Journal Article

Universal merger histories of dark-matter haloes

Eyal Neistein, Andrea V. Macciò and Avishai Dekel

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 403, issue 2, pages 984-995
Published in print April 2010 | ISSN: 0035-8711
Published online March 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.16174.x
Universal merger histories of dark-matter haloes

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We study merger histories of dark-matter haloes in a suite of N-body simulations that span different cosmological models. The simulated cases include the up-to-date Wilkinson Microwave Anisotropy Probe 5 cosmology and other test cases based on the Einstein–deSitter cosmology with different power spectra. We provide a robust fitting function for the conditional mass function of progenitor haloes of a given halo. This fit is valid for the different cosmological models and for different halo masses and redshifts, and it is a significant improvement over earlier estimates. Based on this fit, we develop a simple and accurate technique for transforming the merger history of a given simulated halo into haloes of different mass, redshift and cosmology. Other statistics such as main-progenitor history and merger rates are accurately transformed as well. This method can serve as a useful tool for studying galaxy formation. It is less sensitive to the low accuracy of the fit at small time-steps, and it can thus replace the more elaborate task of construction Monte Carlo realizations. As an alternative approach, we confirm the earlier finding by Neistein & Dekel that the main-progenitor follows a log-normal distribution. This property of merger trees allows us to better capture their behaviour as a function of time and descendant mass, but a broader suite of simulations is required for evaluating the dependence of the log-normal parameters on the cosmological model.

Keywords: gravitation; galaxies: formation; galaxies: haloes; cosmology: theory; dark matter

Journal Article.  9286 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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