Theoretical Galaxy Merger Calculations
This page is a list of theoretical calculations of galaxy merger rates, with
an aim to being complete (please email
jcohn@berkeley.edu
to add to it). Thanks to Andrew Benson, Nicolas Bouche, Sadegh Kochfar, Jorge Moreno,
Kyle Stewart and Jun Zhang for suggestions.
Subhalo galaxy mergers/merger rates
(oldest at top)
Subhalo & halo merger rate fitting formulae in boldface
 DM simulations, with or without assumptions for gas (which might
change criteria for merger)
 Makino & Hut,
http://arxiv.org/abs/astroph/9608159
cross sections and reaction rates for spherical galaxies to merge by
looking at 500 galaxy mergers in a simulation. and analytic description.
 Kolatt et al,
http://arxiv.org/abs/astroph/0010222,
"Interaction rates of darkmatter halos and subhalos",
BDM subhalos, halo and subhalo merger rates combined and compared.
60 Mpc/h side box, compares to Makino & Hut for subhalo collision rate Fig. 8
 Springel et al
http://arxiv.org/abs/astroph/0012055
"Populating a cluster of galaxiesI. Results at z=0"
assembly of a cluster, track galaxy merging explicitly within it in
DM simulation plus model for gas with history.
 De Lucia et al,
http://arxiv.org/abs/astroph/0306205
11 massive clusters and one region of mean density, dependence on
parent halo mass for subhalos, merging histories of substructures.
 Taylor & Babul,
http://arxiv.org/abs/astroph/0410049,
"The Evolution of Substructure in Galaxy, Group and Cluster Haloes III: Comparison with Simulations",
structure in 6 halos at high resolution, find substructure using SKID.
 Berrier et al,
http://arxiv.org/abs/astroph/0604506,
"Close Galaxy Counts as a Probe of Hierarchical Structure formation",
comparison in simulations of observed close pairs and merger rate.
argue number of pairs not good for merger rates but good constraint of halo
occupation distribution. 120 Mpc/h side box, 10^{9} particle mass.
 Guo & White,
http://arxiv.org/abs/0708.1814, "Galaxy Growth in the concordance
LCDM cosmology"
In MS,
dimensionless mean growth rates for galaxies as a function of redshift for
different stellar masses: growth through major mergers, all mergers,
star formation. Major merger is 1:3 or more in stellar mass.
Fig 1 merger rates, Fig 3 galaxy growth rates.
 Wang & Kauffmann,
 http://arxiv.org/abs/0801.3530, "Why are AGN found in High Mass
Galaxies"
Millennium Simulation. Why major mergers of halos based upon stellar
mass don't always lead to major mergers of subhalos with central, merger
definition based upon stellar mass.
 Mateus, http://arxiv.org/abs/0802.2720,
"Evolution of the galaxy merger rate in model universes"
2 semianalytic models using the MS, rate for number of mergers per Gyr from
z=02. rates equation 2, also fig. 3 for variation with merger definition.
 Angulo et al 2008,
http://arxiv.org/abs/0810.2177,
"The Fate of Substructures of Dark Matter Halos"
Millennium Simulation
Subhalo descendant has the majority of the 10% most bound particles from the
subhalo. Merger if descendants coincide.
Subhalo merger rate figure 5, description of mass ratios, orbits and radial distributions of subhalosubhalo mergers, merger probability since
accretion of satellite subhalo.
Rate here is rate satellites disappear (i.e., merge).
 Wetzel, Cohn & White
http://arxiv.org/abs/0810.2537
Dark matter:
major merger if ratio of infall masses is 1:3 or bigger for subhalos.
Rates as a function of redshift from ~15. Comparison to halo merger
rates. Eqn. 7 is fit to subhalo merger rates (+table 1), Halo
Merger and subhalo merger rates as function of redshift in Fig. 4
 Yang, Mo, van den Bosch
http://arxiv.org/abs/0808.2526
The subhalosatellite connection and the fate of disrupted satellite galaxies.
 Tweed et al,
http://arxiv.org/abs/0902.0679,
"Building Merger Trees from Cosmological Nbody Simulations",
AdaptaHOP vs. FoF for halo and subhalo trees.
 Hester & Tasitsiomi,
arxiv.org/abs/0902.4489,
Dark Matter Halo Mergers I: Dependence on Environment & Redshift Evolution
Mergers in halos with more satellites (similar to Wetzel et al
http://arxiv.org/abs/0810.3650)
Fig. 1 Halo merger rate with redshift, Fig. 1, subhalo merger
rates. Fig. 5 how subhalo number changes merger rate., Fig. 6 Merger rates.

