Galaxy bias of radio AGN and star-forming galaxies from MIGHTEE and CMB lensing
- 1Astrophysics, University of Oxford, Denys Wilkinson Building , Keble Road, Oxford, OX1 3RH ,
- 2School of Physics and Astronomy, Institute for Astronomy, University of Edinburgh , Royal Observatory, Blackford Hill, EH9 3HJ Edinburgh ,
- 3University of the Western Cape Department of Physics and Astronomy, , Robert Sobukwe Road, 7535 Bellville, Cape Town ,
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 with 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).
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BibTeX
@article{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},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = oct,
doi = {10.1093/mnras/stag1983},
url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1983/8943786},
note = {CC BY 4.0},
}
RIS
TY - JOUR
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 - 2026/10/19
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1983
UR - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1983/8943786
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 with 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 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).
SN - 0035-8711
SN - 1365-2966
ER -