Statistics of galaxy mergers: bridging the gap between theory and observation

Abstract

We present a study of galaxy mergers up to $z=10$ using the Planck Millennium cosmological dark matter simulation and the {\tt GALFORM} semi-analytical model of galaxy formation. Utilising the full ($800$ Mpc)${}^3$ volume of the simulation, we studied the statistics of galaxy mergers in terms of merger rates and close pair fractions. We predict that merger rates begin to drop rapidly for high-mass galaxies ($M_{\ast }>10^{11.3}-10^{10.5}$ $M_{\odot }$ for $z=0-4$), as a result of the exponential decline in the galaxy stellar mass function. The predicted merger rates increase and then turn over with increasing redshift, by $z=3.5$, in disagreement with hydrodynamical simulations and semi-empirical models. In agreement with most other models and observations, we find that close pair fractions flatten or turn over at some redshift (dependent on the mass selection). We conduct an extensive comparison of close pair fractions, and highlight inconsistencies among models, but also between different observations. We provide a fitting formula for the major merger timescale for close galaxy pairs, in which the slope of the stellar mass dependence is redshift dependent. This is in disagreement with previous theoretical results that implied a constant slope. Instead we find a weak redshift dependence only for massive galaxies ($M_{\ast }>10^{10}$ M${}_{\odot }$): in this case the merger timescale varies approximately as $M_{\ast }^{-0.55}$. We find that close pair fractions and merger timescales depend on the maximum projected separation as $r_{\max }^{1.32}$. This is in agreement with observations of small-scale clustering of galaxies, but is at odds with the linear dependence on projected separation that is often assumed.

Accepted for publication in MNRAS

References in corpus (30)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• Introducing the Illustris Project: Simulating the coevolution of dark and visible matter in the Universe
• A primer on hierarchical galaxy formation: the semi-analytical approach
• Galaxy Merger Morphologies and Time-Scales from Simulations of Equal-Mass Gas-Rich Disc Mergers
• A fitting formula for the merger timescale of galaxies in hierarchical clustering
• The Redshift Evolution of Wet, Dry, and Mixed Galaxy Mergers from Close Galaxy Pairs in the DEEP2 Galaxy Redshift Survey
• The Structures of Distant Galaxies I: Galaxy Structures and the Merger Rate to z~3 in the Hubble Ultra-Deep Field
• Galaxy growth in the concordance $\Lambda$CDM cosmology
• A calibration of the relation between the abundance of close galaxy pairs and the rate of galaxy mergers
• A definitive merger-AGN connection at z~0 with CFIS: mergers have an excess of AGN and AGN hosts are more frequently disturbed
• A chronicle of galaxy mass assembly in the EAGLE simulation
• Observational constraints on the merger history of galaxies since $z\approx 6$: Probabilistic galaxy pair counts in the CANDELS fields
• The Structures of Distant Galaxies - III: The Merger History of over 20,000 Massive Galaxies at z < 1.2
• Galaxy And Mass Assembly (GAMA): Galaxy close-pairs, mergers, and the future fate of stellar mass
• The Millennium Galaxy Catalogue: The connection between close pairs and asymmetry; implications for the galaxy merger rate
• A consistent measure of the merger histories of massive galaxies using close-pair statistics I: Major mergers at $z<3.5$
• Galaxy And Mass Assembly (GAMA): Refining the Local Galaxy Merger Rate using Morphological Information
• Massive Close Pairs Measure Rapid Galaxy Assembly in Mergers at High Redshift
• Major Merging History in CANDELS. I. Evolution of the Incidence of Massive Galaxy-Galaxy Pairs from z=3 to z~0
• The MUSE Hubble Ultra Deep Field Survey. IX. Evolution of galaxy merger fraction since z~6
• Galaxy Mergers at z>1 in the HUDF: Evidence for a Peak in the Major Merger Rate of Massive Galaxies
• The VIMOS VLT Deep Survey: the contribution of minor mergers to the growth of L_B >= L*_B galaxies since z ~ 1 from spectroscopically identified pairs
• The host galaxies of X-ray selected Active Galactic Nuclei to z=2.5: Structure, star-formation and their relationships from CANDELS and Herschel/PACS
• Minor vs Major Mergers: The Stellar Mass Growth of Massive Galaxies from z=3 using Number Density Selection Techniques
• The ALHAMBRA survey: Accurate merger fractions by PDF analysis of photometric close pairs
• The Diffusion Approximation vs. the Telegraph Equation for Modeling Solar Energetic Particle Transport with Adiabatic Focusing. I. Isotropic Pitch-angle Scattering
• Quenching and anisotropy of hydromagnetic turbulent transport
• Connections between galaxy mergers and Starburst: evidence from local Universe
• Formation and assembly history of stellar components in galaxies as a function of stellar and halo mass
• 2MASS/SDSS Close Major-Merger Galaxy Pairs: Luminosity Functions and Merger Mass Dependence

