Publications

LuSEE ’Night’: The Lunar Surface Electromagnetics Experiment

Anonymous — Tue, 24 Jan 2023 21:48:45 +0000

LuSEE ’Night’: The Lunar Surface Electromagnetics Experiment Anonymous (not verified) Tue, 01/24/2023 - 14:48

Authors: Stuart D. Bale, Neil Bassett, Jack O. Burns, Johnny Dorigo Jones, Keith Goetz, Christian Hellum-Bye, et al.

Abstract: The Lunar Surface Electromagnetics Explorer ’LuSEE Night’ is a low frequency radio astronomy experiment that will be delivered to the farside of the Moon by the NASA Commercial Lunar Payload Services (CLPS) program in late 2025 or early 2026. The payload system is being developed jointly by NASA and the US Department of Energy (DOE) and consists of a 4 channel, 50 MHz Nyquist baseband receiver system and 2 orthogonal ∼6m tip-to-tip electric dipole antennas. LuSEE Night will enjoy standalone operations through the lunar night, without the electromagnetic interference (EMI) of an operating lander system and antipodal to our noisy home planet. Read more via the arVix.

Stuart D. Bale, Neil Bassett, Jack O. Burns, Johnny Dorigo Jones, Keith Goetz, Christian Hellum-Bye, et al.

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Lost Horizon: Quantifying the Effect of Local Topography on Global 21-cm Cosmology Data Analysis

Anonymous — Thu, 03 Jun 2021 21:51:12 +0000

Lost Horizon: Quantifying the Effect of Local Topography on Global 21-cm Cosmology Data Analysis Anonymous (not verified) Thu, 06/03/2021 - 15:51

Authors: Neil Bassett, David Rapetti, Keith Tauscher, Bang D. Nhan, David D. Bordenave, Joshua J. Hibbard, Jack O. Burns

Abstract: We present an investigation of the horizon and its effect on global 21-cm observations and analysis. We find that the horizon cannot be ignored when modeling low frequency observations. Even if the sky and antenna beam are known exactly, forward models cannot fully describe the beam-weighted foreground component without accurate knowledge of the horizon. When fitting data to extract the 21-cm signal, a single time-averaged spectrum or independent multi-spectrum fits may be able to compensate for the bias imposed by the horizon. However, these types of fits lack constraining power on the 21-cm signal, leading to large uncertainties on the signal extraction, in some cases larger in magnitude than the 21-cm signal itself. A significant decrease in signal uncertainty can be achieved by performing multi-spectrum fits in which the spectra are modeled simultaneously with common parameters. The cost of this greatly increased constraining power, however, is that the time dependence of the horizon's effect, which is more complex than its spectral dependence, must be precisely modeled to achieve a good fit. To aid in modeling the horizon, we present an algorithm and Python package for calculating the horizon profile from a given observation site using elevation data. We also address several practical concerns such as pixelization error, uncertainty in the horizon profile, and foreground obstructions such as surrounding buildings and vegetation. We demonstrate that our training set-based analysis pipeline can account for all of these factors to model the horizon well enough to precisely extract the 21-cm signal from simulated observations. Read more via the arVix.

Neil Bassett, David Rapetti, Keith Tauscher, Bang D. Nhan, David D. Bordenave, Joshua J. Hibbard, Jack O. Burns

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Global 21-cm signal extraction from foreground and instrumental effects IV: Accounting for realistic instrument uncertainties and their overlap with foreground and signal models

Anonymous — Tue, 04 May 2021 21:48:30 +0000

Global 21-cm signal extraction from foreground and instrumental effects IV: Accounting for realistic instrument uncertainties and their overlap with foreground and signal models Anonymous (not verified) Tue, 05/04/2021 - 15:48

Authors: Keith Tauscher, David Rapetti, Bang D. Nhan, Alec Handy, Neil Bassett, Joshua Hibbard, David Bordenave, Richard F. Bradley, Jack O. Burns

