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Starburst galaxies are undergoing intense episodes of star formation. In these galaxies, gas is ejected into the surrounding environment through winds created by the effect of hot stars and supernova explosions. When interacting with the…

Astrophysics of Galaxies · Physics 2024-03-12 C. A. Galante , J. Saponara , G. E. Romero , P. Benaglia

A sample of roughly 1,800 halo subdwarf stars with radial velocities and proper motions is assembled, using the repeated multi-band Sloan Digital Sky Survey photometric measurements in Stripe 82. Our sample of halo subdwarfs is extracted…

Astrophysics of Galaxies · Physics 2011-02-11 M. C. Smith , N. W. Evans , J. An

We use a combination of spatial distribution and radial velocity to search for halo sub-structures in a sample of 412 RR Lyrae stars (RRLS) that covers a $\sim 525$ square degrees region of the Virgo Overdensity (VOD) and spans distances…

Astrophysics of Galaxies · Physics 2016-11-15 A. Katherina Vivas , Robert Zinn , John Farmer , Sonia Duffau , Yiding Ping

Gaia Data Release 2 revealed detailed structures of nearby stars in phase space. These include the Hercules stream, whose origin is still debated. Most of the previous numerical studies conjectured that the observed structures originate…

Astrophysics of Galaxies · Physics 2020-09-30 Tetsuro Asano , Michiko S. Fujii , Junichi Baba , Jeroen Bédorf , Elena Sellentin , Simon Portegies Zwart

Stellar haloes form through the disruption of satellite galaxies over time, making them a promising observable for constraining galaxy merger histories. We use a dynamical decomposition technique to isolate the stellar haloes of Milky…

Astrophysics of Galaxies · Physics 2025-09-03 Katy L. Proctor , Aaron D. Ludlow , Claudia del P. Lagos , Aaron S. G. Robotham

Currently only a small number of Milky Way (MW) stars are known to exist beyond 100 kpc from the Galactic center. Though the distribution of these stars in the outer halo is believed to be sparse, they can provide evidence of more recent…

Astrophysics of Galaxies · Physics 2017-08-02 Robyn E. Sanderson , Amy Secunda , Kathryn V. Johnston , John J. Bochanski

Recent maps of the halo using RR Lyrae from Pan-STARRS1 have clearly depicted the spatial structure of the Sagittarius stream. These maps show the leading and trailing stream apocenters differ in galactocentric radius by a factor of two,…

The Milky Way halo has been built-up over cosmic time through the accretion and dissolution of star clusters and dwarf galaxies as well as through their complex interactions with the Galactic disc. Traces of these accreted structures…

Astrophysics of Galaxies · Physics 2026-01-14 Kris Youakim , Karin Lind

We analyse the phase-space structure of simulated thick discs that are the result of a significant merger between a disc galaxy and a satellite. Our main goal is to establish what would be the characteristic imprints of a merger origin for…

Astrophysics of Galaxies · Physics 2015-05-13 Álvaro Villalobos , Amina Helmi

Bars in disk galaxies slow down as they transfer their angular momentum to their dark matter halo via dynamical friction from near-resonant orbits. This bar-halo dynamical friction can become ineffective once phase mixing erases the…

Astrophysics of Galaxies · Physics 2026-03-16 Rumi Kodama , Rimpei Chiba , Tetsuro Asano , Junichi Baba , Michiko Fujii

We use the results from a constrained, cosmological MHD simulation of the Local Universe to predict the radio halo and the gamma-ray flux from the Coma cluster and compare it to current observations. The simulated magnetic field within the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 J. Donnert , K. Dolag , G. Brunetti , R. Cassano , A. Bonafede

Decoding the key dynamical processes that shape the Galactic disk structure is crucial for reconstructing the Milky Way's evolution history. The second Gaia data release unveils a novel wave pattern in the $L_Z-\langle V_R\rangle$ space,…

Astrophysics of Galaxies · Physics 2024-11-19 Chengye Cao , Zhao-Yu Li , Ralph Schönrich , Teresa Antoja

The nearest giant spiral, M31, exhibits a kinematically hot stellar disc, a global star formation episode ~2-4 Gyr ago, and conspicuous substructures in its stellar halo that are suggestive of a recent accretion event. Recent chemodynamical…

Astrophysics of Galaxies · Physics 2025-07-02 C. Tsakonas , M. Arnaboldi , S. Bhattacharya , F. Hammer , Y. Yang , O. Gerhard , R. F. G. Wyse , D. Hatzidimitriou

To unravel the formation history of the Milky Way, we estimate the accretion times of six phase-space substructures in the stellar halo, using the orbital frequencies toward two spatial directions ($r, \phi$) in spherical coordinates. These…

Astrophysics of Galaxies · Physics 2026-01-22 Hefan Li , Masashi Chiba , Xiang-Xiang Xue , Gang Zhao

We investigate shock structures driven by merger events in high-resolution simulations that result in a galaxy with a virial mass M ~ 1e12 Msol. We find that the sizes and morphologies of the internal shocks resemble remarkably well those…

Astrophysics of Galaxies · Physics 2023-03-15 Klaus Dolag , Ludwig M. Böss , Bärbel S. Koribalski , Ulrich P. Steinwandel , Milena Valentini

Recently, an increasing number of wide binaries has been discovered. Their chemical and dynamical properties are studied through extensive surveys and pointed observations. However, the formation of these wide binaries is far from clear,…

We identify ten -- seven for the first time -- elements of cold halo substructure (ECHOS) in the volume within 17.5 kpc of the Sun in the inner halo of the Milky Way. Our result is based on the observed spatial and radial velocity…

We determine the Milky Way (MW) mass profile inferred from fitting physically motivated models to the Gaia DR2 Galactic rotation curve and other data. Using various hydrodynamical simulations of MW-mass haloes, we show that the presence of…

To account for the observed differential metallicity distribution (DMD) of the Milky Way halo, a semi-analytical model is presented in the framework of the hierarchical merging paradigm for structure formation. It is assumed that the Milky…

Astrophysics · Physics 2009-11-13 Nikos Prantzos

Reconstructing the mass assembly history of the Milky Way relies on obtaining detailed measurements of the properties of many stars in the Galaxy, especially in the stellar halo. One of the most constraining quantities is stellar age, as it…

Astrophysics of Galaxies · Physics 2024-06-11 Danny Horta , Yuxi , Lu , Melissa K. Ness , Mariangela Lisanti , Adrian M. Price-Whelan