New Insights into the Mass of the Local Group: Milky Way and Andromeda

A recent paper titled "Weighing Milky Way and Andromeda in an expanding (\Lambda)CDM Universe: Decreasing the Local Group mass" by David Benisty presents new findings regarding the mass of the Local Group of galaxies, which includes the Milky Way and Andromeda. The study utilizes a two-body problem approach within a (\Lambda) cold dark matter ((\Lambda)CDM) framework to analyze the dynamics of the Local Group (LG).

Key findings from the research indicate that the complete (\Lambda)CDM background predicts a mass for the Local Group that is approximately 10% lower than previous estimates. Conversely, using only the (\Lambda) component suggests a mass that is about 10% higher. The study highlights the importance of considering the Large Magellanic Cloud (LMC) and simulations in refining mass estimates.

The paper reports that simulations accounted for the effects of extended halos rather than treating them as point particles, leading to a predicted mass of (3.89 \pm 0.62 \times 10^{12} M_{\odot}). However, when factoring in the LMC's influence on the dynamics between the Milky Way and Andromeda, the estimated mass decreases to (2.33 \pm 0.72 \times 10^{12} M_{\odot}).

The implications of these findings are significant for understanding the mass distribution and dynamics of the Local Group, as well as the role of dark matter in these calculations. The results align with other mass estimates derived from the Hubble flow and the Virial Theorem involving dwarf galaxies, suggesting a more consistent understanding of the Local Group's mass without necessitating an additional dark matter halo around the galaxies.

This research has been accepted for publication in Astronomy & Astrophysics Letters and can be cited as arXiv:2401.09546.