(merger definition issues) Wetzel and White,
http://arxiv.org/abs/0907.0702,
"What determines satellite galaxy disruption?",
uses observations to say when a dark matter subhalo should be considered
as merged with the central halo, but matching counts/clustering at redshift
~0 and 1. Also gives a corresponding dynamical friction model calibration.
 (merger definition issues) Hopkins et al 2010,
http://arxiv.org/abs/1004.2708, Mergers in LambdaCDM: Uncertainties in Theoretical Predictions and Interpretations of the Merger Rate: comparing different
defintions of mergers (stellar mass, baryons, cold gas) in different approaches, and some corrections needed in some approaches for convergence with data.

Mergers, simulations with gas included, mostly same group over time.
 Murali et al,
http://arxiv.org/abs/astroph/0106282
"The growth of galaxies in cosmological simulations of structure
formation,"
mergers and smooth accretion contributions for ~L* systems.
redshift 2 to 0. boxes 5011 Mpc/h sides.
 Maller
http://arxiv.org/abs/astroph/0509474
cosmological hydro simulation. merger rates for galaxies. [22 mpc/h box],
figure 7.

Simha et al
http://arxiv.org/abs/0809.2999, "Assembly histores of central and
satellite galaxies"
mergers broken down into parent populations/sources
 Keres et al
http://arxiv.org/abs/0809.1430, "Galaxies in a simulated LCDM
Universe I: cold mode and hot cores", satellites keep gaining
mass after infall, at high redshift, relative to centrals.
 Keres et al
http://arxiv.org/abs/0901.1880, "Galaxies in a simulated LCDM
Universe II: Observable Properties and Constraints on Feedback"
 Hopkins et al,
http://arxiv.org/abs/0906.5357,
"Mergers and Bulge Formation in LambdaCDM: Which Mergers Matter?",
semiempirical models,
predicts galaxy merger rates and contributions to bulge growth as functions of merger mass, redshift, and mass ratio. uses empirical halo occupation constraints to identify mergers, together with highresolution simulations to quantify how mergers with different properties contribute to the bulge population. compares
to observational constraints, gives
fitting functions for merger rates and contributions to bulge growth.
 Hopkins et al, "A Cosmological Framework for the CoEvolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: I. Galaxy Mergers & Quasar Activity "
http://arxiv.org/abs/0706.1243
know subhalos are there, calculate how long it takes for them to hit
the center, use range of methods and range of subhalo distributions
people have. Efficiency of major mergers, fig. 2, as fn of Mhalo,
merger fraction as function of host halo mass, fig 6, merger efficiency for satsat, censat etc., fig 4.


 Wetzel & White, http://arxiv.org/abs/0907.0702,
What determins satellite galaxy disruption?
calibration of dynamical infall time from cosmological simulations

Stewart, Bullock, Barton, Wechsler
http://arxiv.org/abs/0811.1218,
"Galaxy and Dark Matter Halo mergers"
Dark matter simulations.
Merger if subhalo loses >90% of mass.
Take halos, get halo merger rates, associate halos with galaxies to get
galaxy merger rate.
Galaxy major merger fraction assuming halo mergers give galaxy mergers
in 11??
 Khochfar & Silk,
http://xxx.uniaugsburg.de/abs/0809.1734,
"Dry Mergers: A Crucial Test for Galaxy Formation,"
The dry merger rate and the consequences of feedback on it.
Especially the mass ratio of merging galaxies.

Khochfar & Burkert,
http://xxx.uniaugsburg.de/abs/astroph/0105383,
"Redshift Evolution of the Merger Fraction of Galaxies in CDM Cosmologies"
Galaxy merger rates in LCDM SAM from EPS merger trees + dynamical friction.
Shows the dependency of the powerlaw slope as a function of environment, mass resolution and mass ratio
 Kitzbichler & White?

