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We propose a new method to recover the cosmological initial conditions of the presently observed galaxy distribution, which can serve to run constrained simulations of the Local Universe. Our method, the Reverse Zeldovich Approximation…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Timur Doumler , Yehuda Hoffman , Helene Courtois , Stefan Gottloeber

The Reverse Zeldovich Approximation (RZA) is a reconstruction method which allows to estimate the cosmic displacement field from galaxy peculiar velocity data and to constrain initial conditions for cosmological simulations of the Local…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Timur Doumler , Helene Courtois , Stefan Gottloeber , Yehuda Hoffman

Peculiar velocities, obtained from direct distance measurements, are data of choice to achieve constrained simulations of the Local Universe reliable down to a scale of a few Megaparsecs. Unlike redshift surveys, peculiar velocities are…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-17 Jenny G. Sorce , Helene M. Courtois , Stefan Gottloeber , Yehuda Hoffman , R. Brent Tully

We present and test a new method for the reconstruction of cosmological initial conditions from a full-sky galaxy catalogue. This method, called ZTRACE, is based on a self-consistent solution of the growing mode of gravitational…

Astrophysics · Physics 2009-10-31 P. Monaco , G. Efstathiou

Numerical simulations are a key tool to decipher the dynamics of gravitation. Yet, they fail to spatially reproduce the Universe we observe, limiting comparison between observations and simulations to a statistical level. This is highly…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-04 Aurélien Valade , Noam Libeskind , Daniel Pomarède , Richard Stiskalek , Yehuda Hoffman , Stefan Gottlöber , R. Brent Tully

Reconstructing the initial conditions of the Universe from late-time observations has the potential to optimally extract cosmological information. Due to the high dimensionality of the parameter space, a differentiable forward model is…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-19 Adrian E. Bayer , Chirag Modi , Simone Ferraro

Galaxy clusters are excellent cosmological probes provided that their formation and evolution within the large scale environment are precisely understood. Therefore studies with simulated galaxy clusters have flourished. However detailed…

Cosmology and Nongalactic Astrophysics · Physics 2018-07-04 Jenny G. Sorce

Reconstructing the density fluctuations in the early Universe that evolved into the distribution of galaxies we see today is a challenge of modern cosmology [ref.]. An accurate reconstruction would allow us to test cosmological models by…

Astrophysics · Physics 2015-06-24 Uriel Frisch , Sabino Matarrese , Roya Mohayaee , Andrei Sobolevski

I present a new approach to recover the primordial density fluctuations and the cosmic web structure underlying a galaxy distribution. The method is based on sampling Gaussian fields which are compatible with a galaxy distribution and a…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Francisco-Shu Kitaura

We present a generalized version of the Path Interchange Zel'dovich Approximation (PIZA; Croft and Gaztanaga 1997; hereafter CG97), which may be used to reconstruct density and velocity fields from realistic galaxy redshift surveys. The…

Astrophysics · Physics 2007-05-23 Helen E. M. Valentine , Will Saunders , Andy Taylor

A reconstruction method for recovering the initial conditions of the Universe starting from the present galaxy distribution is presented which guarantees uniqueness of solutions. We show how our method can be used to obtain the peculiar…

Astrophysics · Physics 2007-05-23 Roya Mohayaee , Brent Tully , Uriel Frisch

Constrained cosmological simulations play an important role in modelling the local Universe, enabling investigation of the dark matter content of local structures and their formation. We introduce an internal method for quantifying the…

Cosmology and Nongalactic Astrophysics · Physics 2024-10-29 Richard Stiskalek , Harry Desmond , Julien Devriendt , Adrianne Slyz

We present a method for populating dark matter simulations with haloes of mass below the resolution limit. It is based on stochastically sampling a field derived from the density field of the halo catalogue, using constraints from the…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Sylvain de la Torre , John A. Peacock

We present a refined deep-learning-based method to reconstruct the three-dimensional dark matter density, gravitational potential, and peculiar velocity fields in the Zone of Avoidance (ZOA), a region near the galactic plane with limited…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-07 Alexandra Dupuy , Donghui Jeong , Sungwook E. Hong , Ho Seong Hwang , Juhan Kim , Hélène M. Courtois

We present a methodology for constructing modified gravity (MG) constrained simulations of the local Universe using positions and peculiar velocities from the CosmicFlows data set. Our analysis focuses on the following MG models: the normal…

Cosmology and Nongalactic Astrophysics · Physics 2023-02-27 Krishna Naidoo , Wojciech A. Hellwing , Maciej Bilicki , Noam Libeskind , Simon Pfeifer , Yehuda Hoffman

We present a generalized version of the Path Interchange Zel'dovich Approximation (PIZA), for use with realistic galaxy redshift surveys. PIZA is a linear particle-based Lagrangian method which uses the present day positions of galaxies to…

Astrophysics · Physics 2007-05-23 Helen Valentine , Will Saunders , Andy Taylor

This paper combines observational datasets and cosmological simulations to generate realistic numerical replicas of the nearby Universe. These latter are excellent laboratories for studies of the non-linear process of structure formation in…

We conduct simulations of $\sim$kpc-scale cool clouds in the circumgalactic medium (CGM), using initial conditions sampled from a highly resolved cosmological magneto-hydrodynamical zoom-in of a Milky Way-like galaxy. We select ten distinct…

Astrophysics of Galaxies · Physics 2026-03-02 Rahul Ramesh , Dylan Nelson , Drummond Fielding , Marcus Brüggen

We explore the potential of cross-correlating galaxies and peculiar velocities on non-linear scales to enhance cosmological constraints. Leveraging the \textsc{AbacusSummit} simulation suite and the halo occupation distribution (HOD)…

We develop a machine learning approach to reconstructing the cosmological initial conditions from late-time dark matter halo number density fields in redshift space, with the goal of improving sensitivity to cosmological parameters, and in…

Cosmology and Nongalactic Astrophysics · Physics 2025-08-15 Jelte Bottema , Thomas Flöss , P. Daniel Meerburg
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