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We thank the anonymous referee for insightful comments that helped improve the presentation of this paper. This work was made possible by the efforts of Gerard Lemson and colleagues at the German Astronomical Virtual Observatory in setting up the Millennium Simulation data base in Garching. EJ, SC, NP, and IZ acknowledge the hospitality of the ICC at Durham University. EJ acknowledges support from 'Centro de Astronomia y Tecnologias Afines' BASAL 170002. SC acknowledges the support of the 'Juan de la Cierva formacion' fellowship (FJCI-2017-33816). NP acknowledges support from Fondecyt Regular 1191813. IZ acknowledges support by NSF grant AST-1612085. This project has received funding from the European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement no. 734374. The calculations for this paper were performed on the Geryon computer at the Center for AstroEngineering UC, part of the BASAL PFB-06, which received additional funding from QUIMAL 130008 and Fondequip AIC-57 for upgrades.

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Extensions to the halo occupation distribution model for more accurate clustering predictions

Publicated to:MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. 490 (3): 3532-3544 - 2019-01-01 490(3), DOI: 10.1093/mnras/stz2790

Authors: Jimenez, Esteban; Contreras, Sergio; Padilla, Nelson; Zehavi, Idit; Baugh, Carlton M.; Gonzalez-Perez, Violeta;

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Abstract

We test different implementations of the halo occupation distribution (HOD) model to reconstruct the spatial distribution of galaxies as predicted by a version of the L-GALAXIES semi-analytical model (SAM). We compare the measured two-point correlation functions of the HOD mock catalogues and the SAM samples to quantify the fidelity of the reconstruction. We use fixed number density galaxy samples selected according to stellar mass or star formation rate (SFR). We develop three different schemes to populate haloes with galaxies with increasing complexity, considering the scatter of the satellite HOD as an additional parameter in the modelling. We modify the SAM output, removing assembly bias and using a standard Navarro-Frenk-White density profile for the satellite galaxies as the target to reproduce with our HOD mocks. We find that all models give similar reproductions of the two-halo contribution to the clustering signal, but there are differences in the one-halo term. In particular, the HOD mock reproductions work equally well using either the HOD of central and satellites separately or using a model that also accounts for whether or not the haloes contain a central galaxy. We find that the HOD scatter does not have an important impact on the clustering predictions for stellar mass-selected samples. For SFR selections, we obtain the most accurate results assuming a negative binomial distribution for the number of satellites in a halo. The scatter in the satellites HOD is a key consideration for HOD mock catalogues that mimic ELG or SFR-selected samples in future galaxy surveys.

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