Cited by in corpus (25)

• Born this way: thin disc, thick disc, and isotropic spheroid formation in FIRE-2 Milky-Way-mass galaxy simulations
• A direct measurement of galaxy major and minor merger rates and stellar mass accretion histories at $z<3$ using galaxy pairs in the REFINE survey
• Galaxy Mergers in the Epoch of Reionization I: A JWST Study of Pair Fractions, Merger Rates, and Stellar Mass Accretion Rates at $z=4.5-11.5$
• Morphological signatures of mergers in the TNG50 simulation and the Kilo-Degree Survey: the merger fraction from dwarfs to Milky Way-like galaxies
• VINTERGATAN IV: Cosmic phases of star formation in Milky Way-like galaxies
• The dawn of disks: unveiling the turbulent ionised gas kinematics of the galaxy population at $z\sim 4-6$ with JWST/NIRCam grism spectroscopy
• The buildup of galaxies and their spheroids: the contributions of mergers, disc instabilities and star formation
• Galaxy merger challenge: A comparison study between machine learning-based detection methods
• Massive Early-Type Galaxies in the HSC-SSP: Flux Fraction of Tidal Features and Merger Rates
• Probing the Merger Rates of Supermassive Black Holes and Galaxies with Gravitational Waves
• The molecular gas resolved by ALMA in the low-metallicity dwarf merging galaxy Haro 11
• Dynamics and spin alignment in massive, gravito-turbulent circumbinary discs around supermassive black hole binaries
• Obscured AGN enhancement in galaxy pairs at cosmic noon: evidence from a probabilistic treatment of photometric redshifts
• Probing the Delay Time of Supermassive Black Hole Binary Mergers With Gravitational Waves
• JWST + ALMA ubiquitously discover companion systems within $\lesssim 18$kpc around four $z$$\approx$3.5 luminous radio-loud AGN
• Halo Growth and Merger Rates as a Cosmological Test
• Galaxy pairs in The Three Hundred simulations: a study on the performance of observational pair-finding techniques
• The Most Massive Early-type Galaxies Exhibit Tidal Features More Frequently in Lower-density Environments
• The PAU Survey: Close galaxy pairs identification and analysis
• Galaxy pairs in The Three Hundred simulations II: studying bound ones and identifying them via machine learning
• DARKSKIES: A suite of super-sampled zoom-in simulations of galaxy clusters with self-interacting dark matter
• The JWST Emission Line Survey (JELS): The sizes and merger fraction of star-forming galaxies during the Epoch of Reionization
• Stellar Stripping and Disruption in Disks around Supermassive Black Hole Binaries: Repeating nuclear transients prior to LISA events
• On the Origins of "Hostless'' Supernovae: Testing the Faint-end Galaxy Luminosity Function and Supernova Progenitors with Events in Dwarf Galaxies
• Gas-rich dwarf galaxy multiples in the Apertif HI survey