Scatter in the star formation rate–halo mass relation: secondary bias and its impact on line-intensity mapping
Year: 2025
Type: article
Abstract: ABSTRACT We use the IllustrisTNG cosmological hydrodynamical simulations to study the impact of secondary bias – specifically, the correlation between star formation rate (SFR) and halo bias at fixed halo mass – on the line-intensity mapping (LIM) power spectrum. In lim, the galaxy contributions are flux-weighted, and therefore depend on the luminosity of emission line. We show that the (ensemble-averaged) large-scale two-halo term of the power spectrum depends only on the mean luminosity–halo mass relation if the scatter is uncorrelated with halo bias. However, when luminosity correlates with halo bias at fixed mass, this assumption breaks down. For many emission lines (e.g. H $\alpha$), luminosity is strongly correlated with sfr, making the sfr-weighted power spectrum important to study. In IllustrisTNG, secondary bias increases the two-halo term of the sfr-weighted power spectrum by 5 per cent at $z \sim 1.5$ compared to a model with random scatter. We also find that sfrs of central and satellite galaxies are correlated, enhancing the one-halo term – which depends on the distribution of sfr inside the halo – by 10 per cent relative to random pairings. To mitigate secondary bias in the two-halo term, we identify halo concentration (for haloes with mass $\log M_h \lesssim 12$) and satellite mass (for $\log M_h \gtrsim 12$) as effective secondary parameters. These results highlight the need to account for secondary bias when building mock catalogues and interpreting lim observations.
Authors: Rui Lan Jun, Tom Theuns, Kana Moriwaki, Sownak Bose
Institutions: The University of Tokyo, Durham University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
Funders: Department for Business, Energy and Industrial Strategy, UK Government, UK Research and Innovation, Japan Society for the Promotion of Science London, European Commission, Durham University, University of Tokyo, Science and Technology Facilities Council, Japan Society for the Promotion of Science
Awards: G1251748267, Durham DiRAC-2 petascale facility, G1468651527, DiRAC-2.5 - the pathway to DiRAC Phase 3, G2309215924, G2368581224, G2768788806, G2843074508, G3722612171, G3864028297, Formation Processes of Heavy Elements in the Early Universe Elucidated by Superconducting Nanoelectronics, Large-Scale Numerical Simulations, and Data Science, G4251892262, G4406864956, G4831232377, DiRAC-2.5 DC - Operations 2017-2020, Excellence in Galaxies - Twinning the IAC, G7676826204, G768801584, G7724874892, DiRAC: Memory Intensive 2.5y, 次世代広域観測に向けた銀河形成モデルの研究, Formation Processes of Heavy Elements in the Early Universe Elucidated by Superconducting Nanoelectronics, Large-Scale Numerical Simulations, and Data Science, DiRAC: Memory Intensive 2.5x
OpenAlex ID: W4414080050