Abstract: All 21-cm signal experiments rely on electronic receivers that affect the data via both multiplicative and additive biases through the receiver's gain and noise temperature. While experiments attempt to remove these biases, the residuals of their imperfect calibration techniques can still confuse signal extraction algorithms. In this paper, the fourth and final installment of our pipeline series, we present a technique for fitting out receiver effects as efficiently as possible. The fact that the gain and global signal, which are multiplied in the observation equation, must both be modeled implies that the model of the data is nonlinear in its parameters, making numerical sampling the only way to explore the parameter distribution rigorously. However, multi-spectra fits, which are necessary to extract the signal confidently as demonstrated in the third paper of the series, often require large numbers of foreground parameters, increasing the dimension of the posterior distribution that must be explored and therefore causing numerical sampling inefficiencies. Building upon techniques in the second paper of the series, we outline a method to explore the full parameter distribution by numerically sampling a small subset of the parameters and analytically marginalizing over the others. We test this method in simulation using a type-I Chebyshev band-pass filter gain model and a fast signal model based on a spline between local extrema. The method works efficiently, converging quickly to the posterior signal parameter distribution. The final signal uncertainties are of the same order as the noise in the data. Read more via the arVix.

Keith Tauscher, David Rapetti, Bang D. Nhan, Alec Handy, Neil Bassett, Joshua Hibbard, David Bordenave, Richard F. Bradley, Jack O. Burns

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A Lunar Farside Low Radio Frequency Array for Dark Ages 21-cm Cosmology

Anonymous — Mon, 15 Mar 2021 21:54:22 +0000

A Lunar Farside Low Radio Frequency Array for Dark Ages 21-cm Cosmology Anonymous (not verified) Mon, 03/15/2021 - 15:54

Authors: Jack Burns, Gregg Hallinan, Tzu-Ching Chang, Marin Anderson, Judd Bowman, Richard Bradley, Steven Furlanetto, Alex Hegedus, Justin Kasper, Jonathan Kocz, Joseph Lazio, Jim Lux, Robert MacDowall, Jordan Mirocha, Issa Nesnas, Jonathan Pober, Ronald Polidan, David Rapetti, Andres Romero-Wolf, Anže Slosar, Albert Stebbins, Lawrence Teitelbaum, Martin White

Abstract: An array of low-frequency dipole antennas on the lunar farside surface will probe a unique, unexplored epoch in the early Universe called the Dark Ages. It begins at Recombination when neutral hydrogen atoms formed, first revealed by the cosmic microwave background. This epoch is free of stars and astrophysics, so it is ideal to investigate high energy particle processes including dark matter, early Dark Energy, neutrinos, and cosmic strings. A NASA-funded study investigated the design of the instrument and the deployment strategy from a lander of 128 pairs of antenna dipoles across a 10 kmx10 km area on the lunar surface. The antenna nodes are tethered to the lander for central data processing, power, and data transmission to a relay satellite. The array, named FARSIDE, would provide the capability to image the entire sky in 1400 channels spanning frequencies from 100 kHz to 40 MHz, extending down two orders of magnitude below bands accessible to ground-based radio astronomy. The lunar farside can simultaneously provide isolation from terrestrial radio frequency interference, the Earth's auroral kilometric radiation, and plasma noise from the solar wind. It is thus the only location within the inner solar system from which sky noise limited observations can be carried out at sub-MHz frequencies. Through precision calibration via an orbiting beacon and exquisite foreground characterization, the farside array would measure the Dark Ages global 21-cm signal at redshifts z~35-200. It will also be a pathfinder for a larger 21-cm power spectrum instrument by carefully measuring the foreground with high dynamic range. Read more via the arVix.

