A radial velocity survey of low Galactic latitude structures – III. The Monoceros Ring in front of the Carina and Andromeda galaxies

As part of our radial velocity survey of low Galactic latitude structures that surround the Galactic disc, we report the detection of the so-called Monoceros Ring in the foreground of the Carina dwarf galaxy at Galactic coordinates (l, b) = (260°, −22°) based on Very Large Telescope/Fibre Large Array Multi Element Spectrograph observations of the dwarf galaxy. At this location, 20° in longitude greater than previous detections, the Ring has a mean radial velocity of 145 ± 5 km s−1 and a velocity dispersion of only 17 ± 5 km s−1. Based on Keck/Deep Imaging Multi-Object Spectrograph observations, we also determine that the Ring has a mean radial velocity of −75 ± 4 km s−1 in the foreground of the Andromeda galaxy at (l, b) ∼ (122°, −22°), along with a velocity dispersion of 26 ± 3 km s−1. These two kinematic detections are both highly compatible with known characteristics of the structure and, along with previous detections, provide radial velocity values of the Ring over the 120° < l < 260° range. This should place strong constraints on numerical models of the accretion of the dwarf galaxy that is believed to be the progenitor of the Ring.