a simplistic Gaussian primary beam. In this work, we test the cleaning in the presence of a realistic primary beam model with a non trivial frequency dependence. We focus on the Square Kilometre Array precursor MeerKAT tele…
The MeerKAT (64 x 13.5m dish radio interferometer) is South Africa's precursor instrument for the Square Kilometre Array (SKA), exploring dish design, instrumentation, and the characteristics of a Karoo desert site and is projected to be on sky in 2016. One of two top-priority, Key Projects is a single deep field, integrating for 5000 hours total with the aim to detect neutral atomic hydrogen through its 21 cm line emission out to redshift unity and beyond. This first truly deep HI survey will help constrain fueling models for galaxy assembly and evolution. It will measure the evolution of the…
We present a detection of correlated clustering between MeerKAT radio intensity maps and galaxies from the WiggleZ Dark Energy Survey. We find a $7.7σ$ detection of the cross-correlation power spectrum, the amplitude of which is proportional to the product of the HI density fraction ($Ω_{\rm HI}$), HI bias ($b_{\rm HI}$) and the cross-correlation coefficient ($r$). We therefore obtain the constraint $Ω_{\rm HI} b_{\rm HI} r\,{=}\,[0.86\,{\pm}\,0.10\,({\rm stat})\,{\pm}\,0.12\,({\rm sys})]\,{\times}\,10^{-3}$, at an effective scale of $k_{\rm eff}\,{\sim}\,0.13\,h\,{\rm Mpc}^{-1}$. The intensit…
Revealing cosmological fluctuations in 21cm intensity maps with MeerKLASS: from maps to power spectra
University of Portsmouth（朴茨茅斯大学）；The University of Manchester（曼彻斯特大学）；Università degli Studi di Milano（米兰大学）；INFN – Istituto Nazionale di Fisica Nucleare（意大利国家核物理研究所）；INAF – Istituto Nazionale di Astrofisica（意大利国家天体物理研究所）；Università degli Studi di Torino（都灵大学）；Instituto de Física de Cantabria (IFCA), CSIC-Univ. de Cantabria（坎塔布里亚物理研究所（CSIC-坎塔布里亚大学））；Department of Physics & Astronomy, University of the Western Cape（西开普大学物理与天文系）
The nature of the time correlated noise component (the 1/f noise) of single dish radio telescopes is critical to the detectability of the HI signal in intensity mapping experiments. In this paper, we present the 1/f noise properties of the MeerKAT receiver system using South Celestial Pole (SCP) tracking data. We estimate both the temporal power spectrum density and the 2D power spectrum density for each of the antennas and polarizations. We apply Singular Value Decomposition (SVD) to the dataset and show that, by removing the strongest components, the 1/f noise can be drastically reduced, ind…
Intensity mapping (IM) with neutral hydrogen is a promising avenue to probe the large scale structure of the Universe. In this paper, we demonstrate that using the 64-dish MeerKAT radio telescope as a connected interferometer, it is possible to make a statistical detection of HI in the post-reionization Universe. With the MIGHTEE (MeerKAT International GHz Tiered Extragalactic Exploration) survey project observing in the L-band ($856 < ν< 1712$ MHz, $z < 0.66$), we can achieve the required sensitivity to measure the HI IM power spectrum on quasi-linear scales, which will provide an important c…
Cosmological Prediction from the joint observation of MeerKAT and CSST at $z$ = 0.4 $\sim$ 1.2
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences(UCAS)（中国科学院大学天文与空间科学学院）；Department of Physics, Stellenbosch University（斯泰伦博斯大学物理系）；Science Center for Chinese Space Station Survey Telescope, National Astronomical Observatories, Chinese Academy of Science（中国科学院国家天文台中国空间站巡天望远镜科学中心）
The high dynamic range between contaminating foreground emission and the fluctuating 21cm brightness temperature field is one of the most problematic characteristics of 21cm intensity mapping data. While these components would ordinarily have distinctive frequency spectra, making it relatively easy to separate them, instrumental effects and calibration errors further complicate matters by modulating and mixing them together. A popular class of foreground cleaning method are unsupervised techniques related to Principal Component Analysis (PCA), which exploit the different shapes and amplitudes …
