The physical origins of low-mass spin bias

• Published in: Monthly notices of the Royal Astronomical Society Vol. 500; no. 3; pp. 2777 - 2785
• Main Authors: Tucci, Beatriz, Montero-Dorta, Antonio D, Abramo, L Raul, Sato-Polito, Gabriela, Artale, M Celeste
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01-01-2021
• Subjects: methods: statistical; methods: numerical; dark matter; large-scale structure of Universe; galaxies: haloes; cosmology: theory
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/staa3319

ABSTRACT
At z = 0, higher-spin haloes with masses above $\log (M_{\text{c}}/h^{-1}\, \text{M}_\odot)\simeq 11.5$ have a higher bias than lower-spin haloes of the same mass. However, this trend is known to invert below this characteristic crossover mass, Mc. In this paper, we measure the redshift evolution and scale dependence of halo spin bias at the low-mass end and demonstrate that the inversion of the signal is entirely produced by the effect of splashback haloes. These low-mass haloes tend to live in the vicinity of significantly more massive haloes, thus sharing their large-scale bias properties. We further show that the location of the redshift-dependent crossover mass scale Mc(z) is completely determined by the relative abundance of splashbacks in the low- and high-spin subpopulations. Once splashback haloes are removed from the sample, the intrinsic mass dependence of spin bias is recovered. Since splashbacks have been shown to account for some of the assembly bias signal at the low-mass end, our results unveil a specific link between two different secondary bias trends: spin bias and assembly bias.