A deep view of the Monoceros ring in the Anticenter direction: clues of its extra-Galactic origin

TL;DR

This study uses deep imaging data to analyze the Monoceros ring in the Anticenter direction, providing evidence supporting its extra-Galactic origin by comparing observed features with Galactic models.

Contribution

The paper presents deep imaging observations that reveal the Monoceros ring's morphology and density, challenging Galactic disk flare explanations and supporting an extra-Galactic origin.

Findings

Monoceros ring detected as a narrow Main Sequence feature

Morphology and density inconsistent with Galactic disk flare models

Supports an extra-Galactic origin hypothesis

Abstract

We present the results of deep imaging obtained at the CFHT with MegaCam in the Anticenter direction at two different heights above the Galactic disk. We detect the presence of the Monoceros ring in both fields as a conspicuous and narrow Main Sequence feature which dominates star counts over a large portion of the color-magnitude diagram down to g'~24. The comparison of the morphology and density of this feature with a large variety of Galactic models excludes the possibility that it can be due to a flare of the Galactic disk, supporting an extra-Galactic origin for this ring-like structure.