Jack Burns, Gregg Hallinan, Tzu-Ching Chang, Marin Anderson, Judd Bowman, Richard Bradley, Steven Furlanetto, Alex Hegedus, Justin Kasper, Jonathan Kocz, Joseph Lazio, Jim Lux, Robert MacDowall, Jordan Mirocha, Issa Nesnas, Jonathan Pober, Ronald Polidan, David Rapetti, Andres Romero-Wolf, Anže Slosar, Albert Stebbins, Lawrence Teitelbaum, Martin White

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Low Radio Frequency Observations from the Moon Enabled by NASA Landed Payload Missions

Anonymous — Mon, 08 Mar 2021 22:30:03 +0000

Low Radio Frequency Observations from the Moon Enabled by NASA Landed Payload Missions Anonymous (not verified) Mon, 03/08/2021 - 15:30

Authors: Jack O. Burns, Robert MacDowall, Stuart Bale, Gregg Hallinan, Neil Bassett and Alex Hegedus

Abstract: A new era of exploration of the low radio frequency universe from the Moon will soon be underway with landed payload missions facilitated by NASA's Commercial Lunar Payload Services (CLPS) program. CLPS landers are scheduled to deliver two radio science experiments, Radio wave Observations at the Lunar Surface of the photoElectron Sheath (ROLSES) to the nearside and Lunar Surface Electromagnetics Experiment (LuSEE) to the farside, beginning in 2021. These instruments will be pathfinders for a 10 km diameter interferometric array, Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE), composed of 128 pairs of dipole antennas proposed to be delivered to the lunar surface later in the decade. ROLSES and LuSEE, operating at frequencies from ≈100 kHz to a few tens of megahertz, will investigate the plasma environment above the lunar surface and measure the fidelity of radio spectra on the surface. Both use electrically short, spiral-tube deployable antennas and radio spectrometers based upon previous flight models. ROLSES will measure the photoelectron sheath density to better understand the charging of the lunar surface via photoionization and impacts from the solar wind, charged dust, and current anthropogenic radio frequency interference. LuSEE will measure the local magnetic field and exo-ionospheric density, interplanetary radio bursts, Jovian and terrestrial natural radio emission, and the galactic synchrotron spectrum. FARSIDE, and its precursor risk-reduction six antenna-node array PRIME, would be the first radio interferometers on the Moon. FARSIDE would break new ground by imaging radio emission from coronal mass ejections (CME) beyond 2R⊙, monitor auroral radiation from the B-fields of Uranus and Neptune (not observed since Voyager), and detect radio emission from stellar CMEs and the magnetic fields of nearby potentially habitable exoplanets. Read the full paper on The Planetary Science Journal.

Jack O. Burns, Robert MacDowall, Stuart Bale, Gregg Hallinan, Neil Bassett and Alex Hegedus

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Global 21-cm Cosmology from the Farside of the Moon

Anonymous — Mon, 08 Mar 2021 22:00:23 +0000

Global 21-cm Cosmology from the Farside of the Moon Anonymous (not verified) Mon, 03/08/2021 - 15:00

Authors: Jack Burns, Stuart Bale, Richard Bradley, Z. Ahmed, S.W. Allen, J. Bowman, S. Furlanetto, R. MacDowall, J. Mirocha, B. Nhan, M. Pivovaroff, M. Pulupa, D. Rapetti, A. Slosar, K. Tauscher

Abstract: One of the last unexplored windows to the cosmos, the Dark Ages and Cosmic Dawn, can be opened using a simple low frequency radio telescope from the stable, quiet lunar farside to measure the Global 21-cm spectrum. This frontier remains an enormous gap in our knowledge of the Universe. Standard models of physics and cosmology are untested during this critical epoch. The messenger of information about this period is the 1420 MHz (21-cm) radiation from the hyperfine transition of neutral hydrogen, Doppler-shifted to low radio astronomy frequencies by the expansion of the Universe. The Global 21-cm spectrum uniquely probes the cosmological model during the Dark Ages plus the evolving astrophysics during Cosmic Dawn, yielding constraints on the first stars, on accreting black holes, and on exotic physics such as dark matter-baryon interactions. A single low frequency radio telescope can measure the Global spectrum between ~10-110 MHz because of the ubiquity of neutral hydrogen. Precise characterizations of the telescope and its surroundings are required to detect this weak, isotropic emission of hydrogen amidst the bright foreground Galactic radiation. We describe how two antennas will permit observations over the full frequency band: a pair of orthogonal wire antennas and a 0.3-m3 patch antenna. A four-channel correlation spectropolarimeter forms the core of the detector electronics. Technology challenges include advanced calibration techniques to disentangle covariances between a bright foreground and a weak 21-cm signal, using techniques similar to those for the CMB, thermal management for temperature swings of >250C, and efficient power to allow operations through a two-week lunar night. This simple telescope sets the stage for a lunar farside interferometric array to measure the Dark Ages power spectrum. Read more via the arVix.