Benson et al,
arXiv:astroph/0108217,
""The effects of photoionization on galaxy formation  I. Model and results at z=0"
The evolution of the galaxies is calculated using a semianalytical model, including a detailed treatment of the effects of tidal stripping and dynamical friction on satellite galaxies orbiting inside larger dark matter haloes
 Dynamical friction simulation measurements
 http://arxiv.org/abs/0902.3734 Jiang, Jing & Lin,
"Influence of baryonic physics on the merger timescale of galaxies in Nbody/hydrodynamical simulations"
Merger timescale little affected by the star formation recipes, except for the satellites in nearly radial orbits (22 percent higher timescale in the lower stellar mass case). Radial orbits only a small part of the satellites' orbits.
 BoylanKolchin, Ma, Quataert,
http://arxiv.org/abs/0707.2960
"Dynamical Friction and Merging Galaxy Timescales"
collide DM halos to get merging timescales,
dynam friction predictions for merging timescales, systematically shorter than those found in simulations, give fitting function.
 Jiang++08,
http://arxiv.org/abs/0707.2628,
"A fitting formula for the merger timescale of galaxies in hierarchical clustering",
Galaxy mergers in hydro/Nbody simulation with star formation, compare
measured merger timescales with theoretical predictions based on the Chandrasekhar formula. Based on these findings, we present an accurate and convenient fitting formula for the merger timescale of galaxies in cold dark matter models.
 Taylor & Babul,
arXiv:astroph/0012305
"The Dynamics of Sinking Satellites around Disk Galaxies: A Poor Man's Alternative to HighResolution Numerical Simulations"
Dynamical friction calculations for satellites and orbital parameters etc.
 Metcalf & Madau??
Halo merger rates vs. subhalo merger rates
(most recent first, long history here)
 Neistein & Maccio
http://arxiv.org/abs/0903.1640,
Universal Merging Histories of DarkMatter Haloes,
Statistical properties such as mergerrates and mainprogenitor histories,
global fit can be used to transform mergertrees extracted
from a given Nbody simulation into a different cosmology or mass resolution.
 Genel et al,
http://arxiv.org/abs/0812.3154
The halo merger rate in the Millennium Simulation and implications for observed galaxy merger fractions
Halo Merger rate formulae, section 3
 Fakhouri & Ma,
http://arxiv.org/abs/0808.2471,
"Environmental Dependence of Dark Matter Halo Growth I: Halo Merger Rates"
Dependence of the merger rate of haloes on their surrounding environment,
using different definitions of environment.
 Stewart et alhttp://arxiv.org/abs/0711.5027,
"Merger Histories of Galaxy Halos and Implications for Disk Survival",
halo merger fractions for
10^1110^13 Msun halos in the past t=012 Gyrs.
Emphasis on disk survival. Uses 2 different definitions of
merger mass ratio to compare and contrast. Main results:
Fig 5 and Fig 8 (Fig 8 in appendix) have fraction of halos (not subhalos)
having a major merger since a given time
 Fakhouri & Ma,
http://arxiv.org/abs/0710.4567,
"The Nearly Universal Merger Rate of Dark Matter Haloes in LambdaCDM Cosmology",
Millennium simulation, descendant halo mass (1e12 < M0 < 1e15 Msun), progenitor mass ratio (1e3 < xi < 1), and redshift (0 < z < 6).
(section 4 has results).
Equation 12 is fitting function to Halo merger rates.
 Neistein, Dekel
http://arxiv.org/abs/0708.1599,
Constructing Merger Trees that Mimic NBody Simulations,
Accurate analytic timeinvariant approximations for the main progenitor
accretion history and for halo merger rates.
 Wetzel, Schulz, Holz & Warren
http://arxiv.org/abs/0706.0518
Close Pairs as Proxies for Galaxy Cluster Mergers,
DM simulations, merger timescales, merger rates from z ~ 01, environmental
dependence (cluster sized halos).
 Cohn & White,
