Danny C. Price

Bayesian constraints on the global 21-cm signal from the Cosmic Dawn

The birth of the first luminous sources and the ensuing epoch of reionization are best studied via the redshifted 21-cm emission line, the signature of the first two imprinting the last. In this work we present a fully-Bayesian method, HIBAYES, for extracting the faint, global (sky-averaged) 21-cm signal from the much brighter foreground emission. We show that a simplified (but plausible), Gaussian model of the 21-cm emission from the Cosmic Dawn epoch (15 . z . 30), parameterized by an amplitudeAHI, a frequency peak HI and a width HI, can be extracted even in the presence of a structured foreground frequency spectrum (parameterized as a 7 th -order polynomial), provided sufficient signal-to-noise (400 hours of observation with a single dipole). We apply our method to an early, 19-minute long observation from the Large aperture Experiment to detect the Dark Ages, constraining the 21-cm signal amplitude and width to be 890 6:5 MHz (corresponding to z > 1:9 at redshift z’ 20) respectively at the 95-per-cent confidence level in the range 13:2 > 50 MHz).

Generalized formalisms of the radio interferometer measurement equation

The Radio Interferometer Measurement Equation (RIME) is a matrix-based mathematical model that describes the response of a radio interferometer. The Jones calculus it employs is not suitable for describing the analogue components of a telescope. This is because it does not consider the effect of impedance mismatches between components. This paper aims to highlight the limitations of Jones calculus, and suggests some alternative methods that are more applicable. We reformulate the RIME with a different basis that includes magnetic and mixed coherency statistics. We present a microwave network inspired 2N-port version of the RIME, and a tensor formalism based upon the electromagnetic tensor from special relativity. We elucidate the limitations of the Jones-matrix-based RIME for describing analogue components. We show how measured scattering parameters of analogue components can be used in a 2N-port version of the RIME. In addition, we show how motion at relativistic speed affects the observed flux. We present reformulations of the RIME that correctly account for magnetic field coherency. These reformulations extend the standard formulation, highlight its limitations, and may have applications in space-based interferometry and precise absolute calibration experiments.

A Simultaneous Search for Prompt Radio Emission Associated with the Short GRB 170112A Using the All-sky Imaging Capability of the OVRO-LWA

We have conducted the most sensitive low frequency (below 100 MHz) search to date for prompt, low-frequency radio emission associated with short-duration gamma-ray bursts (GRBs), using the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA). The OVRO-LWAs nearly full-hemisphere field-of-view (

Bifrost: A Python/C++ Framework for High-Throughput Stream Processing in Astronomy

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Introduction to the Special Issue on Digital Signal Processing in Radio Astronomy

,

Digital Signal Processing using Stream High Performance Computing: A 512-input Broadband Correlator for Radio Astronomy

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A SCALABLE HYBRID FPGA/GPU FX CORRELATOR

square degrees) allows us to search for low-frequency (sub-

Design and characterization of the Large-aperture Experiment to Detect the Dark Age (LEDA) radiometer systems

100

Spectrometers and Polyphase Filterbanks in Radio Astronomy

MHz) counterparts for a large sample of the subset of GRB events for which prompt radio emission has been predicted. Following the detection of short GRB 170112A by Swift, we used all-sky OVRO-LWA images spanning one hour prior to and two hours following the GRB event to search for a transient source coincident with the position of GRB 170112A. We detect no transient source, with our most constraining

Optimizing performance-per-watt on GPUs in high performance computing

1\sigma