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  3. 1 CONTRIBUTI IN RIVISTE (Journal articles)
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Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/32314
Title: Spectral index of the Galactic foreground emission in the 50-87 MHz range
Authors: SPINELLI, MARTA 
BERNARDI, GIANNI 
Garsden, H.
Greenhill, L. J.
Fialkov, A.
Dowell, J.
Price, D. C.
Issue Date: 2021
Journal: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 
Number: 505
Issue: 2
First Page: 1575
Abstract: Total-power radiometry with individual meter-wave antennas is a potentially effective way to study the Cosmic Dawn (z ~ 20) through measurement of the 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 analyse a subset of data from the Large-aperture Experiment to Detect the Dark Age (LEDA) in the 50-87 MHz range and constrain the foreground spectral index β in the northern sky visible from mid-latitudes. We focus on two zenith-directed LEDA radiometers and study how estimates of β vary with local sidereal time (LST). We correct for the effect of gain pattern chromaticity and compare estimated absolute temperatures with simulations. We select a reference data set consisting of 14 d of observations in optimal conditions. Using this data set, we find, for one radiometer, that β varies from -2.55 at LST <6 h to a steeper -2.58 at LST ~13 h, consistently with sky models and previous southern sky measurements. In the 13 - 24 h LST range, however, we find that β varies between -2.55 and -2.61 (data scatter ~0.01). We observe a similar β versus LST trend for the second radiometer, although with slightly smaller |β| over the 24 h, in the -2.46 < β < -2.43 range (data scatter ~ 0.02). Combining all data gathered during the extended campaign between mid-2018 and mid-2019, and focusing on the LST = 9-12.5 h range, we infer good instrument stability and find -2.56 < β < -2.50 with 0.09 < Δβ < 0.12.
URI: http://hdl.handle.net/20.500.12386/32314
URL: https://academic.oup.com/mnras/article/505/2/1575/6276736?login=true
http://arxiv.org/abs/2011.03994v2
ISSN: 0035-8711
DOI: 10.1093/mnras/stab1363
Bibcode ADS: 2021MNRAS.505.1575S
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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