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

TL;DR

This paper introduces an enhanced global sky model for diffuse galactic radio emission covering 10 MHz to 5 THz, utilizing advanced algorithms and new data to improve component separation and accuracy for cosmological studies.

Contribution

The authors develop a generalized PCA method for non-overlapping sky maps and perform a blind separation that identifies physical emission components without prior assumptions.

Findings

Successfully separates five physical components of galactic emission.

Achieves smaller error bars compared to previous models.

Provides an accessible online version of the improved GSM.

Abstract

We present an improved Global Sky Model (GSM) of diffuse galactic radio emission from 10 MHz to 5 THz, whose uses include foreground modeling for 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, with maps and spectra agreeing with previous work but in many cases with smaller error bars. The improved GSM is available online at github.com/jeffzhen/gsm2016.