Description
The Haslam 408 MHz all-sky map is widely used as a template to model the Galactic synchrotron emission across the radio and microwave regions of the electromagnetic spectrum. However, recent studies have suggested that there may be uncorrected gain factors -- in addition to systematic effects, spatial variations, and curvature -- in the map. We address the former by applying a Bayesian statistical method combining Gibbs sampling and Gaussian-constrained realisation techniques to constrain the gain factors and the true sky signal of our mock sky map using data from low-frequency radio experiments. We test our method on two sets of mock data with gain variations corresponding to: 1) different zones in the sky, and 2) certain $\ell_{max}$ in spherical harmonic space. This method will permit low-resolution absolutely-calibrated data, e.g. from 21cm global signal experiments, to be used to "fix" the Haslam map in a robust manner.
