Measuring the diffuse Galactic synchrotron spectral index and curvature between 45 and 2300 MHz

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• Dr. Melis Irfan (Institute of Astronomy, University of Cambridge)
• Tuesday 20 January 2026, 11:15-12:00
• Coffee area, Battcock Centre.

If you have a question about this talk, please contact Charles Walker.

Cosmic Microwave Background and 21cm experiments aim to probe the inflationary period and map the reionization history of the Universe from the Big Bang through to Cosmic Dawn and the formation of Large-Scale Structure. These two complementary fields span the radio to microwave frequency regimes and share a common, pernicious foreground contamination: diffuse Galactic synchrotron emission. Synchrotron emission is the dominant diffuse Galactic emission in intensity across the majority of the sky at frequencies under 1 GHz and at microwave frequencies it makes up one of the two polarised CMB contaminants.

Although believed to follow a power law distribution in terms of change in temperature across frequency, diffuse Galactic synchrotron emission is particularly difficult to simulate realistically due to its spatially and spectrally varying spectral index. We present all-sky maps of the diffuse Galactic synchrotron spectral index and spectral index curvature between 45 and 2300 MHz at 1 degree resolution constructed from 36 publicly available, partial sky surveys each with differing resolutions. The spectral index and curvature maps, alongside the Haslam 408 MHz data, can be used to construct a synchrotron emission model which we show to be more accurate than the Global Sky Model and Python Sky Model within the 45 and 2300 MHz frequency range.

This talk is part of the Hills Coffee Talks series.

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