Jack Burns, Stuart Bale, Richard Bradley, Z. Ahmed, S.W. Allen, J. Bowman, S. Furlanetto, R. MacDowall, J. Mirocha, B. Nhan, M. Pivovaroff, M. Pulupa, D. Rapetti, A. Slosar, K. Tauscher

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Validation of EDGES Low-Band Antenna Beam Model

Anonymous — Sun, 28 Feb 2021 21:44:23 +0000

Validation of EDGES Low-Band Antenna Beam Model Anonymous (not verified) Sun, 02/28/2021 - 14:44

Authors: Nivedita Mahesh, Judd D. Bowman, Thomas J. Mozdzen, Alan E. E. Rogers, Raul A. Monsalve, Steven G. Murray, David Lewis

Abstract: The response of the antenna is a source of uncertainty in measurements with the Experiment to Detect the Global EoR Signature (EDGES). We aim to validate the beam model of the low-band (50-100 MHz) dipole antenna with comparisons between models and against data. We find that simulations of a simplified model of the antenna over an infinite perfectly conducting ground plane are, with one exception, robust to changes of numerical electromagnetic solver code or algorithm. For simulations of the antenna with the actual finite ground plane and realistic soil properties, we find that two out of three numerical solvers agree well. Applying our analysis pipeline to a simulated driftscan observation from an early EDGES low-band instrument that had a 10 m × 10 m ground plane, we find residual levels after fitting and removing a five-term foreground model to data binned in Local Sidereal Time (LST) average about 250 mK with 40 mK variation between numerical solvers. A similar analysis of the primary 30 m × 30 m sawtooth ground plane reduced the LST-averaged residuals to about 90 mK with ± 10 mK between the two viable solvers. More broadly we show that larger ground planes generally perform better than smaller ground planes. Simulated data have a power which is within 4% of real observations, a limitation of net accuracy of the sky and beam models. We observe that residual spectral structures after foreground model fits match qualitatively between simulated data and observations, suggesting that the frequency dependence of the beam is reasonably represented by the models. We find that soil conductivity of 0.02 Sm −1 and relative permittivity of 3.5 yield good agreement between simulated spectra and observations. This is consistent with the soil properties reported by Sutinjo et al. (2015) for the Murchison Radio-astronomy Observatory, where EDGES is located. Read more via the arVix.

Nivedita Mahesh, Judd D. Bowman, Thomas J. Mozdzen, Alan E. E. Rogers, Raul A. Monsalve, Steven G. Murray, David Lewis

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Transformative Science from the Lunar Farside: Observations of the Dark Ages and Exoplanetary Systems at Low Radio Frequencies

Anonymous — Mon, 23 Nov 2020 17:37:48 +0000

Transformative Science from the Lunar Farside: Observations of the Dark Ages and Exoplanetary Systems at Low Radio Frequencies Anonymous (not verified) Mon, 11/23/2020 - 10:37

