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SUMMARY:The Mass of the Local Group
DTSTART;VALUE=DATE-TIME:20230321T134500Z
DTEND;VALUE=DATE-TIME:20230321T141000Z
DTSTAMP;VALUE=DATE-TIME:20241114T092424Z
UID:indico-contribution-171@meetings.aip.de
DESCRIPTION:Speakers: Wyn Evans (Cambridge University)\nWe review estimate
 s of the total mass of the Local Group. High-accuracy proper motions (PMs)
  of M31 and other Local Group (LG) satellites have now been provided by th
 e Gaia satellite. We revisit the timing argument to compute the total mass
  of the LG from the orbit of the Milky Way and M31. We discuss a number of
  systematic effects. The first is caused by the presence of the Large Mage
 llanic Cloud (LMC). The interaction of the LMC with the Milky Way induces 
 a motion toward the LMC. This contribution to the measured velocity of app
 roach of the Milky Way and M31 must be removed. The second is the cosmolog
 ical constant whose effects must be incorporated on these length scales. T
 he third is to allow for cosmic bias and scatter\, pre-conditioned by the 
 accretion history of the LG. Without taking these into account\, the timin
 g argument significantly overestimates the true mass. Adjusting for all th
 ese effects\, we give the estimated mass of the LG for two treatments of M
 31's tangential velocity. The first is $M =3.4^{+1.4}_{−1.1} \\times 10^
 {12}M_⊙$ (68% CL) when using the M31 tangential velocity $82^{+38}_{−3
 5}$ km/s. Lower tangential velocity models with  $59^{+42}_{−38}$ km/s (
 derived from the same PM data with a flat prior on the tangential velocity
 ) lead to an estimated mass of $M=3.1^{+1.3}_{−1.0}×10^{12}M_⊙$ (68% 
 CL). By making an inventory of the total mass associated with the four mos
 t substantial LG members (the Milky Way\, M31\, M33\, and the LMC)\, we es
 timate the known mass to be in the range  $3.7^{+0.5}_{−0.5} \\times 10^
 {12}M_⊙$\n\nhttps://iaus379.aip.de/event/20/contributions/171/
LOCATION:Haus H\, Telegrafenberg
URL:https://iaus379.aip.de/event/20/contributions/171/
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