# The environments of radio galaxies and quasars in LoTSS data release 2

**Authors:** Tong Pan, Yuming Fu, H. J. A. Rottgering, R. J. van Weeren, A. B. Drake, B. H. Yue, J. W. Petley  
**arXiv:** [2503.01055](https://arxiv.org/abs/2503.01055)  
**Date:** 2025-03-02  
**Summary page:** https://www.summarizepaper.com/en/paper/2503.01055v1/

## Key points

- Study examines orientation-based unification scheme for radio-loud AGNs
- Data from LoTSS DR2 used to compare environments of 26,577 radio galaxies and 2028 quasars (z range: 0.08 < z < 0.4)
- Radio galaxies classified into LERGs and HERGs based on optical spectra
- Approximately $17.1 \pm 0.2%$ of radio galaxies and $4.1 \pm 0.4%$ of quasars associated with galaxy clusters
- Luminous quasars less common in clusters compared to LERGs and HERGs
- HERGs and LERGs tend to reside in central regions of galaxy clusters, while quasars show no strong preference
- Findings challenge orientation-based unification model, suggesting other factors beyond viewing angle play significant role
- Future surveys like WEAVE-LOFAR expected to provide more comprehensive data for larger sample, allowing deeper exploration of AGN environments

## Summary

The study "The Environments of Radio Galaxies and Quasars in LoTSS Data Release 2" by Tong Pan, Yuming Fu, H. J. A. Rottgering, R. J. van Weeren, A. B. Drake, B. H. Yue, and J.W Petley examines the orientation-based unification scheme for radio-loud active galactic nuclei (AGNs). The authors use data from the LOFAR Two-metre Sky Survey (LoTSS DR2) to compare the environments of 26,577 radio galaxies and 2028 quasars within a redshift range of 0.08 < z < 0.4. They also classify radio galaxies into low-excitation (LERGs) and high-excitation (HERGs) categories based on their optical spectra. By crossmatching these samples with galaxy cluster catalogs from the Sloan Digital Sky Survey (SDSS), the researchers find that approximately $17.1 \pm 0.2%$ of radio galaxies and $4.1 \pm 0.4%$ of quasars are associated with galaxy clusters. Interestingly, luminous quasars are less common in clusters compared to LERGs and HERGs. Furthermore, the study reveals that both HERGs and LERGs tend to reside in the central regions of galaxy clusters while quasars do not show a strong preference for any particular location within these structures. These findings challenge the orientation-based unification model by suggesting that factors beyond just viewing angle may play a significant role in differentiating between radio galaxies and quasars based on their environmental characteristics. Looking ahead, future surveys like WEAVE-LOFAR are expected to provide more comprehensive data for a larger sample of radio sources, allowing for a deeper exploration of the environments surrounding these objects. This study provides valuable insights into the distinct properties and distributions of different types of AGNs in varying cosmic environments, shedding light on the complexities underlying their classification and evolution processes in the universe.