{
  "id": "1806.11417",
  "version": "v1",
  "published": "2018-06-29T13:55:48.000Z",
  "updated": "2018-06-29T13:55:48.000Z",
  "title": "Ghost busting: introducing a new, robust galaxy finder algorithm for simulations",
  "authors": [
    "Rodrigo Cañas",
    "Pascal J. Elahi",
    "Charlotte Welker",
    "Claudia del P. Lagos",
    "Chris Power",
    "Yohan Dubois",
    "Christophe Pichon"
  ],
  "comment": "Submitted to MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "Identifying galaxies in hydrodynamical simulations is a difficult task, particularly in regions of high density such as galaxy groups and clusters. We present a new scale-free shape-independent algorithm to robustly and accurately identify galaxies in simulation, implemented within the phase-space halo-finder code VELOCIraptor. This is achieved by using the full phase-space dispersion tensor for particle assignment and an iterative adjustment of search parameters, which help us overcome common structure finding problems. We apply our improved method to the Horizon-AGN simulation and compare galaxy stellar masses ($M_*$), star formation rates (SFR) and sizes with the elaborate configuration-space halo finder, HaloMaker. Galaxies living in halos with $> 1$ galaxy are the most affected by the shortcomings of real-space finders, with their mass, SFR, and sizes being $> 2$ times larger (smaller) in the case of host (satellite) galaxies. Thus, our ability to measure minor/major merger rates and disentangle environmental effects in simulations can be generally hindered if the identification of galaxies is not treated carefully. Though large systematic differences are obtained on a one-to-one basis, the overall Galaxy Stellar Mass Function, the Star Formation Rate Function and mass-size relations are not greatly affected. This is due to isolated galaxies being the most abundant population, dominating broad statistics.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2018-06-29T13:55:48.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "robust galaxy finder algorithm",
      "simulation",
      "common structure finding problems",
      "ghost busting",
      "overall galaxy stellar mass function"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}