dc.contributor.author Benisty, D dc.contributor.author Vasiliev, E dc.contributor.author Evans, NW dc.contributor.author Davis, AC dc.contributor.author Hartl, OV dc.contributor.author Strigari, LE dc.date.accessioned 2022-03-28T19:04:17Z dc.date.available 2022-03-28T19:04:17Z dc.date.issued 2022 dc.date.submitted 2022-01-29 dc.identifier.issn 2041-8205 dc.identifier.other apjlac5c42 dc.identifier.other ac5c42 dc.identifier.other aas37419 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/335370 dc.description.abstract High accuracy proper motions (PMs) of M31 and other Local Group satellites have now been provided by the {\it Gaia} satellite. We revisit the Timing Argument to compute the total mass $M$ of the Local Group from the orbit of the Milky Way and M31, allowing for the Cosmological Constant. We rectify for a systematic effect caused by the presence of the Large Magellanic Cloud (LMC). The interaction of the LMC with the Milky Way induces a motion towards the LMC. This contribution to the measured velocity of approach of the Milky Way and M31 must be removed. We allow for cosmic bias and scatter by extracting correction factors tailored to the accretion history of the Local Group. The distribution of correction factors is centered around $0.63$ with a scatter $\pm 0.2$, indicating that the Timing Argument significantly overestimates the true mass. Adjusting for all these effects, the estimated mass of the Local Group is $M = 3.4^{+1.4}_{-1.1} \times 10^{12} M_{\odot}$ (68 % CL) when using the M31 tangential velocity $82^{+38}_{-35}$ 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 $M = 3.1^{+1.3}_{-1.0} \times 10^{12} M_{\odot}$ (68 % CL). By making an inventory of the total mass associated with the 4 most substantial LG members (the Milky Way, M31, M33 and the LMC), we estimate the known mass is in the range $3.7^{+0.5}_{-0.5} \times 10^{12} \, M_{\odot}$. dc.language en dc.publisher American Astronomical Society dc.subject astro-ph.GA dc.subject astro-ph.GA dc.subject astro-ph.CO dc.subject astro-ph.HE dc.subject gr-qc dc.title The Local Group Mass in the Light of Gaia dc.type Article dc.date.updated 2022-03-28T19:04:16Z prism.issueIdentifier 1 prism.publicationName Astrophysical Journal Letters prism.volume 928 dc.identifier.doi 10.17863/CAM.82799 dcterms.dateAccepted 2022-03-10 rioxxterms.versionofrecord 10.3847/2041-8213/ac5c42 rioxxterms.version VoR rioxxterms.licenseref.uri http://creativecommons.org/licenses/by/4.0/ dc.contributor.orcid Benisty, D [0000-0002-9578-3081] dc.contributor.orcid Vasiliev, E [0000-0002-5038-9267] dc.contributor.orcid Strigari, LE [0000-0001-5672-6079] dc.identifier.eissn 2041-8213 dc.publisher.url http://dx.doi.org/10.3847/2041-8213/ac5c42 cam.issuedOnline 2022-03-21
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