Mapping the Galactic Halo with blue horizontal branch stars from the 2dF quasar redshift survey

Abstract

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 obeys a single power-law density profile of index ~-2.5 in two different directions separated by 150 degrees on the sky. This suggests that the halo is spherical. Our map shows no large kinematically coherent structures (streams, clouds or plumes) and appears homogeneous. However, we find that at least 20% of the stars in the halo reside in substructures and that these substructures are dynamically young. The velocity dispersion profile of the halo appears to increase towards large radii while the stellar velocity distribution is non Gaussian beyond 60 kpc. We argue that the outer halo consists of a multitude of low luminosity overlapping tidal streams from recently accreted objects.

Accepted for publication in the Astrophysical Journal Requires emulateapj to process

References in corpus (9)

• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• Two Stellar Components in the Halo of the Milky Way
• The accretion origin of the Milky Way's stellar halo
• The Haunted Halos of Andromeda and Triangulum: A panorama of galaxy formation in action
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• The Metal-Poor Halo of the Andromeda Spiral Galaxy (M31)
• A kinematically selected, metal-poor stellar halo in the outskirts of M31
• Modeling The Structure And Dynamics of Dwarf Spheroidal Galaxies with Dark Matter And Tides
• Kinematic Structure in the Galactic Halo at the North Galactic Pole: RR Lyrae and BHB Stars show different kinematics

Cited by in corpus (22)

• The Milky Way stellar halo out to 40 kpc : Squashed, broken but smooth
• The Luminosity Profile and Structural Parameters of the Andromeda Galaxy
• Kinematics of the stellar halo and the mass distribution of the Milky Way using BHB stars
• The Case for the Dual Halo of the Milky Way
• Quantifying Kinematic Substructure in the Milky Way's Stellar Halo
• Galactic Stellar Populations in the Era of SDSS and Other Large Surveys
• Stellar labels for hot stars from low-resolution spectra - I. the HotPayne method and results for 330,000 stars from LAMOST DR6
• The first all-sky view of the Milky Way stellar halo with Gaia+2MASS RR Lyrae
• Action-space clustering of tidal streams to infer the Galactic potential
• The Profile of the Galactic Halo from Pan-STARRS1 3$\pi$ RR Lyrae
• The Galactic Thick Disc density profile traced with RR Lyrae stars
• A-type stars in the Canada-France Imaging Survey I. The stellar halo of the Milky Way traced to large radius by blue horizontal branch stars
• Discovery of distant RR Lyrae stars in the Milky Way using DECam
• Creating mock catalogues of stellar haloes from cosmological simulations
• Characterizing stellar halo populations II: The age gradient in blue horizontal-branch stars
• A comprehensive view of the Virgo Stellar Stream
• The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility
• The Stellar Density Profile of the Distant Galactic Halo
• A new calibration for the Blue Horizontal Branch
• Mapping the Milky Way's stellar halo with 2D data
• The BHB stars in the Survey Fields of Rodgers et al. (1993): New Observations and Comparisons with other Recent Surveys
• Tomography of stellar halos: what does anisotropy in a stellar halo tell us?