Erratum: Spectral index of the Galactic foreground emission in the 50–87 MHz range
M. Spinelli,Gianni Bernardi,Gianni Bernardi,H. Garsden,Lincoln J. Greenhill,Anastasia Fialkov,Jayce Dowell,Danny C. Price,Danny C. Price +8 more
TLDR
In this paper, a subset of data from the Large-aperture Experiment to Detect the Dark Age (LEDA) in the range $50-87$~MHz and constrain the foreground spectral index in the northern sky visible from mid-latitudes.Abstract:
Total-power radiometry with individual meter-wave antennas is a potentially effective way to study the Cosmic Dawn ($z\sim20$) through measurement of sky brightness arising from the $21$~cm transition of neutral hydrogen, provided this can be disentangled from much stronger Galactic and extra-galactic foregrounds. In the process, measured spectra of integrated sky brightness temperature can be used to quantify the foreground emission properties. In this work, we analyze a subset of data from the Large-aperture Experiment to Detect the Dark Age (LEDA) in the range $50-87$~MHz and constrain the foreground spectral index $\beta$ in the northern sky visible from mid-latitudes. We focus on two zenith-directed LEDA radiometers and study how estimates of $\beta$ vary with local sidereal time (LST). We correct for the effect of gain pattern chromaticity and compare estimated absolute temperatures with simulations. We develop a reference dataset consisting of 14 days of optimal condition observations. Using this dataset we estimate, for one radiometer, that $\beta$ varies from $-2.55$ at LST~$<6$~h to a steeper $-2.58$ at LST~$\sim13$~h, consistently with sky models and previous southern sky measurements. In the LST~$=13-24$~h range, however, we find that $\beta$ fluctuates between $-2.55$ and $-2.61$ (data scatter $\sim0.01$). We observe a similar $\beta$ vs. LST trend for the second radiometer, although with slightly smaller $|\beta|$, in the $-2.46<\beta<-2.43$ range, over $24$~h of LST (data scatter $\sim0.02$). Combining all data gathered during the extended campaign between mid-2018 to mid-2019, and focusing on the LST~$=9-12.5$~h range, we infer good instrument stability and find $-2.56<\beta<-2.50$ with $0.09<\Delta\beta<0.12$.read more
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Journal ArticleDOI
The REACH radiometer for detecting the 21-cm hydrogen signal from redshift z ≈ 7.5–28
Eloy de Lera Acedo,Dirk I. L. de Villiers,Nima Razavi-Ghods,Will Handley,Anastasia Fialkov,Alessio Magro,D. A. Anstey,H.T.J. Bevins,Riccardo Chiello,J. Cumner,Alec Josaitis,I. L. V. Roque,Peter Sims,Kilian H. Scheutwinkel,Paul Alexander,Gianni Bernardi,Steven Carey,Jean Cavillot,W. Croukamp,John Ely,Thomas Gessey-Jones,Quentin Gueuning,R. Hills,Gauri V. Kulkarni,Roberto Maiolino,P. Daniel Meerburg,Shikhar Mittal,Jonathan K. Pritchard,Ewald Puchwein,A. Saxena,E Shen,Oleg Smirnov,M. Spinelli,Kristian Zarb-Adami +33 more
TL;DR: The Radio Experiment for the Analysis of Cosmic Hydrogen (REACH) is a sky-averaged 21 cm experiment aiming at improving the current observations by tackling the issues faced by current instruments related to residual systematic signals in the data as mentioned in this paper .
Journal ArticleDOI
A 21-cm power spectrum at 48 MHz, using the owens valley long wavelength array
H. Garsden,H. Garsden,Lincoln J. Greenhill,Gianni Bernardi,Gianni Bernardi,Anastasia Fialkov,Danny C. Price,Danny C. Price,Daniel A. Mitchell,Jayce Dowell,M. Spinelli,Frank K. Schinzel +11 more
TL;DR: In this paper, a 2D cylindrical spatial power spectrum for data at 43.1-53.5 MHz incoherently integrated for 4 hours was presented, and an analysis of the array sensitivity was performed.
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Journal ArticleDOI
Heating and Ionization of the Intergalactic Medium by an Early X-Ray Background
TL;DR: In this article, the impact of an X-ray background, such as high-energy photons from early quasars, on the temperature and ionization of the intergalactic medium prior to reionization, before the fully ionized bubbles associated with individual sources have overlapped.
Peer Review
Snowmass2021 Cosmic Frontier White Paper: 21cm Radiation as a Probe of Physics Across Cosmic Ages
TL;DR: The 21 cm line refers to a forbidden transition in neutral hydrogen associated with alignment of spins of the proton and electron and is a very low energy transition that is emitted whenever there is neutral hydrogen in the Universe as discussed by the authors .
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On the contamination of the global 21-cm signal from polarized foregrounds
TL;DR: In this article, the authors investigate the impact of galactic polarized foregrounds on the extraction of the global 21 cm signal through realistic sky and dipole simulations both in a low frequency band from $50$ to $100$~MHz, where a 21~cm absorption profile is expected, and in a higher frequency band ($100-200$ ~MHz), the presence of a polarized contaminant with complex frequency structure can bias the amplitude and the shape of the reconstructed signal parameters in both bands.
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TL;DR: The Global Model for the Radio Sky Spectrum (GMOSS) as mentioned in this paper is a physically motivated model of the low-frequency radio sky from 22 MHz to 23 GHz, which can be used for any application that requires simulating spectra of the radio sky.
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