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The structure and evolution of the stellar velocity ellipsoid plays an important role in shaping galaxies undergoing bar driven secular evolution and the eventual formation of a boxy/peanut bulge such as present in the Milky Way. Using…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Kanak Saha , Daniel Pfenniger , Ronald E. Taam

More than 50 per cent of present-day massive disc galaxies show a rotating stellar bar. Their formation and dynamics have been widely studied both numerically and observationally. Although numerical simulations in the $\Lambda$CDM…

Astrophysics of Galaxies · Physics 2022-01-17 Ornela F. Marioni , Mario G. Abadi , Stefan Gottlöber , Gustavo Yepes

Does the environment of a galaxy directly influence the kinematics of its bar? We present observational evidence that bars in high-density environments exhibit significantly slower rotation rates than bars in low-density environments.…

Astrophysics of Galaxies · Physics 2026-03-18 Natalia Puczek , Tobias Géron , Rebecca J. Smethurst , Chris J. Lintott

We re-analyse photometric near-infrared data in order to investigate why it is so hard to get a consensus for the shape and density law of the bulge, as seen from the literature. To solve the problem we use the Besancon Galaxy Model to…

Astrophysics of Galaxies · Physics 2015-06-03 Annie C. Robin , Douglas J. Marshall , Mathias Schultheis , Celine Reyle

Context. Bars are elongated structures developed by a large fraction of disk galaxies in their central few kiloparsecs. However, the bar formation process is still not fully understood, particularly the role played by the galaxy environment…

Astrophysics of Galaxies · Physics 2026-01-14 Virginia Cuomo , J. Alfonso L. Aguerri , Lorenzo Morelli , Nelvy Choque-Challapa , Stefano Zarattini

Understanding the role of galactic scale bars in disk galaxy evolution requires detailed measurements of bar properties across galaxies hosting bars at many redshifts. We present measurements of bar lengths and widths in a sample of 8230…

I discuss results from the COSMOS survey, showing that the fraction of disc galaxies that is barred decreases considerably with look-back time from z ~ 0.2 to z ~ 0.8. This decrease is more important for small mass and low luminosity…

Astrophysics · Physics 2008-02-04 E. Athanassoula

We study the dynamical interactions of mass systems in equilibrium under their own gravity that mutually exert and experience gravitational forces. The method we employ is to model the dynamical evolution of two isolated bars, hosted within…

Astrophysics of Galaxies · Physics 2017-07-12 F. Garzon , M. Lopez-Corredoira

Bar structures can form internally due to the instability of their host galaxies or externally due to perturbations from other galaxies. We systematically quantify the growth timescales ($\tau_\mathrm{bar}$) of bars formed through these two…

Astrophysics of Galaxies · Physics 2025-07-01 Yirui Zheng , Juntai Shen , Xufen Wu , Bin-Hui Chen

We compute the chemical evolution of the Galactic bulge in the context of an inside-out model for the formation of the Milky Way. The model contains updated stellar yields from massive stars. The main purpose of the paper is to compare the…

Astrophysics · Physics 2009-11-13 Silvia K. Ballero , Francesca Matteucci , Livia Origlia , R. Michael Rich

Using $N$-body simulations we study the buckling instability in a galactic bar forming in a Milky Way-like galaxy. The galaxy is initially composed of an axisymmetric, exponential stellar disk embedded in a spherical dark matter halo. The…

Astrophysics of Galaxies · Physics 2019-09-04 Ewa L. Lokas

Recent data from the VVV survey have strengthened evidence for a structural change in the Galactic bulge inwards of |l|<=4 deg. Here we show with an N-body barred galaxy simulation that a boxy bulge formed through the bar and buckling…

Astrophysics of Galaxies · Physics 2015-06-03 Ortwin Gerhard , Inma Martinez-Valpuesta

Galaxy models have long predicted that galactic bars slow down by losing angular momentum to their postulated dark haloes. When the bar slows down, resonance sweeps radially outwards through the galactic disc while growing in volume,…

Astrophysics of Galaxies · Physics 2023-08-04 Rimpei Chiba , Ralph Schönrich

Secular evolution gradually shapes galaxies by internal processes, in contrast to early cosmological evolution which is more rapid. An important driver of secular evolution is the flow of gas from the disk into the central regions, often…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 Johan H. Knapen

One third of present-day spirals host optically visible strong bars that drive their dynamical evolution. However, the fundamental question of how bars evolve over cosmological times has yet to be addressed, and even the frequency of bars…

We study the distinction and quantification of chaotic and regular motion in a time-dependent Hamiltonian barred galaxy model. Recently, a strong correlation was found between the strength of the bar and the presence of chaotic motion in…

Chaotic Dynamics · Physics 2015-03-20 T. Manos , T. Bountis , Ch. Skokos

Bulges are of different types, morphologies and kinematics, from pseudo-bulges, close to disk properties (Sersic index, rotation fraction, flatenning), to classical de Vaucouleurs bulges, close to elliptical galaxies. Secular evolution and…

Astrophysics of Galaxies · Physics 2009-01-21 F. Combes

We discuss the evolution of a disc galaxy due to the formation of a bar and, subsequently, a peanut. After the formation stage there is still considerable evolution, albeit slower. In purely stellar cases the pattern speed of the bar…

Astrophysics · Physics 2009-11-07 E. Athanassoula

Properties of bars and bulges in the Hubble sequence are discussed, based on the analysis of 216 disk galaxies (S0s and spirals from NIRS0S and OSUBGS surveys, respectively). For that purpose we have collected together, and completed when…

Astrophysics · Physics 2009-11-13 E. Laurikainen , H. Salo , R. Buta , J. H. Knapen

Recent large scale surveys of galactic bulge stars allowed to build a detailed map of the bulge kinematics. The bulge exhibits cylindrical rotation consistent with a disky origin which evolved through bar driven secular evolution. However…

Astrophysics of Galaxies · Physics 2016-07-06 Carine Babusiaux