4.7 Article

The Impact of Assembly Bias on the Galaxy Content of Dark Matter Halos

Journal

ASTROPHYSICAL JOURNAL
Volume 853, Issue 1, Pages -

Publisher

IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/aaa54a

Keywords

cosmology: theory; galaxies: evolution; galaxies: formation; galaxies: halos; galaxies: statistics

Funding

  1. NSF [AST-1612085]
  2. CWRU Faculty Seed Grant
  3. European Commissions Framework Programme through Marie Curie International Research Staff Exchange Scheme LACEGAL [PIRSES-GA-2010-269264]
  4. STFC/Newton Fund award [ST/M007995/1-DPI20140114]
  5. CONICYT Doctoral Fellowship Programme
  6. European Research Council [ERC-StG/716151, DEGAS-259586]
  7. Centro de Astronomia y Tecnologias Afines BASAL [PFB-06]
  8. Fondecyt Regular [1150300]
  9. Science and Technology Facilities Council [ST/L00075X/1]
  10. Royal Society through University Research Fellowship
  11. STFC
  12. Large Facilities Capital Fund of BIS
  13. QUIMAL [130008]
  14. Fondequip [AIC-57]
  15. Durham University
  16. Science and Technology Facilities Council [ST/L00075X/1, ST/P000541/1, ST/M007995/1] Funding Source: researchfish
  17. STFC [ST/M007995/1, ST/P000541/1] Funding Source: UKRI

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We study the dependence of the galaxy content of dark matter halos on large-scale environment and halo formation time using semi-analytic galaxy models applied to the Millennium simulation. We analyze subsamples of halos at the extremes of these distributions and measure the occupation functions for the galaxies they host. We find distinct differences among these occupation functions. The main effect with environment is that central galaxies (and in one model, also the satellites) in denser regions start populating lower-mass halos. A similar, but significantly stronger, trend exists with halo age, where early-forming halos are more likely to host central galaxies at lower halo mass. We discuss the origin of these trends and the connection to the stellar mass-halo mass relation. We find that, at fixed halo mass, older halos and to some extent also halos in dense environments tend to host more massive galaxies. Additionally, we see a reverse trend for the occupation of satellite galaxies where early-forming halos have fewer satellites, likely due to having more time for them to merge with the central galaxy. We describe these occupancy variations in terms of the changes in the occupation function parameters, which can aid in constructing realistic mock galaxy samples. Finally, we study the corresponding galaxy auto-and cross-correlation functions of the different samples and elucidate the impact of assembly bias on galaxy clustering. Our results can inform theoretical modeling of galaxy assembly bias and attempts to detect it in the real universe.

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