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Dark matter haloes play a fundamental role in cosmological structure formation. The most common approach to model their assembly mechanisms is through N-body simulations. In this work we present an innovative pathway to predict dark matter…

Cosmology and Nongalactic Astrophysics · Physics 2020-07-15 Mauro Bernardini , Lucio Mayer , Darren Reed , Robert Feldmann

The properties of the matter density field in the initial conditions have a decisive impact on the features of the large-scale structure of the Universe as observed today. These need to be studied via $N$-body simulations, which are…

Cosmology and Nongalactic Astrophysics · Physics 2023-06-21 Jazhiel Chacón , Isidro Gómez-Vargas , Ricardo Menchaca Méndez , José Alberto Vázquez

The mass distribution of dark matter haloes is the result of the hierarchical growth of initial density perturbations through mass accretion and mergers. We use an interpretable machine-learning framework to provide physical insights into…

Cosmology and Nongalactic Astrophysics · Physics 2022-07-06 Luisa Lucie-Smith , Susmita Adhikari , Risa H. Wechsler

The first dark matter halos form by direct collapse from peaks in the matter density field, and evidence from numerical simulations and other analyses suggests that the dense inner regions of these objects largely persist today. These halos…

Cosmology and Nongalactic Astrophysics · Physics 2019-07-24 M. Sten Delos , Margie Bruff , Adrienne L. Erickcek

We present a generalization of our recently proposed machine learning framework, aiming to provide new physical insights into dark matter halo formation. We investigate the impact of the initial density and tidal shear fields on the…

Cosmology and Nongalactic Astrophysics · Physics 2019-09-20 Luisa Lucie-Smith , Hiranya V. Peiris , Andrew Pontzen

In the standard model of cosmic structure formation, dark matter haloes form by gravitational instability. The process is hierarchical: smaller systems collapse earlier, and later merge to form larger haloes. The galaxy clusters, hosted by…

Astrophysics · Physics 2009-11-13 Carlo Giocoli , Lidia Pieri , Giuseppe Tormen

The formation of dark-matter halos from small cosmological perturbations generated in the early universe is a highly non-linear process typically modeled through N-body simulations. In this work, we explore the use of deep learning to…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-07 Toka Alokda , Cristiano Porciani

Context:Halo formation time, which quantifies the mass assembly history of dark-matter halos, directly impacts galaxy properties and evolution. Although not directly observable, it can be inferred through proxies like star formation history…

Cosmology and Nongalactic Astrophysics · Physics 2025-08-13 Atulit Srivastava , Weiguang Cui , Daniel de Andres , Jesse B. Golden-Marx , Elena Rasia , Ying Zu

We train a machine learning algorithm to learn cosmological structure formation from N-body simulations. The algorithm infers the relationship between the initial conditions and the final dark matter haloes, without the need to introduce…

Cosmology and Nongalactic Astrophysics · Physics 2018-07-02 Luisa Lucie-Smith , Hiranya V. Peiris , Andrew Pontzen , Michelle Lochner

A dark matter halo is said to have formed when at least half its mass hass been assembled into a single progenitor. With this definition, it is possible to derive a simple but useful analytic estimate of the distribution of halo formation…

Astrophysics · Physics 2009-09-29 Carlo Giocoli , Jorge Moreno , Ravi K. Sheth , Giuseppe Tormen

Protohalos, primordial regions in the initial cosmic density field that evolve into dark matter halos, are crucial for understanding cosmic structure formation. Motivated by the potential to reconstruct protohalo positions and shapes from…

Cosmology and Nongalactic Astrophysics · Physics 2026-01-12 Farnik Nikakhtar , Daisuke Nagai , Marcello Musso , Ravi K. Sheth

The protohalo patches from which halos form are defined by a number of constraints imposed on the Lagrangian dark matter density field. Each of these constraints contributes to biasing the spatial distribution of the protohalos relative to…

Cosmology and Nongalactic Astrophysics · Physics 2017-04-19 Kwan Chuen Chan , Ravi K. Sheth , Roman Scoccimarro

Dark matter halos are typically defined as spheres that enclose some overdensity, but these sharp, somewhat arbitrary boundaries introduce non-physical artifacts such as backsplash halos, pseudo-evolution, and an incomplete accounting of…

Cosmology and Nongalactic Astrophysics · Physics 2026-01-21 Ze'ev Vladimir , Calvin Osinga , Benedikt Diemer , Edgar M. Salazar , Eduardo Rozo

We use two cosmological simulations of structure formation to study the conditions under which dark matter haloes emerge from the linear density field. Our analysis focuses on matching sites of halo collapse to local density maxima, or…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-17 Aaron D. Ludlow , Cristiano Porciani

The evolution of linear initial conditions present in the early universe into extended halos of dark matter at late times can be computed using cosmological simulations. However, a theoretical understanding of this complex process remains…

Cosmology and Nongalactic Astrophysics · Physics 2024-03-26 Luisa Lucie-Smith , Hiranya V. Peiris , Andrew Pontzen , Brian Nord , Jeyan Thiyagalingam

Using a series of high-resolution N-body simulations of the concordance cosmology we investigate how the formation histories, shapes and angular momenta of dark-matter haloes depend on environment. We first present a classification scheme…

Astrophysics · Physics 2008-11-26 Oliver Hahn , Cristiano Porciani , C. Marcella Carollo , Avishai Dekel

Associating the formation sites of haloes with the maxima of the smoothed linear density field, we present non-perturbative predictions for the Lagrangian and evolved halo correlation functions that are valid at all separations. In…

Cosmology and Nongalactic Astrophysics · Physics 2021-05-05 Tobias Baldauf , Sandrine Codis , Vincent Desjacques , Christophe Pichon

We build a deep learning framework that connects the local formation process of dark matter halos to the halo bias. We train a convolutional neural network (CNN) to predict the final mass and concentration of dark matter halos from the…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-12 Luisa Lucie-Smith , Alexandre Barreira , Fabian Schmidt

The non-spherical shapes of dark matter and gas distributions introduce systematic uncertainties that affect observable-mass relations and selection functions of galaxy groups and clusters. However, the triaxial gas distributions depend on…

Cosmology and Nongalactic Astrophysics · Physics 2022-01-19 Luis Fernando Machado Poletti Valle , Camille Avestruz , David J. Barnes , Arya Farahi , Erwin T. Lau , Daisuke Nagai

We investigate the problem of predicting the halo mass function from the properties of the Lagrangian density field. We focus on a perturbation spectrum with a small-scale cut-off (as in warm dark matter cosmologies). This cut-off results…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Oliver Hahn , Aseem Paranjape
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