ORCID Profile
0000-0002-3287-2327
Current Organisation
University of California, Berkeley
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Publisher: American Astronomical Society
Date: 06-08-2018
Publisher: IOP Publishing
Date: 05-02-2018
Publisher: American Astronomical Society
Date: 19-02-2021
Publisher: American Astronomical Society
Date: 07-2021
Publisher: American Geophysical Union (AGU)
Date: 12-2022
DOI: 10.1029/2022RS007558
Abstract: Scattering from objects near an antenna produce correlated signals from strong compact radio sources in a manner similar to those used by the “Sea Interferometer” to measure the radio source positions using the fine frequency structure in the total power spectrum of a single antenna. These fringes or ripples due to correlated signal interference are present at a low level in the spectrum of any single antenna and are a major source of systematics in systems used to measure the global redshifted 21‐cm signal from the early universe. In the Sea Interferometer a single antenna on a cliff above the sea is used to add the signal from the direct path to the signal from the path reflected from the sea thereby forming an interferometer. This was used for mapping radio sources with a single antenna by Bolton and Slee in the 1950s. In this paper we derive analytic expressions to determine the level of these ripples and compare these results in a few simple cases with electromagnetic modeling software to verify that the analytic calculations are sufficient to obtain the magnitude of the scattering effects on the measurements of the global 21‐cm signal. These analytic calculations are needed to evaluate the magnitude of the effects in cases that are either too complex or take too much time to be modeled using software.
Publisher: Oxford University Press (OUP)
Date: 15-09-2022
Abstract: We develop a Bayesian model that jointly constrains receiver calibration, foregrounds, and cosmic 21 cm signal for the EDGES global 21 cm experiment. This model simultaneously describes calibration data taken in the lab along with sky-data taken with the EDGES low-band antenna. We apply our model to the same data (both sky and calibration) used to report evidence for the first star formation in 2018. We find that receiver calibration does not contribute a significant uncertainty to the inferred cosmic signal ($\\lt 1{{\\ \\rm per\\ cent}}$), though our joint model is able to more robustly estimate the cosmic signal for foreground models that are otherwise too inflexible to describe the sky data. We identify the presence of a significant systematic in the calibration data, which is largely avoided in our analysis, but must be examined more closely in future work. Our likelihood provides a foundation for future analyses in which other instrumental systematics, such as beam corrections and reflection parameters, may be added in a modular manner.
Publisher: Oxford University Press (OUP)
Date: 10-03-2023
Abstract: Accurately accounting for spectral structure in spectrometer data induced by instrumental chromaticity on scales relevant for detection of the 21-cm signal is among the most significant challenges in global 21-cm signal analysis. In the publicly available Experiment to Detect the Global Epoch of Reionization Signature low-band data set, this complicating structure is suppressed using beam-factor-based chromaticity correction (BFCC), which works by iding the data by a sky-map-weighted model of the spectral structure of the instrument beam. Several analyses of these data have employed models that start with the assumption that this correction is complete. However, while BFCC mitigates the impact of instrumental chromaticity on the data, given realistic assumptions regarding the spectral structure of the foregrounds, the correction is only partial. This complicates the interpretation of fits to the data with intrinsic sky models (models that assume no instrumental contribution to the spectral structure of the data). In this paper, we derive a BFCC data model from an analytical treatment of BFCC and demonstrate using simulated observations that, in contrast to using an intrinsic sky model for the data, the BFCC data model enables unbiased recovery of a simulated global 21-cm signal from beam-factor chromaticity-corrected data in the limit that the data are corrected with an error-free beam-factor model.
Location: United States of America
No related grants have been discovered for Raul Monsalve.