Dynamical evidence for a strong tidal interaction between the Milky Way and its satellite, Leo V

Abstract

We present a chemodynamical analysis of the Leo~V dwarf galaxy, based on Keck II DEIMOS spectra of 8 member stars. We find a systemic velocity for the system of $⟨v_r⟩=170.9_{-1.9}^{+2.1}$kms${}^{-1}$, and barely resolve a velocity dispersion for the system, with ${\sigma }_{vr}=2.3_{-1.6}^{+3.2}$kms${}^{-1}$, consistent with previous studies of Leo~V. The poorly resolved dispersion means we are unable to adequately constrain the dark matter content of Leo~V. We find an average metallicity for the dwarf of [Fe/H]$=-2.48\pm 0.21$, and measure a significant spread in the iron abundance of its member stars, with $-3.1\le$[Fe/H]$\le -1.9$ dex, which cleanly identifies Leo~V as a dwarf galaxy that has been able to self-enrich its stellar population through extended star formation. Owing to the tentative photometric evidence for tidal substructure around Leo~V, we also investigate whether there is any evidence for tidal stripping or shocking of the system within its dynamics. We measure a significant velocity gradient across the system, of $\frac{\mathrm{d}v}{\mathrm{d}\chi }=-4.1_{-2.6}^{+2.8}$kms${}^{-1}$ per arcmin (or $\frac{\mathrm{d}v}{\mathrm{d}\chi }=-71.9_{-45.6}^{+50.8}$kms${}^{-1}$~kpc${}^{-1}$), which points almost directly toward the Galactic centre. We argue that Leo~V is likely a dwarf on the brink of dissolution, having just barely survived a past encounter with the centre of the Milky Way.

14 pages, 12 figures, accepted for publication in MNRAS. Updated to include minor revisions from referee process

References in corpus (17)

• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• 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
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data
• Hundreds of Milky Way Satellites? Luminosity Bias in the Satellite Luminosity Function
• The Tidal Evolution of Local Group Dwarf Spheroidals
• The kinematic status and mass content of the Sculptor dwarf spheroidal galaxy
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• Analysis and calibration of CaII triplet spectroscopy of Red Giant Branch stars from VLT/FLAMES observations
• Leo V: A Companion of a Companion of the Milky Way Galaxy
• Hydra II: a faint and compact Milky Way dwarf galaxy found in the Survey of the Magellanic Stellar History
• A dynamical model of the local cosmic expansion
• A new distant Milky Way globular cluster in the Pan-STARRS1 3π survey
• ATLAS lifts the Cup: Discovery of a New Milky Way satellite in Crater
• Systemic Proper Motions of Milky Way Satellites from Stellar Redshifts: the Carina, Fornax, Sculptor and Sextans Dwarf Spheroidals
• The Star Formation History and Extended Structure of the Hercules Milky Way Satellite
• The Infrared Ca II triplet as metallicity indicator

Cited by in corpus (6)

• Farthest Neighbor: The Distant Milky Way Satellite Eridanus II
• Revised and new proper motions for confirmed and candidate Milky Way dwarf galaxies
• A detailed study of Andromeda XIX, an extreme local analogue of ultra diffuse galaxies
• Serendipitous discovery of RR Lyrae stars in the Leo V ultra-faint galaxy
• Constraining the primordial curvature perturbation using dark matter substructure
• Chemodynamics of BoötesI with $S^5$: Revised Velocity Gradient, Dark Matter Density, and Galactic Chemical Evolution Constraints