Dark matter fraction derived from the M31 rotation curve

Abstract

Mass estimates of a spiral galaxy derived from its rotation curve must account for the galaxy's past accretion history. There are several lines of evidence indicating that M31 experienced a major merger 2 to 3 Gyr ago. Here, we have generated a dynamical model of M31 as a merger remnant that reproduces most of its properties, from the central bar to the outskirts. The model accounts for the past major merger, and reproduces the details of M31's rotation curve, including its 14 kpc bump and the observed increase of velocity beyond 25 kpc. Furthermore, we find non-equilibrium and oscillatory motions in the gas of the merger-remnant outskirts caused by material in a tidal tail returning to the merger remnant. A total dynamical M31 mass of 4.5 $\times 10^{11}{M}_{\odot }$ within 137 kpc has been obtained after scaling it to the observed HI rotation curve. Within this radial distance, 68% of the total dynamical mass is dark.

A&A, 9 pages, 10 Figures, see also a video showing the formation of the M31 gas disk and of its rotation curve at https://www.youtube.com/watch?v=_W8tdlUbv2k

References in corpus (9)

• The Panchromatic Hubble Andromeda Treasury XI: The Spatially-Resolved Recent Star Formation History of M31
• Dark Halos of M31 and the Milky Way
• Detection of the Keplerian decline in the Milky Way rotation curve
• A clear age-velocity dispersion correlation in Andromeda's stellar disk
• The Need for Speed: Escape velocity and dynamical mass measurements of the Andromeda galaxy
• DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of our Nearest Neighbor
• Which Milky Way masses are consistent with the slightly declining 5-25 kpc rotation curve?
• The survey of planetary nebulae in Andromeda (M31) VI. Kinematics of M31 inner-halo substructures and comparison with major-merger simulation predictions
• The Escape Velocity Profile of the Milky Way from Gaia DR3

Cited by in corpus (3)

• An intriguing coincidence between the majority of vast polar structure dwarfs and a recent major merger at the M31 position
• The Panchromatic Hubble Andromeda Southern Treasury (PHAST). II. The Spatially Resolved Recent Star Formation History in M31
• Impact of merger histories on the timing argument estimate of the Local Group mass