Subhalo abundance matching and assembly bias in the EAGLE simulation

Chaves-Montero, J.; Angulo, R.E.; Schaye, J.; Schaller, M.; Crain, R.A.; Furlong, M.; Theuns, T.

Abstract

Subhalo abundance matching (SHAM) is a widely used method to connect galaxies with dark matter structures in numerical simulations. SHAM predictions agree remarkably well with observations, yet they still lack strong theoretical support. We examine the performance, implementation, and assumptions of SHAM using the ‘Evolution and Assembly of Galaxies and their Environment’ (EAGLE) project simulations. We find that Vrelax, the highest value of the circular velocity attained by a subhalo while it satisfies a relaxation criterion, is the subhalo property that correlates most strongly with galaxy stellar mass (Mstar). Using this parameter in SHAM, we retrieve the real-space clustering of EAGLE to within our statistical uncertainties on scales greater than 2 Mpc for galaxies with 8.77 < log 10(Mstar[M⊙]) < 10.77. Conversely, clustering is overestimated by 30 per cent on scales below 2 Mpc for galaxies with 8.77 < log 10(Mstar[M⊙]) < 9.77 because SHAM slightly overpredicts the fraction of satellites in massive haloes compared to EAGLE. The agreement is even better in redshift space, where the clustering is recovered to within our statistical uncertainties for all masses and separations. Additionally, we analyse the dependence of galaxy clustering on properties other than halo mass, i.e. the assembly bias. We demonstrate assembly bias alters the clustering in EAGLE by 20  per cent and Vrelax captures its effect to within 15  per cent. We trace small differences in the clustering to the failure of SHAM as typically implemented, i.e. the Mstar assigned to a subhalo does not depend on (i) its host halo mass, (ii) whether it is a central or a satellite. In EAGLE, we find that these assumptions are not completely satisfied.

Citation

Chaves-Montero, J., Angulo, R., Schaye, J., Schaller, M., Crain, R., Furlong, M., & Theuns, T. (2016). Subhalo abundance matching and assembly bias in the EAGLE simulation. Monthly Notices of the Royal Astronomical Society, 460(3), 3100-3118. https://doi.org/10.1093/mnras/stw1225

• Journal Article Type: Article
• Acceptance Date: May 19, 2016
• Online Publication Date: May 23, 2016
• Publication Date: Aug 11, 2016
• Deposit Date: Aug 18, 2016
• Publicly Available Date: Aug 19, 2016
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 460
• Issue: 3
• Pages: 3100-3118
• DOI: https://doi.org/10.1093/mnras/stw1225
• Public URL: https://durham-repository.worktribe.com/output/1406129