Galaxy bias of radio AGN and star-forming galaxies from MIGHTEE and CMB lensing
Abstract
Radio galaxies play a significant role in galaxy evolution through feedback mechanisms, making it important to characterize the environments in which they reside. We measure the cross-correlation between the positions of radio sources in the MIGHTEE survey and cosmic microwave background lensing measurements from the Atacama Cosmology Telescope over 20 deg2 to flux densities S1.4 GHz>40 μJy, detecting the signal at ∼4σ significance. By combining this with auto-correlation measurements of low- and high-redshift radio samples, we constrain the redshift evolution of the galaxy bias parameter, b(z). Fitting different models for the redshift evolution of the bias, we find that both a model inversely proportional to the linear growth factor, b(z) = (1.63+0.19−0.22)/D(z), and a model where bias grows linearly with redshift, b(z) = (0.49+0.44−0.32) + (1.62+0.37−0.51)z, provide comparably good fits to the data, with the current measurements unable to distinguish between them. Using a radio luminosity function, we estimate the fraction of sources that are active galactic nuclei (AGNs) or star-forming galaxies (SFGs) as a function of redshift, and model the individual contributions of AGNs and SFGs to the total bias. This approach allows us to measure the bias of AGNs and SFGs without individual source classifications. Though no single model is favoured significantly, the best-fitting model gives bAGN(z) = (2.60+0.65−0.91)/D(z) compared to bSFG(z) = (0.52+0.47−0.34)/D(z). Incorporating SFG bias measurements from previous work as a prior tightens these constraints to bAGN(z) = (1.96+0.37−0.40)/D(z) and bSFG(z) = (0.90+0.06−0.06)/D(z).
Related
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- Mapping large-scale structure without galaxy formation - combining fast radio bursts with CMB lensing
- The quest for high-redshift radio galaxies II. Discovery of the most powerful known radio galaxy at z=4.946
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BibTeX
@misc{hamlett2026galaxy,
title = {{Galaxy bias of radio AGN and star-forming galaxies from MIGHTEE and CMB lensing}},
author = {Joel Hamlett and Catherine L. Hale and Matt J. Jarvis and David Alonso and S. Lyla Jung and Natalia Stylianou and Rohan G. Varadaraj},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.23567},
eprint = {2610.23567},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.23567},
}
RIS
TY - UNPB
TI - Galaxy bias of radio AGN and star-forming galaxies from MIGHTEE and CMB lensing
AU - Joel Hamlett
AU - Catherine L. Hale
AU - Matt J. Jarvis
AU - David Alonso
AU - S. Lyla Jung
AU - Natalia Stylianou
AU - Rohan G. Varadaraj
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.23567
UR - https://arxiv.org/abs/2610.23567
AB - Radio galaxies play a significant role in galaxy evolution through feedback mechanisms, making it important to characterize the environments in which they reside. We measure the cross-correlation between the positions of radio sources in the MIGHTEE survey and cosmic microwave background lensing measurements from the Atacama Cosmology Telescope over 20 deg^2 to flux densities S_1.4 GHz>40 μJy, detecting the signal at ∼4σ significance. By combining this with auto-correlation measurements of low- and high-redshift radio samples, we constrain the redshift evolution of the galaxy bias parameter, b(z). Fitting different models for the redshift evolution of the bias, we find that both a model inversely proportional to the linear growth factor, b(z) = (1.63^+0.19_−0.22)/D(z), and a model where bias grows linearly with redshift, b(z) = (0.49^+0.44_−0.32) + (1.62^+0.37_−0.51)z, provide comparably good fits to the data, with the current measurements unable to distinguish between them. Using a radio luminosity function, we estimate the fraction of sources that are active galactic nuclei (AGNs) or star-forming galaxies (SFGs) as a function of redshift, and model the individual contributions of AGNs and SFGs to the total bias. This approach allows us to measure the bias of AGNs and SFGs without individual source classifications. Though no single model is favoured significantly, the best-fitting model gives b_AGN(z) = (2.60^+0.65_−0.91)/D(z) compared to b_SFG(z) = (0.52^+0.47_−0.34)/D(z). Incorporating SFG bias measurements from previous work as a prior tightens these constraints to b_AGN(z) = (1.96^+0.37_−0.40)/D(z) and b_SFG(z) = (0.90^+0.06_−0.06)/D(z).
ER -