Local Group timing argument and virial theorem mass estimators from cosmological simulations

Abstract

We identify Local Group (LG) analogs in the IllustrisTNG cosmological simulation, and use these to study two mass estimators for the LG: one based on the timing argument (TA) and one based on the virial theorem (VT). Including updated measurements of the Milky Way-M31 tangential velocity and the cosmological constant, we show that the TA mass estimator slightly overestimates the true median LG-mass, though the ratio of the TA to the true mass is consistent at the approximate 90\% c.l. These are in broad agreement with previous results using dark matter-only simulations. We show that the VT estimator better estimates the true LG-mass, though there is a larger scatter in the virial mass to true mass ratio relative to the corresponding ratio for the TA. We attribute the broader scatter in the VT estimator to several factors, including the predominantly radial orbits for LG satellite galaxies, which differs from the VT assumption of isotropic orbits. With the systematic uncertainties we derive, the updated measurements of the LG mass at 90\% c.l. are $4.75_{-2.41}^{+2.22}\times 10^{12}$ M${}_{\odot }$ from the TA and $2.0_{-1.5}^{+2.1}\times 10^{12}$ M${}_{\odot }$ from the VT. We consider the LMC's effect on the TA and VT LG mass estimates, and do not find exact LMC-MW-M31 analogues in the Illustris simulations. However, in LG simulations with satellite companions as massive as the LMC we find that the effect on the TA and VT estimators is small, though we need further studies on a larger sample of LMC-MW-M31 systems to confirm these results.

12 pages, 6 figures, Accepted for publication in MNRAS

References in corpus (12)

• Properties of galaxies reproduced by a hydrodynamic simulation
• The M31 Velocity Vector. II. Radial Orbit Towards the Milky Way and Implied Local Group Mass
• The Hubble flow around the Local Group
• M31 Transverse Velocity and Local Group Mass from Satellite Kinematics
• A dynamical model of the local cosmic expansion
• Detection of the Milky Way reflex motion due to the Large Magellanic Cloud infall
• Balancing mass and momentum in the Local Group
• Constraining the mass of the Local Group
• Solo dwarfs III: Exploring the orbital origins of isolated Local Group galaxies with Gaia Data Release 2
• Local Group Analogs in $\Lambda$CDM cosmological simulations
• The Local Group as a test system for Modified Newtonian Dynamics
• Mapping Gaia parallax systematic errors over the sky with faint Milky Way stars

Cited by in corpus (14)

• The Local Group Mass in the light of Gaia
• Implications of the Milky Way travel velocity for dynamical mass estimates of the Local Group
• Constraining Dark Energy from Local Group dynamics
• The Local Group's mass: probably no more than the sum of its parts
• Weighing Milky Way and Andromeda in an expanding $\Lambda$CDM Universe: Decreasing the Local Group mass
• Tracking the Local Group Dynamics by Extended Gravity
• The undiscovered ultra-diffuse galaxies of the Local Group
• Dark Energy as a Critical Period in Binary Motion: Bounds from Multi-scale Binaries
• Exploring the centre of mass properties of LG-like galaxies
• Galaxy groups in the presence of Cosmological Constant: Increasing the Masses of Groups
• Line-of-Sight Velocity Projection Impact on the Local Group Mass
• Timing Mass of the Local Group
• The Milky Way and M31 Orbital History: Did the Local Group evolve in isolation?
• Impact of merger histories on the timing argument estimate of the Local Group mass