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Thanks to modern sky surveys, over twenty stellar streams and overdensity structures have been discovered in the halo of the Milky Way. In this paper, we present an analysis of spectroscopic observations of individual stars from one such…

Using kinematic data from the Gaia Data Release 3 catalog, along with metallicity estimates robustly derived from Gaia XP spectra, we have explored the Galactic stellar halo in search of both known and potentially new substructures. By…

Astrophysics of Galaxies · Physics 2024-10-10 Haoyang Liu , Cuihua Du , Dashuang Ye , Jian Zhang , Mingji Deng

We report spectroscopic observations with the Gemini South Telescope of 5 faint V~20 RR Lyrae stars associated with the Pisces overdensity. At a heliocentric and galactocentric distance of ~80 kpc, this is the most distant substructure in…

Astrophysics of Galaxies · Physics 2015-05-18 Branimir Sesar , A. Katherina Vivas , Sonia Duffau , Zeljko Ivezic

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 use K-giant stars selected from the LAMOST DR5 to study the variation of the rotational velocity of the galactic halo at different space positions. Modelling the rotational velocity distribution with both the halo and disk components, we…

Astrophysics of Galaxies · Physics 2020-08-26 Hao Tian , Chao Liu , Yougang Wang , Yan Xu , Chengqun Yang , Bo Zhang , Xiang-Xiang Xue

We present and analyze the positions, distances, and radial velocities for over 4000 blue horizontal-branch (BHB) stars in the Milky Way's halo, drawn from SDSS DR8. We search for position-velocity substructure in these data, a signature of…

We describe first results of a spectroscopic probe of selected fields from the Grid Giant Star Survey. Multifiber spectroscopy of several hundred stars in a strip of eleven fields along delta approximately -17^{circ}, in the range 12 <~…

We present an improved analysis of halo substructure traced by RR Lyrae stars in the SDSS stripe 82 region. With the addition of SDSS-II data, a revised selection method based on new ugriz light curve templates results in a sample of 483 RR…

We identify a halo substructure in the Tycho Gaia Astrometric Solution (TGAS) dataset, cross-matched with the RAVE-on data release. After quality cuts, the stars with large radial action ($J_R > 800$ kms$^{-1}$ kpc) are extracted. A subset…

Astrophysics of Galaxies · Physics 2018-01-25 G. C. Myeong , N. W. Evans , V. Belokurov , S. Koposov , J. L. Sanders

Based on the second Gaia data release (Gaia DR2) and spectroscopy from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data, we identified 20,089 halo stars kinematically and chemically. The halo streams in the solar…

Astrophysics of Galaxies · Physics 2019-04-03 Hefan Li , Cuihua Du , Shuai Liu , Thomas Donlon , Heidi Jo Newberg

Based on 4,\,098 very metal-poor (VMP) stars with 6D phase-space and chemical information from \textit{Gaia} DR3 and LAMOST DR9 as tracers, we apply an unsupervised machine learning algorithm, Shared Nearest Neighbor (SNN), to identify…

Astrophysics of Galaxies · Physics 2023-12-14 Dashuang Ye , Cuihua Du , Jianrong Shi , Jun Ma

A density based hierarchical group-finding algorithm is used to identify stellar halo structures in a catalog of M-giants from the Two Micron All Sky Survey (2MASS). The intrinsic brightness of M-giant stars means that this catalog probes…

We use the second Gaia data release (Gaia DR2), combined with RAVE spectroscopic surveys, to identify the substructures in the nearby stellar halo. We select 3,845 halo stars kinematically and chemically, and determine their density…

Astrophysics of Galaxies · Physics 2020-10-28 Hefan Li , Cuihua Du , Yanbin Yang , Heidi Jo Newberg , Jun Ma , Jianrong Shi , Yunsong Piao

We explore the phase-space structure of nearby halo stars identified kinematically from Gaia DR2 data. We focus on their distribution in velocity and in "integrals of motion" space as well as on their photometric properties. Our sample of…

Astrophysics of Galaxies · Physics 2018-06-27 Helmer H. Koppelman , Amina Helmi , Jovan Veljanoski

We use Canada-France-Hawaii Telescope Legacy Survey data for 170 deg^2, recalibrated and transformed to the Sloan Digital Sky Survey ugri photometric system, to study the distribution of near-turnoff main-sequence stars in the Galactic halo…

Astrophysics of Galaxies · Physics 2015-05-20 Branimir Sesar , Mario Juric , Zeljko Ivezic

A pole-count analysis of the infrared 2MASS survey is presented, in order to identify faint stream-like structures within the halo of the Milky Way. Selecting stars with colours consistent with M-giant stars, we find a strong over-density…

Astrophysics · Physics 2016-08-30 R. A. Ibata , G. F. Lewis , M. J. Irwin , L. Cambresy

We present a catalog of distances for 19544 K giants drawn from LAMOST DR8. Most of them are located in the halo of the Milky Way up to ~120~kpc. There are 15% K giants without SDSS photometry, for which we supplements with Pan-STARRS1…

Astrophysics of Galaxies · Physics 2023-05-08 Lan Zhang , Xiang-Xiang Xue , Chengqun Yang , Feilu Wang , Hans-Walter Rix , Gang Zhao , Chao Liu

We present a new method for identifying Galactic halo substructures accreted from dwarf galaxies by combining metallicity distribution functions (MDFs) with orbital parameters. Using apogalactic distance-orbital phase space, we assume that…

Astrophysics of Galaxies · Physics 2025-08-25 Young Kwang Kim , Young Sun Lee , Timothy C. Beers

We present the latitude-normalized radial velocity (vb) distribution of 3318 subsolar metallicity, V<13.5 stars from the Grid Giant Star Survey (GGSS) in Southern Hemisphere fields. The sample includes giants mostly within ~5 kpc from the…

We construct a new sample of ~1700 solar neighbourhood halo subdwarfs from the Sloan Digital Sky Survey, selected using a reduced proper motion diagram. Radial velocities come from the SDSS spectra and proper motions from the light-motion…

Astrophysics of Galaxies · Physics 2009-11-19 M. C. Smith , N. W. Evans , V. Belokurov , P. C. Hewett , D. M. Bramich , G. Gilmore , M. J. Irwin , S. Vidrih , D. B. Zucker