Deep wide field HI imaging of Messier 31

TL;DR

This paper presents a deep 21-cm HI survey of Messier 31, revealing new structures and analyzing its dynamics, mass distribution, and possible tidal interaction effects.

Contribution

It provides the first detailed HI distribution and kinematic analysis of M31 with new structural discoveries and dynamical mass estimates.

Findings

Discovered thin HI spur-like structures and an external arm.

Estimated the dynamical mass within 38 kpc as 4.7 ± 0.5 x10^11 Msol.

Identified HI perturbations likely caused by tidal interactions.

Abstract

We report on preliminary results from a new deep 21-cm survey of the Andromeda galaxy, based on observations performed with the Synthesis Telescope and the 26-m antenna at DRAO. The HI distribution and kinematics of the disc are analyzed and basic dynamical properties are derived. New HI structures are discovered, like thin HI spur-like structures and an external arm in the disc outskirts. The HI spurs are related to perturbed stellar clumps outside the main disc of M31. The external arm lies on the far, receding side of the galaxy and has no obvious counterpart in the opposite side. These HI perturbations probably result from tidal interactions with companions. It is found a dynamical mass of 4.7 +/- 0.5 x10^11 Msol enclosed within a radius R = 38 kpc and a total mass of ~1 x10^12 Msol inside the virial radius.