Dynamical friction and galaxy merging time-scales

By M. Boylan-Kolchin, Chung-Pei Ma, E. Quataert. 2007

340 citations recorded by the source corpus.

The time-scale for galaxies within merging dark matter haloes to merge with each other is an important ingredient in galaxy formation models. Accurate estimates of merging time-scales are required for predictions of astrophysical quantities such as black hole binary merger rates, the build-up of stellar mass in central galaxies and the statistical properties of satellite galaxies within dark matter haloes. In this paper, we study the merging time-scales of extended dark matter haloes using N-body simulations. We compare these results to standard estimates based on the Chandrasekhar theory of dynamical friction. We find that these standard predictions for merging time-scales, which are often used in semi-analytic galaxy formation models, are systematically shorter than those found in simulations. The discrepancy is approximately a factor of 1.7 for M sat /M host ≈ 0.1 and becomes larger for more disparate satellite-to-host mass ratios, reaching a factor of ∼3.3 for M sat /M host ≈ 0.01. Based on our simulations, we propose a new, easily implementable fitting formula that accurately predicts the time-scale for an extended satellite to sink from the virial radius of a host halo down to the halo's centre for a wide range of M sat /M host and orbits. Including a central bulge in each galaxy changes the merging time-scale by ≤10 per cent. To highlight one concrete application of our results, we show that merging time-scales often used in the literature overestimate the growth of stellar mass by satellite accretion by ≈40 per cent, with the extra mass gained in low mass ratio mergers.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/1111247f83b7649b839225f2e3a82bcd251bf96a

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Citations in the corpus

The nearly universal merger rate of dark matter haloes in ΛCDM cosmology (2007, background): “This behaviour is not too surprising because merging haloes oscillate in and out of their respective virial radii before dynamical friction brings them into virial equilibrium (typically on timescales of a few Gyrs; see, e.g., Boylan-Kolchin et al. 2008).”
THE NON-CAUSAL ORIGIN OF THE BLACK-HOLE–GALAXY SCALING RELATIONS (2010, methodology): “The averaging process described above will only apply to this second category of halos (the ones that actually merge), we then adopt the dynamical friction formula presented in Boylan-Kolchin et al. (2008) to compute the fate of a halo.”
Star formation in semi-analytic galaxy formation models with multiphase gas (2015, methodology): “To estimate this merger timescale we use a variant of the Chandrasekhar formula from Boylan-Kolchin et al. (2008).”
Red Galaxy Growth and the Halo Occupation Distribution (2008, background): “Semianalytic models and simulations with rapid growth of massive galaxies may be overestimating the ability of halo mergers to funnel stellar mass into central galaxies (e.g., Taylor & Babul 2001; Benson et al. 2003; Taffoni et al. 2003; Boylan-Kolchin et al. 2008).”
THE ASSEMBLY OF SUPERMASSIVE BLACK HOLES AT HIGH REDSHIFTS (2008, background): “Boylan-Kolchin et al. (2008) give a fitting formula for the merger time based on numerical simulations.”
Erratum: From dwarf spheroidals to cD galaxies: simulating the galaxy population in a ΛCDM cosmology (2010, neutral): “It was also found to be appropriate in the N-body studies of Boylan-Kolchin et al. (2008) and Jiang et al. (2008).”
Are Brightest Halo Galaxies Central Galaxies (2010, background): “Another effect that may cause the SAMs to underpredict fBNC is the fact that they often adopt dynamical friction time-scales that are too short (Boylan-Kolchin et al. 2008; Wetzel & White 2010).”
Star formation and AGN activity in SDSS cluster galaxies (2009, background): “From N-body simulations, Boylan-Kolchin et al. (2008) find that in orderfo the dynamical friction time-scale to be of the order of< 5 Gyr, the mass ratio between the satellite and the host halo needs to belarge, & 0.1, and the merger orbit needs to be highly eccentric.”
The effect of mass ratio on the morphology and time-scales of disc galaxy mergers: Effect of mass ratio on merger morphology (2009, background): “The minor G3-G1 merger time-scales for sub-parabolic orbits (∼ 4 Gyr) appear to be more consistent with Boylan-Kolchin et al. (2008) dynamical friction time-scale for mergers with similar orbits and mass ratios (∼ 3.5-4.5 Gyr).”
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).”
Physical Models of Galaxy Formation in a Cosmological Framework (2014, methodology): “Many SAMs use refined versions of this formula based on numerical simulations (e.g. Boylan-Kolchin et al. 2008).”