We apply for the first time Gaussian Process Regression (GPR) as a foreground removal technique in the context of single-dish, low redshift HI intensity mapping, and present an open-source Python toolkit for doing so. We use MeerKAT and SKA1-MID-like simulations of 21cm foregrounds (including polarisation leakage), HI cosmological signal and instrumental noise. We find that it is possible to use GPR as a foreground removal technique in this context, and that it is better suited in some cases to recover the HI power spectrum than Principal Component Analysis (PCA), especially on small scales. G…
The bispectrum is a 3-point statistic with the potential to provide additional information beyond power spectra analyses of survey datasets. Radio telescopes which broadly survey the 21cm emission from neutral hydrogen (HI) are a promising way to probe LSS and in this work we present an investigation into the HI intensity mapping (IM) bispectrum using simulations. We present a model of the redshift space HI IM bispectrum including observational effects from the radio telescope beam and 21cm foreground contamination. We validate our modelling prescriptions with measurements from robust IM simul…
Upcoming cosmological intensity mapping surveys will open new windows on the Universe, but they must first overcome a number of significant systematic effects, including polarization leakage. We present a formalism that uses scan strategy information to model the effect of different instrumental systematics on the recovered cosmological intensity signal for `single-dish' (autocorrelation) surveys. This modelling classifies different systematics according to their spin symmetry, making it particularly relevant for dealing with polarization leakage. We show how to use this formalism to calculate…
Foreground removal in HI 21 cm intensity mapping under frequency-dependent beam distortions
Foundation for Research and Technology Hellas (FORTH)（希腊研究与技术基金会）；Université Paris-Saclay（巴黎萨克雷大学）；Université Paris Cité（巴黎西岱大学）；CEA（法国原子能和替代能源委员会）；CNRS（法国国家科学研究中心）；Observatoire de la Côte d’Azur（蔚蓝海岸天文台）；University of the Western Cape（西开普敦大学）；University of Crete（克里特大学）
meer21cm: an Analysis Pipeline and Comprehensive Toolkit for HI Intensity Mapping
The University of Edinburgh（爱丁堡大学）；University of Portsmouth（朴茨茅斯大学）；Jodrell Bank Centre for Astrophysics, Department of Physics & Astronomy, The University of Manchester（曼彻斯特大学物理与天文学系乔德雷尔银行天体物理学中心）；SISSA – International School for Advanced Studies（国际高等研究院）；Università degli Studi di Milano（米兰大学）；INFN – Istituto Nazionale di Fisica Nucleare, Sezione di Milano（意大利国家核物理研究所米兰分部）；INAF – Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Brera-Merate（意大利国家天体物理研究所布雷拉-梅拉特天文台）；Università degli Studi di Torino（都灵大学）
Methodological Frontiers in 21-cm Intensity Mapping: the Treatment of Systematics and Foreground Contamination
Observatoire de la Côte d’Azur（蔚蓝海岸天文台）；University of the Western Cape（西开普敦大学）；Indian Institute of Technology Kharagpur（印度理工学院卡拉格普尔分校）；Foundation for Research and Technology Hellas (FORTH)（希腊研究与技术基金会）；The University of Manchester（曼彻斯特大学）；The University of Edinburgh（爱丁堡大学）；Indian Institute of Technology Madras（印度理工学院马德拉斯分校）；ETH Zurich（苏黎世联邦理工学院）；University of Portsmouth（朴茨茅斯大学）；Banwarilal Bhalotia College（班瓦里拉尔·巴洛蒂亚学院）；University of Cambridge（剑桥大学）；Northeastern University（东北大学）；Chinese Academy of Sciences（中国科学院）
Neutral Hydrogen Intensity Mapping (HI IM) surveys will be a powerful new probe of cosmology. However, strong astrophysical foregrounds contaminate the signal and their coupling with instrumental systematics further increases the data cleaning complexity. In this work, we simulate a realistic single-dish HI IM survey of a $5000$~deg$^2$ patch in the $950 - 1400$ MHz range, with both the MID telescope of the SKA Observatory (SKAO) and MeerKAT, its precursor. We include a state-of-the-art HI simulations and explore different foreground models and instrumental effects such as non-homogeneous ther…
JESSNet: Joint dEconvolution and Sparse Separation Network for HI 21 cm foreground cleaning
Foundation for Research and Technology Hellas (FORTH)（希腊基金会）；Université Paris-Saclay（巴黎萨克雷大学）；Université Paris Cité（巴黎西岱大学）；CEA（法国原子能和替代能源委员会）；CNRS（法国国家科学研究中心）；University of Crete（克里特大学）；Observatoire de la Côte d’Azur（蔚蓝海岸天文台）；Laboratoire Lagrange（拉格朗日实验室）；University of the Western Cape（西开普大学）；Institute of Computer Science, Foundation for Research and Technology Hellas (FORTH)（希腊基金会计算机科学研究所）
