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Pujol, Arnau and Skibba, Ramin A. and Gaztañaga, Enrique and Benson, Andrew and Blaizot, Jeremy and Bower, Richard and Carretero, Jorge and Castander, Francisco J. and Cattaneo, Andrea and Cora, Sofia A. and Croton, Darren J. and Cui, Weiguang and Cunnama, Daniel and De Lucia, Gabriella and Devriendt, Julien E. and Elahi, Pascal J. and Font, Andreea and Fontanot, Fabio and Garcia-Bellido, Juan and Gargiulo, Ignacio D. and Gonzalez-Perez, Violeta and Helly, John and Henriques, Bruno M. B. and Hirschmann, Michaela and Knebe, Alexander and Lee, Jaehyun and Mamon, Gary A. and Monaco, Pierluigi and Onions, Julian and Padilla, Nelson D. and Pearce, Frazer R. and Power, Chris and Somerville, Rachel S. and Srisawat, Chaichalit and Thomas, Peter A. and Tollet, Edouard and Vega-Martínez, Cristian A. and Yi, Sukyoung K. (2017) nIFTy cosmology: the clustering consistency of galaxy formation models. Monthly Notices of the Royal Astronomical Society, 469 (1). pp. 749-762. ISSN 1365-2966

Abstract

We present a clustering comparison of 12 galaxy formation models [including semi-analytic models (SAMs) and halo occupation distribution (HOD) models] all run on halo catalogues and merger trees extracted from a single _ cold dark matter N-body simulation. We compare the results of the measurements of the mean halo occupation numbers, the radial distribution of galaxies in haloes and the two-point correlation functions (2PCF). We also study the implications of the different treatments of orphan (galaxies not assigned to any dark matter subhalo) and non-orphan galaxies in these measurements. Our main result is that the galaxy formation models generally agree in their clustering predictions but they disagree significantly between HOD and SAMs for the orphan satellites. Although there is a very good agreement between the models on the 2PCF of central galaxies, the scatter between the models when orphan satellites are included can be larger than a factor of 2 for scales smaller than 1 h−1 Mpc. We also show that galaxy formation models that do not include orphan satellite galaxies have a significantly lower 2PCF on small scales, consistent with previous studies. Finally, we show that the 2PCF of orphan satellites is remarkably different between SAMs and HOD models. Orphan satellites in SAMs present a higher clustering than in HOD models because they tend to occupy more massive haloes. We conclude that orphan satellites have an important role on galaxy clustering and they are the main cause of the differences in the clustering between HOD models and SAMs.

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