Author: Jack O. Burns

Abstract: The farside of the Moon is a pristine, quiet platform to conduct low radio frequency observations of the early Universe's Dark Ages, as well as space weather and magnetospheres associated with habitable exoplanets. In this paper, NASA-funded concept studies will be described including a lunar-orbiting spacecraft, DAPPER, that will measure the 21 cm global spectrum at redshifts 40-80, and an array of low frequency dipoles on the lunar farside surface, FARSIDE. DAPPER observations (17-38 MHz), using a single cross-dipole antenna, will measure the amplitude of the 21 cm spectrum to the level required to distinguish the standard {\Lambda}CDM cosmological model from those of additional cooling models possibly produced by exotic physics such as dark matter interactions. FARSIDE has a notional architecture consisting of 128 dipole antennas deployed across a 10 km area by a rover. FARSIDE would image the entire sky each minute in 1400 channels over 0.1-40 MHz. This would enable monitoring of the nearest stellar systems for the radio signatures of coronal mass ejections and energetic particle events, and would also detect the magnetospheres of the nearest candidate habitable exoplanets. In addition, FARSIDE would determine the Dark Ages global 21 cm signal at yet lower frequencies and provide a pathfinder for power spectrum measurements. Read more via the Philosophical Transactions of the Royal Society A online research articles.

Jack O. Burns

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Quasi-equilibrium models of high-redshift disc galaxy evolution

Anonymous — Tue, 03 Nov 2020 17:02:01 +0000

Quasi-equilibrium models of high-redshift disc galaxy evolution Anonymous (not verified) Tue, 11/03/2020 - 10:02

Author: Steven R. Furlanetto

Abstract: In recent years, simple models of galaxy formation have been shown to provide reasonably good matches to available data on high-redshift luminosity functions. However, these prescriptions are primarily phenomenological, with only crude connections to the physics of galaxy evolution. Here we introduce a set of galaxy models that are based on a simple physical framework but incorporate more sophisticated models of feedback, star formation, and other processes. We apply these models to the high-redshift regime, showing that most of the generic predictions of the simplest models remain valid. In particular, the stellar mass--halo mass relation depends almost entirely on the physics of feedback (and is thus independent of the details of small-scale star formation) and the specific star formation rate is a simple multiple of the cosmological accretion rate. We also show that, in contrast, the galaxy's gas mass is sensitive to the physics of star formation, although the inclusion of feedback-driven star formation laws significantly changes the naive expectations. While these models are far from detailed enough to describe every aspect of galaxy formation, they inform our understanding of galaxy formation by illustrating several generic aspects of that process, and they provide a physically-grounded basis for extrapolating predictions to faint galaxies and high redshifts currently out of reach of observations. If observations show violations from these simple trends, they would indicate new physics occurring inside the earliest generations of galaxies. Read more via the arVix.

Steven R. Furlanetto

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Ensuring Robustness in Training Set Based Global 21-cm Cosmology Analysis

Anonymous — Mon, 02 Nov 2020 23:18:26 +0000

Ensuring Robustness in Training Set Based Global 21-cm Cosmology Analysis Anonymous (not verified) Mon, 11/02/2020 - 16:18

Authors: Neil Bassett, David Rapetti, Keith Tauscher, Jack Burns, Joshua Hibbard

Abstract: We present a methodology for ensuring the robustness of our analysis pipeline in separating the global 21-cm hydrogen cosmology signal from large systematics based on singular value decomposition (SVD) of training sets. We show how traditional goodness-of-fit metrics such as the χ2 statistic that assess the fit to the full data may not be able to detect a suboptimal extraction of the 21-cm signal when it is fit alongside one or more additional components due to significant covariance between them. However, we find that comparing the number of SVD eigenmodes for each component chosen by the pipeline for a given fit to the distribution of eigenmodes chosen for synthetic data realizations created from training set curves can detect when one or more of the training sets is insufficient to optimally extract the signal. Furthermore, this test can distinguish which training set (e.g. foreground, 21-cm signal) needs to be modified in order to better describe the data and improve the quality of the 21-cm signal extraction. We also extend this goodness-of-fit testing to cases where a prior distribution derived from the training sets is applied and find that, in this case, the χ2 statistic as well as the recently introduced ψ2 statistic are able to detect inadequacies in the training sets due to the increased restrictions imposed by the prior. Crucially, the tests described in this paper can be performed when analyzing any type of observations with our pipeline. Read more via the arVix.

Neil Bassett, David Rapetti, Keith Tauscher, Jack Burns, Joshua Hibbard

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