An Improved Model of Diffuse Galactic Radio Emission from 10 MHz to 5 THz

Abstract

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society We present an improved Global Sky Model (GSM) of diffuse Galactic radio emission from 10 MHz to 5 THz, whose uses include foreground modelling for cosmic microwave background (CMB) and 21 cm cosmology. Our model improves on past work both algorithmically and by adding new data sets such as the Planck maps and the enhanced Haslam map. Our method generalizes the principal component analysis approach to handle non-overlapping regions, enabling the inclusion of 29 sky maps with no region of the sky common to all. We also perform a blind separation of our GSM into physical components with a method that makes no assumptions about physical emission mechanisms (synchrotron, free-free, dust, etc). Remarkably, this blind method automatically finds five components that have previously only been found 'by hand', which we identify with synchrotron, free-free, cold dust, warm dust, and the CMB anisotropy. Computing the cross-power spectrum between these blindly extracted components and Planck component maps, we find a strong correlation at all angular scales. The improved GSM is available online at http://github.com/jeffzhen/gsm2016.