A model of diffuse Galactic radio emission from 10 MHz to 100 GHz

Abstract

Understanding diffuse Galactic radio emission is interesting both in its own right and for minimizing foreground contamination of cosmological measurements. cosmic microwave background experiments have focused on frequencies 10 GHz, whereas 21-cm tomography of the high-redshift universe will mainly focus on 0.2 GHz, for which less is currently known about Galactic emission. Motivated by this, we present a global sky model derived from all publicly available total power large-area radio surveys, digitized with optical character recognition when necessary and compiled into a uniform format, as well as the new Villa Elisa data extending the 1.42-GHz map to the entire sky. We quantify statistical and systematic uncertainties in these surveys by comparing them with various global multifrequency model fits. We find that a principal component based model with only three components can fit the 11 most accurate data sets (at 10, 22, 45 and 408 MHz and 1.42, 2.326, 23, 33, 41, 61, 94 GHz) to an accuracy around 1-10 per cent depending on frequency and sky region. Both our data compilation and our software returning a predicted all-sky map at any frequency from 10 MHz to 100 GHz are publicly available at http://space.mit.edu/home/angelica/gsm.

Improved measurement of the spectral index of the diffuse radio background between 90 and 190 MHz

“…8 that beam correction has a significant impact on the recovered spectral index. Without correction, the beam effects mask the flattening that is expected near the Galactic Centre (de Oliveira-Costa et al 2008;Guzmán et al 2011).…”

“…These results improve on the earlier findings of by reducing the spectral index uncertainty from 0.10 to 0.02 while considering more extensive sources of errors. We compare our measurements with spectral index simulations derived from the Global Sky Model (GSM) of de Oliveira-Costa et al (2008) and with fits between the Guzmán et al (2011) 45 MHz andHaslam et al (1982) 408 MHz maps. We find good agreement at the transit of the Galactic Centre.…”

“…Improvements to the map have occurred throughout the years, including efforts by Davies et al (1996); Bennett et al (2003a,b); Platania et al (2003), and Remazeilles et al (2015) that focused on removing point sources and destriping the original data. de Oliveira-Costa et al (2008) combined the Haslam 408 MHz map and several other surveys between 10 MHz and 94 GHz to build a Global Sky Model (GSM), which provides spectral properties of the diffuse emission of the entire sky. In this model at 150 MHz, the spectral index outside the Galactic plane is ∼ −2.6 and in the Galactic plane (in a narrow band) increases to ∼ −2.5 with peaks as high as ∼ −2.3.…”

Studying Galactic interstellar turbulence through fluctuations in synchrotron emission

“…The frequency dependence of the spectral index for the synchrotron brightness temperature has been investigated by several authors, e.g. de Oliveira-Costa et al (2008) and recently Kogut (2012). For a spectral index of β = −2.64 ± 0.03 (Kogut 2012), the corresponding sky temperature at 150 MHz is T I 150 = 632 ± 32 K. Next the isotropic extragalactic background component is subtracted.…”

Optical–infrared flares and radio afterglows by Jovian planets inspiraling into their host stars

“…(26) Table 2 shows the results for different values of p with fixed parameters, nc = η−5 = B−5 = γm = 1. For comparison, the surface brightness of the faintest Galactic supernova remnants is ∼ 10 4 Jy sr −1 (Arbutina & Urošević 2005), of the same order as the typical value of the diffuse Galactic radio emission (e.g., de Oliveira-Costa et al 2008).…”