Evidence for inverse Compton scattering in high-redshift Lyman-break galaxies

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dc.contributor.authorWhittam, Imogen H.
dc.contributor.authorJarvis, Matthew J.
dc.contributor.authorTaylor, Andrew Russell
dc.contributor.authorVaccari, Mattia
dc.date.accessioned2026-01-20T09:18:38Z
dc.date.available2026-01-20T09:18:38Z
dc.date.issued2025
dc.description.abstractRadio continuum emission provides a unique opportunity to study star formation unbiased by dust obscuration. However, if radio observations are to be used to accurately trace star formation to high redshifts, it is crucial that the physical processes that affect the radio emission from star-forming galaxies are well understood. While inverse Compton (IC) losses from the cosmic microwave background (CMB) are negligible in the local universe, the rapid increase in the strength of the CMB energy density with redshift [∼ (1 + z)4] means that this effect becomes increasingly important at z ≿ 3. Using a sample of ∼ 200 000 high-redshift (3 < z < 5) Lyman-break galaxies selected in the rest-frame ultraviolet (UV), we have stacked radio observations from the MIGHTEE survey to estimate their 1.4-GHz flux densities. We find that for a given rest-frame UV magnitude, the 1.4-GHz flux density and luminosity decrease with redshift. We compare these results to the theoretical predicted effect of energy losses due to IC scattering off the CMB, and find that the observed decrease is consistent with this explanation. We discuss other possible causes for the observed decrease in radio flux density with redshift at a given UV magnitude, such as a top-heavy initial mass function at high redshift or an evolution of the dust properties, but suggest that IC scattering is the most compelling explanation.
dc.identifier.citationWhittam, I.H., Jarvis, M.J., Murphy, E.J., Adams, N.J., Bowler, R.A.A., Matthews, A., Varadaraj, R.G., Hale, C.L., Heywood, I., Knowles, K. and Marchetti, L., 2025. Evidence for inverse Compton scattering in high-redshift Lyman-break galaxies. Monthly Notices of the Royal Astronomical Society, 543(1), pp.507-517.
dc.identifier.urihttps://doi.org/10.1093/mnras/staf1505
dc.identifier.urihttps://hdl.handle.net/10566/21759
dc.language.isoen
dc.publisherOxford University Press
dc.subjectGalaxies: evolution
dc.subjectGalaxies: high-redshift
dc.subjectGalaxies: statistics
dc.subjectRadio continuum: Galaxies
dc.subjectScattering
dc.titleEvidence for inverse Compton scattering in high-redshift Lyman-break galaxies
dc.typeArticle

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