The nearly universal merger rate of dark matter haloes in ΛCDM cosmology

By Onsi Fakhouri, Chung-Pei Ma. 2007

204 citations recorded by the source corpus.

We construct merger trees from the largest data base of dark matter haloes to date provided by the Millennium Simulation to quantify the merger rates of haloes over a broad range of descendant halo mass (10 12 ≤ M 0 ≤ 1015 M ⊙ ), progenitor mass ratio (10 -3 ≤ ξ ≤ 1), and redshift (0 ≤ z ≤ 6). We find the mean merger rate per halo, Bin, to have very simple dependence on M 0 , ξ, and z, and propose a universal fitting form for B/n that is accurate to 10-20 per cent. Overall, B/n depends very weakly on the halo mass (oc M 0 0 .08) and scales as a power law in the progenitor mass ratio (oc ξ -2 ) for minor mergers (ξ ≤ 0.1) with a mild upturn for major mergers. As a function of time, we find the merger rate per Gyr to evolve roughly as (1 + z) nm with r m = 2-2.3, while the rate per unit redshift is nearly independent of z. Several tests are performed to assess how our merger rates are affected by e.g. the time interval between Millennium outputs, binary versus multiple progenitor mergers, and mass conservation and diffuse accretion during mergers. In particular, we find halo fragmentations to be a general issue in merger tree construction from N-body simulations and compare two methods for handling these events. We compare our results with predictions of two analytical models for halo mergers based on the extended Press-Schechter (EPS) model and the coagulation theory. We find that the EPS model overpredicts the major merger rates and underpredicts the minor merger rates by up to a factor of a few.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/db03b6f7da471818a4a465db7db9bfd26ce60a16

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Citations in the corpus

A physical model for z∼ 2 dust-obscured galaxies (2009, background): “Given the increasing relative number densities of minor mergers (e.g. Fakhouri & Ma 2008; Hopkins et al. 2009), it may be that these sorts of mergers dominate bright DOG formation.”
The merger rates and mass assembly histories of dark matter haloes in the two Millennium simulations (2010, methodology): “In this paper, as in our previous work (Fakhouri & Ma 2008; McBride et al. 2009), our focus is on the merger and assembly histories of FOF haloes.”
Toy models for galaxy formation versus simulations (2013, methodology): “Similar fitting formulae with slight variations in the values of the parameters, valid in different ranges of mass and redshift, were proposed by others (Fakhouri & Ma 2008; Genel et al. 2008, 2010).”
DISSIPATION AND EXTRA LIGHT IN GALACTIC NUCLEI. IV. EVOLUTION IN THE SCALING RELATIONS OF SPHEROIDS (2008, methodology): “…progenitor halo mass of eachz = 0 halo in the simulations, integrating over analytic fits tomean merger histories from initial seed populations (Fakhouri & Ma 2008), or adopting the meanMhalo(z|Mhalo[z = zobs]) for a givenz = zobs population of halos fitted in e.g. Wechsler et al. (2002,…”
A Redshift-independent Efficiency Model: Star Formation and Stellar Masses in Dark Matter Halos at z ≳ 4 (2018, background): “150 Myr) compared to the typical timescale of major mergers (& 300 Myr, see Fakhouri & Ma 2008, 2010; Behroozi et al. 2013), mergers provide a minor contribution to the stellar mass growth.”
The eagle simulations of galaxy formation: Public release of halo and galaxy catalogues (2015, background): “This allows the identification of descendants, even in the case where most particles have been stripped and it minimises the misprediction of mergers during fly-bys (Fakhouri and Ma, 2008; Genel et al., 2009).”
THE GREATER IMPACT OF MERGERS ON THE GROWTH OF MASSIVE GALAXIES: IMPLICATIONS FOR MASS ASSEMBLY AND EVOLUTION SINCE z ≃ 1 (2009, methodology): “In an analysis of the Millennium Simulation, Fakhouri & Ma (2008), for example, find that the halo merger rate (for halo mass ratios greater than 1:3) rises by ∼30% from MDM = 10 12 to 1013.”
THE KILOPARSEC-SCALE KINEMATICS OF HIGH-REDSHIFT STAR-FORMING GALAXIES (2009, background): “Such lumps can disrupt the preferred kinematic axis of disk galaxies in the local universe (e.g., Benson et al. 2004), and their effects would likely be stronger at higher redshifts when dark matter haloes were merging more rapidly (e.g., Zentner & Bullock 2003; Fakhouri & Ma 2008).”
Accretion-driven evolution of black holes: Eddington ratios, duty cycles and active galaxy fractions (2011, methodology): “The merger rate of haloes as a function of redshift, mass ratio of the progenitors, and mass of the remnants are taken from Fakhouri & Ma (2008).”
Mass accretion rates and histories of dark matter haloes (2009, methodology): “This weak dependence on redshift is similar to that of the halo merger rates (per unit z) reported in Fakhouri & Ma (2008).”
The effects of gas on morphological transformation in mergers: implications for bulge and disc demographics (2009, methodology): “We follow a Monte Carlo population of haloes from cosmological simulations, with merger/growth trees from Fakhouri & Ma (2008).”
The cool-core bias in X-ray galaxy cluster samples - I. Method and application to HIFLUGCS (2010, unknown): “(16) This number can be compared with the predictions from full cosmological simulations (see e.g., Fakhouri & Ma 2008).”
The merger rate of galaxies in the Illustris simulation: a comparison with observations and semi-empirical models (2015, methodology): “If we had instead constructed halo merger trees using the stitching method (Fakhouri & Ma 2008), then the fit from Fakhouri, Ma & BoylanKolchin (2010) would be a better description of the resulting data.”
THE ROLE OF COLD FLOWS IN THE ASSEMBLY OF GALAXY DISKS (2008, background): “This is at odds with the merger trees of pure dark matter halos of different masses, which are statistically indistinguishable (e.g., Guo & White 2008; Stewart et al. 2008; Fakhouri & Ma 2008).”
Building merger trees from cosmological N-body simulations. Towards improving galaxy formation model (2009, background): “…Roukema et al. (1997) or FOF: Kauffmann et al. (1999); Hatton et al. (2003); Helly et al. (2003); Nagashima et al. (2005)), and more recently for subhaloes as well (using SKID (Okamoto & Habe 2000) or SUBFIND (Springel et al. 2005; De Lucia & Blaizot 2007; Fakhouri & Ma 2008)) are quite common.”
Galaxy formation theory (2010, methodology): “…utilizing N-body simulations have lead to the development of an empirical understanding of halo formation histories (Wechsler et al., 2002; van den Bosch, 2002) and halo–halo merger rates (Fakhouri and Ma, 2008a, 2009; Stewart et al., 2009; Fakhouri et al., 2010; Hopkins et al., 2010).”