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We measure the anisotropy of dark matter flows on small scales in the near environment of haloes using a large set of simulations. We rely on two different approaches to quantify the anisotropy of the cosmic infall: we measure the flows at…

Astrophysics · Physics 2009-11-10 Dominique Aubert , Christophe Pichon , Stephane Colombi

We study the population of satellite galaxies formed in a suite of N-body/gasdynamical simulations of galaxy formation in a LCDM universe. We find little spatial or kinematic bias between the dark matter and the satellite population. The…

Astrophysics · Physics 2009-06-23 L. V. Sales , J. F. Navarro , M. G. Abadi , M. Steinmetz

We report the first determination of the distance to the Galactic centre based on the kinematics of halo objects. We apply the statistical-parallax technique to the sample of ~2500 Blue Horizontal Branch (BHB) stars compiled by Xue et al.…

Astrophysics of Galaxies · Physics 2020-09-17 N. D. Utkin , A. K. Dambis

The initial orbits of infalling subhalos largely determine the subsequent evolution of the subhalos and satellite galaxies therein and shed light on the assembly of their hosts. Using a large set of cosmological simulations of various…

Cosmology and Nongalactic Astrophysics · Physics 2021-01-06 Zhao-Zhou Li , Dong-Hai Zhao , Y. P. Jing , Jiaxin Han , Fu-Yu Dong

Using a sample of 248 metal-poor stars (RR Lyraes, red giants and RHB stars) which is remarkable for the accuracy of its 6-D kinematical data, we find a new component for the local halo which has an axial ratio c/a ~ 0.2, a similar…

We determine magnesium isotopic abundances of metal poor dwarf stars from the galactic halo, to shed light on the onset of asymptotic giant branch (AGB) star nucleossynthesis in the galactic halo and constrain the timescale of its…

Solar and Stellar Astrophysics · Physics 2018-04-18 Marilia Carlos , Amanda I. Karakas , Judith G. Cohen , Chiaki Kobayashi , Jorge Melendez

The halo stars on highly radial orbits should inevitably pass the center regions of the Milky Way. Under the assumption that the stellar halo is in dynamical equilibrium and axisymmetric, we integrate the orbits of $\sim 10,000$ halo…

Astrophysics of Galaxies · Physics 2022-11-16 Chengqun Yang , Ling Zhu , Behzad Tahmasebzadeh , Xiang-Xiang Xue , Chao Liu

We carry out a maximum-likelihood kinematic analysis of a sample of 1170 blue horizontal branch (BHB) stars from the Sloan Digital Sky Survey presented in Sirko et al. (2003) (Paper I). Monte Carlo simulations and resampling show that the…

Dark matter haloes from cosmological N-body simulations typically have triaxial shapes and anisotropic velocity distributions. Recently it has been shown that the velocity anisotropy, beta, of cosmological haloes and major merger remnants…

Cosmology and Nongalactic Astrophysics · Physics 2012-11-13 Martin Sparre , Steen H. Hansen

(Abridged) We perform an analysis of spectra and photometry for 22,770 stars included in the third data release (DR3) of the SDSS. We measure radial velocities and, based on a model-atmosphere analysis, derive estimates ofthe atmospheric…

Astrophysics · Physics 2009-09-29 C. Allende Prieto , T. C. Beers , R. Wilhelm , H. J. Newberg , C. M. Rockosi , B. Yanny , Y. S. Lee

Using a large sample of bright nearby stars with accurate Gaia Data Release 2 astrometry and auxiliary spectroscopy we map out the properties of the principle Galactic components such as the "thin" and "thick" discs and the halo. We show…

We investigate the stellar kinematics of a sample of galaxies extracted from the hydrodynamic cosmological Magneticum Pathfinder simulations out to $5$ half-mass radii. We construct differential radial stellar spin profiles quantified by…

Astrophysics of Galaxies · Physics 2020-03-04 Felix Schulze , Rhea-Silvia Remus , Klaus Dolag , Sabine Bellstedt , Andreas Burkert , Duncan A. Forbes

We use the distribution of accreted stars in SDSS-Gaia DR2 to demonstrate that a non-trivial fraction of the dark matter halo within Galactocentric radii of 7.5-10 kpc and $|z| > 2.5$ kpc is in substructure, and thus may not be in…

Astrophysics of Galaxies · Physics 2019-07-31 Lina Necib , Mariangela Lisanti , Vasily Belokurov

Correlations between stellar kinematics and chemical abundances are fossil evidence for evolutionary connections between Galactic structural components. Extensive stellar surveys show that the only tolerably clear distinction between…

Astrophysics · Physics 2009-10-22 Gerard Gilmore

Both simulations and observations have confirmed that the spin of haloes/galaxies is correlated with the large scale structure (LSS) with a mass dependence such that the spin of low-mass haloes/galaxies tend to be parallel with the LSS,…

Cosmology and Nongalactic Astrophysics · Physics 2017-11-08 Peng Wang , Xi Kang

A possible relation between the high dispersion in metallicity of metal-poor halo stars and the minor merger processes in the history of the Galaxy is presented. The foreign populations of stars in the satellites through minor merger…

Astrophysics · Physics 2007-05-23 Y. Lu , K. S. Cheng , L. C. Deng

We use distant Blue Horizontal Branch stars with Galactocentric distances 16 < r/kpc < 48 as kinematic tracers of the Milky Way dark halo. We model the tracer density as an oblate, power-law embedded within a spherical power-law potential.…

Astrophysics of Galaxies · Physics 2015-06-04 A. J. Deason , V. Belokurov , N. W. Evans , J. H. An

Studies of the kinematics of gaseous halos in some spiral galaxies have shown that the rotational velocity of the gas decreases with height above the midplane (z). This vertical velocity gradient has been observed in both the neutral and…

Astrophysics · Physics 2007-05-23 G. H. Heald , R. J. Rand , R. A. Benjamin , J. A. Collins , J. Bland-Hawthorn

Based on the first Gaia data release and spectroscopy from the LAMOST Data Release 4, we study the kinematics and chemistry of the local halo stars. The halo stars are identified kinematically with a relative speed of at least 220 km…

Astrophysics of Galaxies · Physics 2018-08-22 Cuihua Du , Hefan Li , Shuai Liu , Thomas Donlon , Heidi Jo Newberg

We analyse systems analogous to the Milky Way (MW) in the EAGLE cosmological hydrodynamics simulation in order to deduce the likely structure of the MW's dark matter halo. We identify MW-mass haloes in the simulation whose satellite…

Astrophysics of Galaxies · Physics 2021-01-06 Shi Shao , Marius Cautun , Alis J. Deason , Carlos S. Frenk