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The debris from past merger events is expected and, to some extent, known to populate the stellar halo near the Sun. We aim to identify and characterise such merger debris using Gaia DR3 data supplemented by metallicity and chemical…

We analyze the observed spatial, chemical and dynamical distributions of local metal-poor stars, based on photometrically derived metallicity and distance estimates along with proper motions from the Gaia mission. Along the Galactic prime…

Astrophysics of Galaxies · Physics 2021-09-29 Deokkeun An , Timothy C. Beers

We have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high latitude sky survey. Our sample contains 101 photometrically selected and spectroscopically…

Based on Sloan Digital Sky Survey (SDSS) photometric data, Gu developed a new Monte-Carlo-based method for estimating the stellar metallicity distribution functions (MDFs). This method enables a more reliable determination of MDFs compared…

Astrophysics of Galaxies · Physics 2019-06-05 Jiayin Gu , Cuihua Du , Wenbo Zuo

Galaxies can be classified in two broad sequences which are likely to reflect their formation mechanism. The `main sequence', consisting of spirals, irregulars and all dwarf galaxies, is probably produced by gas settling within dark matter…

Astrophysics · Physics 2009-10-30 S. Mao , H. J. Mo

Modern Galactic surveys have revealed an ancient merger that dominates the stellar halo of our Galaxy (\textit{Gaia}-Sausage-Enceladus, GSE). Using chemical abundances and kinematics from the H3 Survey, we identify 5559 halo stars from this…

The hierarchical structure formation model predicts that stellar halos should form, at least partly, via mergers. If this was a predominant formation channel for the Milky Way's halo, imprints of this merger history in the form of moving…

Astrophysics of Galaxies · Physics 2017-02-01 Amina Helmi , Jovan Veljanoski , Maarten A. Breddels , Hao Tian , Laura V. Sales

We aim to quantify the chemical and kinematical properties of the Galactic disks with a sample of 119,558 giant stars having abundances and 3D velocities taken or derived from the APOGEE DR17 and Gaia EDR3 catalogs. The Gaussian Mixture…

Astrophysics of Galaxies · Physics 2022-04-20 Guozhen Hu , Zhengyi Shao

We explore the hypothesis that the classical and ultra-faint dwarf spheroidal satellites of the Milky Way have been the building blocks of the Galactic halo by comparing their [O/Fe] and [Ba/Fe] versus [Fe/H] patterns with the ones observed…

Astrophysics of Galaxies · Physics 2017-05-19 E. Spitoni , F. Vincenzo , F. Matteucci , D. Romano

We model the formation of the Galactic stellar halo via the accretion of satellite galaxies onto a time-dependent semi-cosmological galactic potential. Our goal is to characterize the substructure left by these accretion events in a close…

Astrophysics of Galaxies · Physics 2015-05-18 Facundo A. Gómez , Amina Helmi , Anthony G. A. Brown , Yang-Shyang Li

We present a detailed study of the chemical diversity of the metal-poor Milky Way (MW) using data from the GALAH DR3 survey. Considering 17 chemical abundances relative to iron ([X/Fe]) for 9,923 stars, we employ Principal Component…

Astrophysics of Galaxies · Physics 2024-07-29 Nicole Buckley , Payel Das , Paula Jofré , Robert M. Yates , Keith Hawkins

Based on a large spectroscopic sample of $\sim$ 4,300 RR Lyrae stars with metallicity, systemic radial velocity and distance measurements, we present a detailed analysis of the chemical and kinematic properties of the Galactic halo. Using…

Astrophysics of Galaxies · Physics 2022-09-28 Gaochao Liu , Yang Huang , Sarah Ann Bird , Huawei Zhang , Fei Wang , Haijun Tian

The Galactic halo preserves a record of the Milky Way's earliest assembly and contains both in-situ stars and stars accreted from dwarf galaxies. Possible planets around these stars, therefore, probe formation in ancient, metal-poor…

Earth and Planetary Astrophysics · Physics 2026-05-20 Dolev Bashi , Michelle Kunimoto , Kevin K. Hardegree-Ullman , Tianjun Gan , Sharon X. Wang , Zhen Yuan

Using the astrometry from the ESA's Gaia mission, previous works have shown that the Milky Way stellar halo is dominated by metal-rich stars on highly eccentric orbits. To shed light on the nature of this prominent halo component, we have…

It is well-established that the vast majority of metal-poor Galactic halo stars shows evidence for enrichment by solely massive stars. Recent observations have identified more varied behavior in the pattern of elemental abundances measured…

Astrophysics · Physics 2016-08-30 Gerard Gilmore , Rosemary F. G. Wyse

We use 666 blue horizontal branch (BHB) stars from the 2Qz redshift survey to map the Galactic halo in four dimensions (position, distance and velocity). We find that the halo extends to at least 100 kpc in Galactocentric distance, and…

Astrophysics of Galaxies · Physics 2015-05-19 Roberto De Propris , Craig D. Harrison , Peter J. Mares , CTIO , Cornell University

The stellar mass in the halo of the Milky Way is notoriously difficult to determine, owing to the paucity of its stars in the solar neighbourhood. With tentative evidence from $\it{Gaia}$ that the nearby stellar halo is dominated by a…

Astrophysics of Galaxies · Physics 2020-01-29 J. Ted Mackereth , Jo Bovy

We analyze the global structure of the Milky Way (MW)'s stellar halo including its dominant subcomponent, Gaia-Sausage-Enceladus (GSE). The method to reconstruct the global distribution of this old stellar component is to employ the…

Astrophysics of Galaxies · Physics 2022-03-14 Genta Sato , Masashi Chiba

We report the results of a systematic photometric survey of the peripheral regions of a sample of fourteen globular clusters in the outer halo of the Milky Way at distances d_GC>25 kpc from the Galactic centre. The survey is aimed at…

Recent work indicates that the nearby Galactic halo is dominated by the debris from a major accretion event. We confirm that result from an analysis of APOGEE-DR14 element abundances and $\textit{Gaia}$-DR2 kinematics of halo stars. We show…