EMU: Cross-correlating EMU Pilot Survey 1 with Dark Energy Survey to validate the radio galaxy bias and redshift distribution

Chandra Shekhar Saraf; David Parkinson; Jacobo Asorey; Catherine L. Hale; Benedict Bahr-Kalus; Maciej Bilicki; Stefano Camera; Andrew M. Hopkins; Konstantinos Tanidis

arXiv · 2505.05821

EMU: Cross-correlating EMU Pilot Survey 1 with Dark Energy Survey to validate the radio galaxy bias and redshift distribution

Chandra Shekhar Saraf·David Parkinson·Jacobo Asorey·Catherine L. Hale·Benedict Bahr-Kalus·Maciej Bilicki·Stefano Camera·Andrew M. Hopkins·Konstantinos Tanidis

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Abstract

Radio continuum galaxy surveys can provide a relatively fast map of the projected distribution of structure in the Universe, at the cost of lacking information about the radial distribution. We can use these surveys to learn about the growth of structure and the fundamental physics of the Universe, but doing so requires extra information to be provided in the modelling of the redshift distribution, $dN/dz$. In this work, we show how the cross-correlation of the two-dimensional radio continuum map with another galaxy map (in this case a photometric optical extragalactic survey), with a known redshift distribution, can be used to determine the redshift distribution through statistical inference. We use data from the Evolutionary Map of the Universe (EMU) Pilot Survey 1 and cross-correlate it with optical data from the Dark Energy Survey to fit the parameters of our $dN/dz$ model. We show that the recovered distribution has a similar shape to the distribution predicted by the current state-of-the-art simulation, and can fit the angular power spectrum data from cross-correlations very well, validating this model. These results will have significance for future cosmological analyses with large-scale radio continuum surveys such as the full EMU, or with the SKAO.

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Chandra Shekhar Saraf, David Parkinson, Jacobo Asorey, Catherine L. Hale, Benedict Bahr-Kalus, Maciej Bilicki, Stefano Camera, Andrew M. Hopkins, Konstantinos Tanidis. 2026-06-25. EMU: Cross-correlating EMU Pilot Survey 1 with Dark Energy Survey to validate the radio galaxy bias and redshift distribution. https://arxiv.org/abs/2505.05821

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