GMOSS: All-sky model of spectral radio brightness based on physical components and associated radiative processes

Abstract

We present Global MOdel for the radio Sky Spectrum (GMOSS) -- a novel, physically motivated model of the low-frequency radio sky from 22 MHz to 23 GHz. GMOSS invokes different physical components and associated radiative processes to describe the sky spectrum over 3072 pixels of $5^{\circ }$ resolution. The spectra are allowed to be convex, concave or of more complex form with contributions from synchrotron emission, thermal emission and free-free absorption included. Physical parameters that describe the model are optimized to best fit four all-sky maps at 150 MHz, 408 MHz, 1420 MHz and 23 GHz and two maps at 22 MHz and 45 MHz generated using the Global Sky Model of de Oliveira-Costa et al. (2008). The fractional deviation of model to data has a median value of $6\%$ and is less than $17\%$ for $99\%$ of the pixels. Though aimed at modeling of foregrounds for the global signal arising from the redshifted 21-cm line of Hydrogen during Cosmic Dawn and Epoch of Reionization (EoR) - over redshifts $150\lesssim z\lesssim 6$, GMOSS is well suited for any application that requires simulating spectra of the low-frequency radio sky as would be observed by the beam of any instrument. The complexity in spectral structure that naturally arises from the underlying physics of the model provides a useful expectation for departures from smoothness in EoR foreground spectra and hence may guide the development of algorithms for EoR signal detection. This aspect is further explored in a subsequent paper.

19 pages, 7 figures

References in corpus (8)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• Spectral Index of the Diffuse Radio Background Measured From 100 to 200 MHz
• Toward Empirical Constraints on the Global Redshifted 21 cm Brightness Temperature During the Epoch of Reionization
• Simulating polarized Galactic synchrotron emission at all frequencies, the Hammurabi code
• Foreground Model and Antenna Calibration Errors in the Measurement of the Sky-Averaged λ21 cm Signal at z~20
• SARAS measurement of the Radio Background at long wavelengths
• Erasing the variable: Empirical foreground discovery for global 21 cm spectrum experiments
• Selection between foreground models for global 21-cm experiments

Cited by in corpus (20)

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• Spectral Index of the Diffuse Radio Background Between 50 and 100 MHz
• A Space-Based Observational Strategy for Characterizing the First Stars and Galaxies Using the Redshifted 21-cm Global Spectrum
• SARAS 3 CD/EoR Radiometer: Design and Performance of the Receiver
• Antenna beam characterisation for the global 21cm experiment LEDA and its impact on signal model parameter reconstruction
• An Ultra-long Wavelength Sky Model with Absorption Effect
• PRATUSH experiment concept and design overview
• Absolute Calibration of Diffuse Radio Surveys at 45 and 150 MHz
• The All-Sky SignAl Short-Spacing INterferometer (ASSASSIN) I: Global sky measurements with the Engineering Development Array-2
• Sky-averaged 21-cm signal extraction using multiple antennas with an SVD framework: the REACH case
• RHINO: A large horn antenna for detecting the 21cm global signal
• Sensitivity of Bayesian 21 cm power spectrum estimation to foreground model errors
• Direction-dependent effects on global 21-cm detection
• STARFIRE: An algorithm for estimating radio frequency interference in orbits around Earth
• Uncertainties of the 30-408 MHz Galactic emission as a calibration source for radio detectors in astroparticle physics
• Synthetic Observations with the Square Kilometre Array (SKA) -- development towards an end-to-end pipeline
• Bayesian recalibration of flux scale factors in diffuse radio maps using low-resolution absolute radiometers
• A Comprehensive Bayesian re-analysis of the SARAS2 data from the Epoch of Reionization
• A Multi-Site Study of Radio Environment for Cosmology Experiments
• System design and calibration of SITARA -- a global 21 cm short spacing interferometer prototype