A Fitting Formula for the Merger Timescale of Galaxies in Hierarchical Clustering

By C. Jiang, Yipeng Jing, A. Faltenbacher, W. Lin, Cheng Li. 2007

217 citations recorded by the source corpus.

We study galaxy mergers using a high-resolution cosmological hydro/N-body simulation with star formation and compare the measured merger timescales with theoretical predictions based on the Chandrasekhar formula. In contrast to Navarro et al., our numerical results indicate that the commonly used equation for the merger timescale given by Lacey and Cole systematically underestimates the merger timescales for minor mergers and overestimates those for major mergers. This behavior is partly explained by the poor performance of their expression for the Coulomb logarithm, ln (mpri/msat) . The two alternative forms ln (1 + mpri/msat) and ½ln[1 + (mpri/msat)2] for the Coulomb logarithm can account for the mass dependence of merger timescale successfully, but both of them underestimate the merger timescale by a factor 2. Since ln (1 + mpri/msat) represents the mass dependence slightly better, we adopt this expression for the Coulomb logarithm. Furthermore, we find that the dependence of the merger timescale on the circularity parameter ϵ is much weaker than the widely adopted power law ϵ0.78, whereas 0.94ϵ0.60 + 0.60 provides a good match to the data. Based on these findings, we present an accurate and convenient fitting formula for the merger timescale of galaxies in cold dark matter models.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c1eb436f1026a3e0b9e2f417b7d1ba8624630151

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Citations in the corpus

A unified multiwavelength model of galaxy formation (2015, methodology): “…in galactic disks, whic follows the atomic and molecular hydrogen content of the ISM, as implemented inGALFORM by Lagos et al. (2011b,a, 2012) (iii) A more accurate description of the dynamical friction timescale for galaxy mergers, calibrated against numerical s mulations (Jiang et al. 2008).”
SEMI-ANALYTIC GALAXY EVOLUTION (SAGE): MODEL CALIBRATION AND BASIC RESULTS (2016, background): “While scatter in a massdependent dynamical friction formula is inevitable, hydrodynamic simulations have since suggested there is a better generic fit than Equation 25 (Jiang et al. 2008; Jiang, Jing & Lin 2010).”
MERGERS AND BULGE FORMATION IN ΛCDM: WHICH MERGERS MATTER? (2009, methodology): “(a) Dynamical Friction: the traditional dynamical friction time, using the calibration from numerical simulations in Boylan-Kolchin et al. (2008) (see also Jiang et al. 2008).”
Erratum: From dwarf spheroidals to cD galaxies: simulating the galaxy population in a ΛCDM cosmology (2010, unknown): “It was also found to be appropriate in the N-body studies of Boylan-Kolchin et al. (2008) and Jiang et al. (2008).”
Galaxy formation theory (2010, background): “For example,Boylan-Kolchin et al. (2008) find Tdf = τdynA (MV/mV)b ln(1+ MV/mV) exp [cǫ] [ rc(E) rV ]d , (43) with A = 0.216,b = 1.3, c = 1.9 andd = 1.0 while Jiang et al. (2008) finds Tdf = τdyn 0.94ǫ0.”
Galaxy merger morphologies and time-scales from simulations of equal-mass gas-rich disc mergers (2008, result): “Also, recent comparison of N-body simulations to analytical calculations indicate that analytically-derived dynamical friction time-scales can deviate substantially from those predicted by N-body simulations (Boylan-Kolchin, Ma, & Quataert 2008; Jiang et al. 2008).”
Impact of baryon physics on dark matter structures: a detailed simulation study of halo density profiles (2010, background): “For example, the substructure may exhibit greater resistance to tidal disruption due to its deeper potential well in the presence of baryons, while at the same time the substructure will typically suffer from increased dynamical friction with the main halo (Jiang et al. 2008).”
The effects of gas on morphological transformation in mergers: implications for bulge and disc demographics (2009, background): “…trees from Wetzel, Cohn & White (2009), and implementing various approximations for a ‘merger time-scale’ (delay between halo–halo and galaxy–galaxy merger, given, for example, by some approximation to the dynamical friction time) from Boylan-Kolchin, Ma & Quataert (2008) and Jiang et al. (2008).”
The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach (2008, result): “…we have followed De Lucia & Blaizot (2007) and used ffudge = 2, which is in better agreement with recent numerical work indicating that the classical dynamical friction formulation tends to underestimate the merging times measured from simulations (Boylan-Kolchin et al. 2008; Jiang et al. 2008).”
The current status of galaxy formation (2012, methodology): “…to be those of the subhalos they belong to, and when they are no longer resolved in the cosmological simulation, or if one is only using a halo merger tree, the galaxies are merged with the central galaxy on a dynamical friction timescale (calibrated on simulations, e.g. Jiang et al., 2008).”
What determines satellite galaxy disruption (2009, methodology): “They also pointed out that, given typical satellite orbital circularity distributions (Zentner et al. 2005; Jiang et al. 2008), the detailed fits to dynamical friction infall times of Boylan-Kolchin et al. (2008) and Jiang et al. (2008) predict Cdyn = 0.06 and 0.14, respectively.”
MERGERS IN ΛCDM: UNCERTAINTIES IN THEORETICAL PREDICTIONS AND INTERPRETATIONS OF THE MERGER RATE (2010, methodology): “…disks (in e.g. their scale heights and sizes) in full cosmological simulations contributes to the fact that the major merger timescales in the calibration of Jiang et al. (2008) are significantly longer than those in high-resolution hydrodynamic simulations of individual mergers of disk galaxies.”
Galaxy evolution in groups and clusters: satellite star formation histories and quenching time-scales in a hierarchical Universe (2012, background): “…quenching process(es) may be more rapid at a given d/Rvir in a more massive host halo, this is mitigated by the fact that dynamical friction causes a satellite of a given mass to orbit to smaller d/Rvir more quickly in a lower mass host halo (Boylan-Kolchin et al. 2008; Jiang et al. 2008).”
Galaxy evolution in groups and clusters: star formation rates, red sequence fractions and the persistent bimodality (2011, background): “First, satellite dynamical infall times are shortest when the satellite-to-halo mass ratio is closest, being shorter than a Hubble time when the satellite halo to host halo mass ratio is closer than ∼0.1 (Boylan-Kolchin, Ma & Quataert 2008; Jiang et al. 2008; Wetzel & White 2010).”
Galacticus: A Semi-Analytic Model of Galaxy Formation (2010, methodology): “Dynamical Friction: Jiang (2008): This method computes merging timescales using the dynamical friction calibration of Jiang et al. (2008).”
CO-EVOLUTION OF GALACTIC NUCLEI AND GLOBULAR CLUSTER SYSTEMS (2013, background): “Since we do not know the initial distribution of globular cluster eccentricities, we take as an estimate the distribution of orbit circularity of satellite halos in cosmological simulations 4 GNEDIN ET AL. of galaxy cluster formation by Jiang et al. (2008).”