Cosmology from LOFAR Two-metre Sky Survey Data Release 2: Cross-correlations with luminous red galaxies from eBOSS

¹ Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany
² Department of Physics, Guangdong Technion – Israel Institute of Technology, Shantou, Guangdong 515063, PR China
³ National Astronomy Observatories, Chinese Academy of Sciences, Beijing 100101, PR China
⁴ School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, PR China
⁵ Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, PR China
⁶ Institute of Cosmology and Gravitation, University of Portsmouth, Burnaby Road, Portsmouth PO1 3FX, United Kingdom
⁷ Dipartimento di Fisica, Università degli Studi di Torino, Via P. Giuria 1, 10125 Torino, Italy
⁸ INFN – Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Via P. Giuria 1, 10125 Torino, Italy
⁹ INAF – Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy
¹⁰ Institut für Theoretische Physik, Universiät Heidelberg, Philosophenweg 16, 69120 Heidelberg, Germany
¹¹ Sub-department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹² Division of Physics, Mathematics and Astronomy, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA

^⋆ Corresponding authors: Zjzheng@physik.uni-bielefeld.de; prabhakar.tiwari@gtiit.edu.cn; gbzhao@nao.cas.cn

Received: 22 August 2024
Accepted: 30 March 2025

Abstract

Aims. We cross-correlated galaxies from the LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) second data release (DR2) radio source with the extended Baryon Oscillation Spectroscopic Survey (eBOSS) luminous red galaxy (LRG) sample to extract the baryon acoustic oscillation (BAO) signal and constrain the linear clustering bias of radio sources in LoTSS DR2.

Methods. In the LoTSS DR2 catalogue, employing a flux density limit of 1.5 mJy at the central LoTSS frequency of 144 MHz and a signal-to-noise ratio (S/N) of 7.5, additionally considering eBOSS LRGs with redshifts between 0.6 and 1, we measured both the angular LoTSS-eBOSS cross-power spectrum and the angular eBOSS auto-power spectrum. These measurements were performed across various eBOSS redshift tomographic bins with a width of Δz = 0.06. By marginalising over the broadband shape of the angular power spectra, we searched for a BAO signal in cross-correlation with radio galaxies, and determine the linear clustering bias of LoTSS radio sources for a constant-bias and an evolving-bias model.

Results. Using the cross-correlation, we measured the isotropic BAO dilation parameter as α = 1.01 ± 0.11 at z_eff = 0.63. By combining four redshift slices at z_eff = 0.63, 0.69, 0.75, and 0.81, we determined a more constrained value of α = 0.968_−0.095^+0.060. For the entire redshift range of z_eff = 0.715, we measured b_C = 2.64 ± 0.20 for the constant-bias model, b(z0) = b_C, and then b_D = 1.80 ± 0.13 for the evolving-bias model, b(z) = b_D/D(z), with D(z) denoting the growth rate of linear structures. Additionally, we measured the clustering bias for individual redshift bins.

Conclusions. We detected the cross-correlation of LoTSS radio sources and eBOSS LRGs at a 9.2σ statistical significance for one single redshift bin and at a 14.7σ significance when the four redshift bins were combined. For the BAO signal, we achieved a significance of 2.2σ for a single redshift bin, 2.7σ for the combined cross-correlation and eBOSS auto-correlation, and 4σ for the combined analysis of four redshift bins in the cross-correlation, when assuming a Gaussian distribution for the BAO dilation parameter.