Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Weighing Andromeda: Mass estimates of the M~31 galaxy

Souradeep Bhattacharya

TL;DR

This study surveys eight decades of Andromeda (M31) mass measurements, spanning rotation-curve analyses, tracer dynamics (satellites, globular clusters, PNe), substructure kinematics, Local Group dynamics, and cosmological-simulation analogues. It documents a clear progression from inner-disc enclosed masses to large-halo constraints, highlighting substantial method-dependent variation and sensitivity to priors such as distance and halo profile. The authors converge on a present total mass near $1.56\times10^{12} M_{\odot}$, with most techniques yielding values in the $1-2\times10^{12} M_{\odot}$ range, but emphasize significant systematic uncertainties. The work underscores the importance of combining diverse tracers and simulations to robustly anchor M31's mass, with implications for Local Group dynamics and galaxy formation in a cosmological context. Key insights include the relevance of giant-stream kinematics, LG timing arguments, and halo-property priors in shaping the inferred mass scale.

Abstract

Andromeda (M 31) is the nearest giant spiral galaxy to our Milky Way, and over the past few decades, has been dubbed the most massive member of the Local Group. I explore the evolution of the measured mass of M 31 over the past ~80 years, reviewing the different observational and modelling techniques that have developed over time to measure its mass. I discuss the best present-day constraints of the mass of M 31 and the consistency of different techniques.

Weighing Andromeda: Mass estimates of the M~31 galaxy

TL;DR

This study surveys eight decades of Andromeda (M31) mass measurements, spanning rotation-curve analyses, tracer dynamics (satellites, globular clusters, PNe), substructure kinematics, Local Group dynamics, and cosmological-simulation analogues. It documents a clear progression from inner-disc enclosed masses to large-halo constraints, highlighting substantial method-dependent variation and sensitivity to priors such as distance and halo profile. The authors converge on a present total mass near , with most techniques yielding values in the range, but emphasize significant systematic uncertainties. The work underscores the importance of combining diverse tracers and simulations to robustly anchor M31's mass, with implications for Local Group dynamics and galaxy formation in a cosmological context. Key insights include the relevance of giant-stream kinematics, LG timing arguments, and halo-property priors in shaping the inferred mass scale.

Abstract

Andromeda (M 31) is the nearest giant spiral galaxy to our Milky Way, and over the past few decades, has been dubbed the most massive member of the Local Group. I explore the evolution of the measured mass of M 31 over the past ~80 years, reviewing the different observational and modelling techniques that have developed over time to measure its mass. I discuss the best present-day constraints of the mass of M 31 and the consistency of different techniques.
Paper Structure (11 sections, 1 figure, 1 table)

This paper contains 11 sections, 1 figure, 1 table.

Table of Contents

  1. Introduction
  2. Mass measurements of the Andromeda galaxy
  3. The disc rotation curve and early mass measurements of M 31
  4. Satellite radial velocity measurements
  5. Globular cluster radial velocity measurements
  6. Mass models of M 31
  7. Substructure radial velocity measurements
  8. Local Group kinematics
  9. Cosmological simulations
  10. Other techniques
  11. Discussion

Figures (1)

  • Figure 1: The measured mass of M 31 (in log scale) as a function of publication year. Different symbols refer to different mass measurement techniques that are described in Section \ref{['sect:mass']}. Star: RC -- HII regions; Narrow plus: RC -- HI gas; Diamond: Satellites; Circle -- GCs ; Square -- LG kinematics; Pentagon -- Mass models; Cross -- Substructures; Broad plus -- simulations; Triangles -- others.