The AAT/WFI survey of the Monoceros Ring and Canis Major Dwarf galaxy: II. from l = (280 - 025)deg

TL;DR

This survey maps the Monoceros Ring and Canis Major dwarf galaxy around the Galactic Plane, finding new detections and analyzing their distribution to understand their structure and relation to the Milky Way's evolution.

Contribution

It provides new observational evidence of the Monoceros Ring's extent and asymmetry, and assesses the influence of Galactic Warp on these structures.

Findings

Two new Monoceros Ring detections at specific longitudes.

More detections are found in the northern Galactic hemisphere.

The Galactic Warp does not significantly alter the CMD shape in surveyed fields.

Abstract

This paper concludes a systematic search for evidence of the Monoceros Ring and Canis Major dwarf galaxy around the Galactic Plane. Presented here are the results for the Galactic longitude range of l = (280 - 025)deg. Testing the claim that the Monoceros Ring encircles the entire Galaxy, this survey attempts to document the position of the Monoceros Ring with increasing Galactic longitude. Additionally, with the discovery of the purported Canis Major dwarf galaxy, searching for more evidence of its interaction is imperative to tracing its path through the Galaxy and understanding its role in the evolution of the Milky Way. Two new detections of the Monoceros Ring have been found at (l, b) = (280,+15)deg and (300,+10)deg. Interestingly, in general there seem to be more detections above the Plane than below it; in this survey around 2/3 of the firm Monoceros Ring detections are in the North. This coincides with the Northern detections appearing to be qualitatively denser and broader than their Southern counterparts. The maximum of the Galactic Warp in the South is also probed in this survey. It is found that these fields do not resemble those in the Canis Major region suggesting that the Warp does not change the shape of the CMD as is witnessed around Canis Major. The origins and morphology of the Monoceros Ring is still elusive primarily due to its enormous extent on the sky. Continued probing of the Galactic Outer Disc is needed before a consensus can be reached on its nature.