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We introduce and apply a new approach to probe the response of galactic stellar haloes to the interplay between cosmological merger histories and galaxy formation physics. We perform dark matter-only, zoomed simulations of two Milky…

Astrophysics of Galaxies · Physics 2022-01-21 Martin P. Rey , Tjitske K. Starkenburg

We present a comprehensive analysis of the shape of dark matter (DM) halos in a sample of 25 Milky Way-like galaxies in TNG50 simulation. Using an Enclosed Volume Iterative Method (EVIM), we infer an oblate-to-triaxial shape for the DM halo…

Using our rich observations within the Milky Way to better understand galaxy evolution requires understanding what the Milky Way looks like "as a galaxy" -- that is, its "true" shape and abundance profiles (unskewed by observational…

Astrophysics of Galaxies · Physics 2025-07-24 Gail Zasowski , Julie Imig , Hayley Coluccio

From the IllustrisTNG-50 simulation, a sample of 836 central disk galaxies with tiny stellar halos is chosen to study the inherent evolution of galaxies driven by nature. These galaxies are classified as compact, normal, or extended by…

Astrophysics of Galaxies · Physics 2024-09-25 Hong-Chuan Ma , Min Du , Luis C. Ho , Ming-jie Sheng , Shihong Liao

The stellar populations of the stellar halo and of the thick disk of the Milky Way reveal much about the merging history that our Galaxy, a typical large disk galaxy, has experienced. Our current understanding, described here, implies a…

Astrophysics · Physics 2007-05-23 Rosemary F. G. Wyse

Mergers and the spin of the dark matter halo are factors traditionally believed to determine the morphology of galaxies within a $\Lambda$CDM cosmology. We study this hypothesis by considering approximately 18,000 central galaxies at $z=0$…

We study the evolution of stellar mass in galaxies as a function of host halo mass, using the "MPA" and "Durham" semi-analytic models, implemented on the Millennium Run simulation. The results from both models are similar. We find that…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 Idit Zehavi , Santiago Patiri , Zheng Zheng

In the $\Lambda$-Cold Dark Matter model of the Universe, galaxies form in part through accreting satellite systems. Previous work have built an understanding of the signatures of these processes contained within galactic stellar halos. This…

Aims: We study the effects of the cosmological assembly history on the chemical and dynamical properties of the discs of spiral galaxies as a function of radius. Methods: We make use of the simulated Milky-Way mass, fully-cosmological…

Astrophysics of Galaxies · Physics 2016-02-03 T. Ruiz-Lara , C. G. Few , B. K. Gibson , I. Pérez , E. Florido , I. Minchev , P. Sánchez-Blázquez

Massive satellite accretions onto early galactic disks can lead to the deposition of dark matter in disk-like configurations that co-rotate with the galaxy. This phenomenon has potentially dramatic consequences for dark matter detection…

Astrophysics of Galaxies · Physics 2011-02-11 Chris W. Purcell , James S. Bullock , Manoj Kaplinghat

Disk galaxies are common in our universe and this is a source of concern for hierarchical formation models like LCDM. Here we investigate this issue as motivated by raw merger statistics derived for galaxy-size dark matter halos from LCDM…

Astrophysics · Physics 2015-05-13 James S. Bullock , Kyle R. Stewart , Chris W. Purcell

If the favored hierarchical cosmological model is correct, then the Milky Way system should have accreted ~100-200 luminous satellite galaxies in the past \~12 Gyr. We model this process using a hybrid semi-analytic plus N-body approach…

Astrophysics · Physics 2008-11-26 James S. Bullock , Kathryn V. Johnston

A key unresolved question is the role that galaxy mergers play in driving stellar mass growth over cosmic time. Recent observational work hints at the possibility that the overall contribution of `major' mergers (mass ratios $\gtrsim$1:4)…

Astrophysics of Galaxies · Physics 2017-09-07 G. Martin , S. Kaviraj , J. E. G. Devriendt , Y. Dubois , C. Laigle , C. Pichon

As stars traverse the Milky Way, their orbits evolve through perturbations that alter their orbital radii. These changes arise from two mechanisms: churning, which modifies angular momentum, and blurring, which induces eccentric orbits…

Astrophysics of Galaxies · Physics 2025-12-18 M. L. L. Dantas , R. Smiljanic , R. S. de Souza , P. B. Tissera , L. Magrini

The history of gas assembly in early galaxies is reflected in their complex kinematics. While a considerable fraction of galaxies at z~5 are consistent with rotating disks, current studies indicate that the dominant galaxy assembly…

It is known observationally that the major axes of galaxy clusters and their brightest cluster galaxies are roughly aligned with each other. To understand the origin of the alignment, we identify 40 cluster-sized dark matter (DM) haloes…

Cosmology and Nongalactic Astrophysics · Physics 2020-01-08 Taizo Okabe , Takahiro Nishimichi , Masamune Oguri , Sébastien Peirani , Tetsu Kitayama , Shin Sasaki , Yasushi Suto , Christophe Pichon , Yohan Dubois

Stellar halos in early-type galaxies (ETGs) are shaped by their accretion and merger histories. We use a sample of 1114 ETGs in the TNG100 simulation with stellar masses $10^{10.3}\leq M_{*}/M_\odot\leq 10^{12}$, selected at z=0 within the…

Astrophysics of Galaxies · Physics 2021-03-17 C. Pulsoni , O. Gerhard , M. Arnaboldi , A. Pillepich , V. Rodriguez-Gomez , D. Nelson , L. Hernquist , V. Springel

As galaxies form hierarchically, larger satellites may accrete alongside smaller companions in group infall events. This coordinated accretion is likely to have left signatures in the Milky Way's stellar halo at the present day. Our goal is…

Astrophysics of Galaxies · Physics 2025-08-20 Thomas M. Callingham , Amina Helmi

We present an in-depth analysis of gas morphologies for a sample of 25 Milky Way-like galaxies from the IllustrisTNG TNG50 simulation. We constrain the morphology of cold, warm, hot gas, and gas particles as a whole using a Local Shell…

The hierarchical model of galaxy evolution suggests that the impact of mergers is substantial on the intricate processes that drive stellar assembly within a galaxy. However, accurately measuring the contribution of accretion to a galaxy's…