http://arxiv.org/abs/0706.0208,
"Dark matter halo abundances, clustering and assembly histories at high
redshift"
includes comparison with EPS predictions for progenitor masses at z=10.
 Li et al,
http://arxiv.org/abs/astroph/0510372,
"On The Assembly History of Dark Matter Haloes",
mass assembly history of dark matter halos using eps, simulations and pinocchio.
slow and fast mass accretion rates.
 Gottloeber, Klypin, Kravtsov
http://arxiv.org/abs/astroph/0004132,
"Merging history as a function of halo environment",
scaling laws for merger rates, comparison of different environments.
 [ lots in here]
 Tormen,
http://arxiv.org/abs/astroph/9802290,
"The Assembly of Matter in Galaxy Clusters"
Merging history of dm halos that end up in rich clusters. Scale free sims.
 Lacey & Cole,
http://arxiv.org/abs/astroph/9402069
"Merger rates in hierarchical models of galaxy formation. II: Comparison with Nbody simulations"
Classic EPS derivation, compare to simulations.
 Kauffmann & White,
MNRAS 1993, 261, 921
"The merging history of dark matter haloes in a hierarchical universe".
algorithm for merging history trees, comparison to simulations.
(most recent first, long history here)
 Neistein & Dekel,
http://arxiv.org/abs/0802.0198
"Merger rates of DarkMatter halos"
EPS analytic merger rates. new way to do trees.
 Zhang, Ma, Fakhouri,
http://arxiv.org/abs/0801.3459,
"Conditional Mass Functions and Merger Rates of Dark Matter Halos in the Ellipsoidal Collapse Model ",
Analytic merger rates, generalizing EPS
 Benson,
2008,MNRAS 388, 1361,
"Constraining cold dark matter halo merger rates using the coagulation equations",
 Neistein and Dekel,
http://arxiv.org/abs/0708.1599,
Constructing Merger Trees that Mimic NBody Simulations,
Accurate analytic timeinvariant approximations for the main progenitor accretion history and for halo merger rates.
equation 9 is halo mass growth rate, eqn. 12 is merger rate
 Giocoli et al, 2007,
http://arxiv.org/abs/astroph/0611221,
"An improved model for the formation times of dark matter haloes",
estimates of halo formation based on ellipsoidal collapse model.
 Benson, Kamionkowsi,Hassani,
http://arxiv.org/abs/astroph/0407136,
"SelfConsistent Theory of Halo Mergers,"
for power law spectra can reproduce halo abundance, general considerations.
 Miller?
 Percival & Miller,
http://arxiv.org/abs/astroph/9906204,
"Cosmological Evoultion & Hierarchical Galaxy Formation"
rates at which DM halos merge to form higher mass systems, compare to
Nbody and Monte Carlo
 Sheth and Lemson
http://arxiv.org/abs/astroph/9805322,
 [ lots in here]
 Kitayama & Suto,
 Lacey & Cole,
http://arxiv.org/abs/astroph/9402069
"Merger rates in hierarchical models of galaxy formation. II: Comparison with Nbody simulations"
Classic EPS derivation.
 Bond & Myers 1991
 Bower 1991
 Thacker, Scannapieco & Couchman,
http://arxiv.org/abs/0706.0518
cross correlation of mergers (mergers = mass gain of >30%), enhanced clustering for mergers at short distances
compared to other objects above some luminosity.
Also see
http://arxiv.org/abs/0706.0518, (Thacker, Scannapieco, Couchman,
Richardson).
Redshift, Luminosity and Selection Dependence for QSO's, again
with merger enhancement.
 Wetzel, Cohn & White
http://arxiv.org/abs/0810.3650,
Clustering and Hosts of Galaxy Mergers at High Redshift
DM simulations, Mergers 1:3 in infall mass, HOD for mergers (recently
merged subhalos tend to be in halos with more satellites)
 Bonoli,Shankar, White,Springel,Wyithe
http://arxiv.org/abs/0909.0003,
On merger bias and the clustering of quasars
Millennium simulations, mergers 1:4 of stellar mass, recent mergers have
different clustering, for z ~25, bounded by 2030%.
Please email jcohn@berkeley.edu
to add correct/references.
Last modified: Fri Mar 20 14:11:39 PDT 2009