Kai-Feng Chen

Massachusetts Institute of Technology

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Hilton Swarts

South African Radio Astronomy Observatory

Jacqueline N. Hewitt

Massachusetts Institute of Technology

M. F. Morales

University of Washington

Peter Sims

Arizona State University

Mathakane Molewa

South African Radio Astronomy Observatory

B. J. Hazelton

University of Washington

Cresshim Malgas

South African Radio Astronomy Observatory

Nico Eksteen

South African Radio Astronomy Observatory

Philip Bull

University of the Western Cape

Lourence Malan

South African Radio Astronomy Observatory

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University of California, Berkeley

South African Radio Astronomy Observatory

National Radio Astronomy Observatory

Arizona State University

Massachusetts Institute of Technology

University of Cambridge

The University of Tokyo

University of Washington

Kavli Institute for the Physics and Mathematics of the Universe

University of Pennsylvania

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matvis: A matrix-based visibility simulator for fast forward modelling of many-element 21 cm arrays

arXiv (Cornell University) (2023)

Piyanat Kittiwisit Steven Murray Hugh Garsden Philip Bull Christopher Cain

Detection of the faint 21 cm line emission from the Cosmic Dawn and Epoch of Reionisation will require not only exquisite control over instrumental calibration and systematics to achieve the necessary dynamic range of observations but also validation of analysis techniques to demonstrate their statistical properties and signal loss characteristics. A key ingredient in achieving this is the ability to perform high-fidelity simulations of the kinds of data that are produced by the large, many-element, radio interferometric arrays that have been purpose-built for these studies. The large scale of these arrays presents a computational challenge, as one must simulate a detailed sky and instrumental model across many hundreds of frequency channels, thousands of time samples, and tens of thousands of baselines for arrays with hundreds of antennas. In this paper, we present a fast matrix-based method for simulating radio interferometric measurements (visibilities) at the necessary scale. We achieve this through judicious use of primary beam interpolation, fast approximations for coordinate transforms, and a vectorised outer product to expand per-antenna quantities to per-baseline visibilities, coupled with standard parallelisation techniques. We validate the results of this method, implemented in the publicly-available matvis code, against a high-precision reference simulator, and explore its computational scaling on a variety of problems.

Interpolation

Visibility

Code (set theory)

10.48550/arxiv.2312.09763

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A Systematic Search of Distant Superclusters with the Subaru Hyper Suprime-Cam Survey

The Astrophysical Journal (2024)

Tsung-Chi Chen Yen‐Ting Lin Hsi-Yu Schive Masamune Oguri Kai-Feng Chen

Abstract Superclusters, encompassing environments across a wide range of overdensities, can be regarded as unique laboratories for studying galaxy evolution. Although numerous supercluster catalogs have been published, none of them goes beyond redshift z = 0.7. In this work, we adopt a physically motivated supercluster definition, requiring that superclusters should eventually collapse even in the presence of dark energy. Applying a friends-of-friends (FoF) algorithm to the CAMIRA cluster sample constructed using the Subaru Hyper Suprime-Cam survey data, we have conducted the first systematic search for superclusters at z = 0.5–1.0 and identified 673 supercluster candidates over an area of 1027 deg 2 . The FoF algorithm is calibrated by evolving N -body simulations to the far future to ensure high purity. We found that these high- z superclusters are mainly composed of two to four clusters, suggesting the limit of gravitationally bound structures in the younger Universe. In addition, we studied the properties of the clusters and brightest cluster galaxies (BCGs) residing in different large-scale environments. We found that clusters associated with superclusters are typically richer, but no apparent dependence of the BCG properties on large-scale structures is found. We also compared the abundance of observed superclusters with mock superclusters extracted from halo light cones, finding that photometric redshift uncertainty is a limiting factor in the performance of superclusters detection.

Supercluster (genetic)

10.3847/1538-4357/ad76ad

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Direct Optimal Mapping Image Power Spectrum and its Window Functions

The Astrophysical Journal (2024)

Zhilei Xu Honggeun Kim Jacqueline N. Hewitt Kai-Feng Chen Nicholas S. Kern

Abstract The key to detecting neutral hydrogen during the epoch of reionization (EoR) is to separate the cosmological signal from the dominating foreground radiation. We developed direct optimal mapping (DOM) to map interferometric visibilities; it contains only linear operations, with full knowledge of point spread functions from visibilities to images. Here, we demonstrate a fast Fourier transform-based image power spectrum and its window functions computed from the DOM images. We use noiseless simulation, based on the Hydrogen Epoch of Reionization Array Phase I configuration, to study the image power spectrum properties. The window functions show <10 −11 of the integrated power leaks from the foreground-dominated region into the EoR window; the 2D and 1D power spectra also verify the separation between the foregrounds and the EoR.

Window function

10.3847/1538-4357/ad528c

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