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We develop a simple model for estimating the mass growth histories of dark matter halos. The model is based on a fit to the formation time distribution, where formation is defined as the earliest time that the main branch of the merger tree…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Carlo Giocoli , Giuseppe Tormen , Ravi K. Sheth

Merger tree codes are routinely used to follow the growth and merger of dark matter haloes in simulations of cosmic structure formation. Whereas in Srisawat et. al. we compared the trees built using a wide variety of such codes here we…

When following the growth of structure in the Universe, we propose replacing merger trees with merger graphs, in which haloes can both merge and split into separate pieces. We show that this leads to smoother mass growth and eliminates…

Astrophysics of Galaxies · Physics 2020-05-11 William J. Roper , Peter A. Thomas , Chaichalit Srisawat

We investigate seven Monte Carlo algorithms -- four old and three new -- for constructing merger histories of dark matter halos using the extended Press-Schechter (EPS) formalism based on both the spherical and ellipsoidal collapse models.…

Astrophysics · Physics 2010-12-16 Jun Zhang , Onsi Fakhouri , Chung-Pei Ma

A modified version of the extended Press-Schechter model for the growth of dark-matter haloes was introduced in two previous papers with the aim at explaining the mass-density relation shown by haloes in high-resolution cosmological…

Astrophysics · Physics 2009-11-07 A. Raig , G. Gonzalez-Casado , E. Salvador-Sole

We present a new method for calculating the merger history of matter halos in hierarchical clustering cosmologies. The linear density field is smoothed on a range of scales, these are then ordered in decreasing density and a merger tree…

Astrophysics · Physics 2015-06-24 Domingos D. C. Rodrigues , Peter A. Thomas

Merger trees harvested from cosmological $N$-body simulations encode the assembly histories of dark matter halos over cosmic time, and are a fundamental component of semi-analytical models (SAMs) of galaxy formation. The ability to compare…

Astrophysics of Galaxies · Physics 2019-02-20 Rhys J. J. Poulton , Aaron S. G. Robotham , Chris Power , Pascal J. Elahi

We have constructed merger trees for galaxies in the Illustris Simulation by directly tracking the baryonic content of subhalos. These merger trees are used to calculate the galaxy-galaxy merger rate as a function of descendant stellar…

We present a new high-resolution N-body algorithm for cosmological simulations. The algorithm employs a traditional particle-mesh technique on a cubic grid and successive multilevel relaxations on the finer meshes, introduced recursively in…

Astrophysics · Physics 2009-10-30 Andrey V. Kravtsov , Anatoly A. Klypin , Alexei M. Khokhlov

We examine the reliability of the merger trees generated for the Monte-Carlo modeling of galaxy formation. In particular we focus on the cold gas fraction predicted from the merger trees with different assumptions on the progenitor…

Astrophysics · Physics 2015-06-24 Mamoru Shimizu , Tetsu Kitayama , Shin Sasaki , Yasushi Suto

We describe a simple efficient algorithm that allows one to construct Monte-Carlo realizations of merger histories of dark matter halos. The algorithm is motivated by the excursion set model (Bond et al. 1991) for the conditional and…

Astrophysics · Physics 2009-10-30 Ravi K. Sheth , Gerard Lemson

A common approach in semi-analytic modeling of galaxy formation is to construct Monte Carlo realizations of merger histories of dark matter halos whose masses are sampled from a halo mass function. Both the mass function itself, and the…

Astrophysics of Galaxies · Physics 2017-03-22 Andrew J. Benson

For idealized (spherical, smooth) dark matter halos described by single-parameter density profiles (such as the NFW profile) there exists a one-to-one mapping between the energy of the halo and the scale radius of its density profile. The…

Astrophysics of Galaxies · Physics 2021-02-17 Turner Johnson , Andrew J. Benson , Daniel Grin

Efficiently mapping baryonic properties onto dark matter is a major challenge in astrophysics. Although semi-analytic models (SAMs) and hydrodynamical simulations have made impressive advances in reproducing galaxy observables across…

We investigate a series of galaxy properties computed using the merger trees and environmental histories from dark matter only cosmological simulations, using a semi-recurrent neural network producing self-consistent predictions of galaxy…

Cosmology and Nongalactic Astrophysics · Physics 2025-07-08 Harry George Chittenden , Jayashree Behera , Rita Tojeiro

We developed a new method to extract halo merger rates from the Millennium Simulation. First, by removing superfluous mergers that are artifacts of the FOF halo finder, we find a lower merger rate compared to previous work. The reductions…

Astrophysics · Physics 2010-11-02 S. Genel , R. Genzel , N. Bouché , T. Naab , A. Sternberg

Dark matter halo merger trees are now routinely extracted from cosmological simulations of structure formation. These trees are frequently used as inputs to semi-analytic models of galaxy formation to provide the backbone within which…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Andrew J. Benson , Stefano Borgani , Gabriella De Lucia , Michael Boylan-Kolchin , Pierluigi Monaco

We introduce the contour process to describe the geometrical properties of merger trees. The contour process produces a one-dimensional object, the contour walk, which is a translation of the merger tree. We portray the contour walk through…

Astrophysics · Physics 2015-05-13 Jaime E. Forero-Romero

The effects of spatial correlations of density fluctuations on merger histories of dark matter haloes (so-called `{\it merger trees}') are analysed. We compare the mass functions of dark haloes derived by a new method for calculating merger…

Astrophysics · Physics 2015-06-24 Masahiro Nagashima , Naoteru Gouda

We present a comprehensive series of dissipationless N-body simulations to investigate the evolution of density distribution in equal-mass mergers between dark matter (DM) halos and multicomponent galaxies. The DM halo models are…

Astrophysics · Physics 2009-11-13 Stelios Kazantzidis , Andrew R. Zentner , Andrey V. Kravtsov