An improved prescription for merger time-scales from controlled simulations

Abstract

We compare three analytical prescriptions for merger times available from the literature to simulations of isolated mergers. We probe three different redshifts, and several halo concentrations, mass ratios, orbital circularities and orbital energies of the satellite. We find that prescriptions available in the literature significantly under-predict long timescales for mergers at high redshift. We argue that these results have not been highlighted previously either because the evolution of halo concentration of satellite galaxies has been neglected (in previous isolated merger simulations), or because long merger times and mergers with high initial orbital circularities are under-represented (for prescriptions based on cosmological simulations). Motivated by the evolution of halo concentration at fixed mass, an explicit dependence on redshift added as t_merger,modified(z) = (1+z)^0.44 t_merger to the prescription based on isolated mergers gives a significant improvement in the predicted merger times up to ~20 t_dyn in the redshift range 0<z<2. When this modified prescription is used to compute galaxy stellar mass functions, we find that it leads up to a 25 per cent increase in the number of low mass galaxies surviving at z=0, and a 10 per cent increase for more massive galaxies. This worsen the known over-prediction in the number of low mass galaxies by hierarchical models of galaxy formation.

6 pages, 3 figures, 2 tables. Replaced to match the version accepted for publication in MNRAS

References in corpus (7)

• The hierarchical formation of the brightest cluster galaxies
• The effect of galaxy mass ratio on merger--driven starbursts
• The environmental history of group and cluster galaxies in a LambdaCDM Universe
• A fitting formula for the merger timescale of galaxies in hierarchical clustering
• Properties of Galaxy Groups in the SDSS: II.- AGN Feedback and Star Formation Truncation
• The Assembly of Galaxy Clusters
• The Lives of High Redshift Mergers

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