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The mass distribution and assembly of the Milky Way from the properties of the Magellanic Clouds


Busha, M T; Marshall, P J; Wechsler, R H; Klypin, A; Primack, J (2011). The mass distribution and assembly of the Milky Way from the properties of the Magellanic Clouds. Astrophysical Journal, 743(1):40.

Abstract

We present a new measurement of the mass of the Milky Way (MW) based on observed properties of its largest satellite galaxies, the Magellanic Clouds (MCs), and an assumed prior of a ΛCDM universe. The large, high-resolution Bolshoi cosmological simulation of this universe provides a means to statistically sample the dynamical properties of bright satellite galaxies in a large population of dark matter halos. The observed properties of the MCs, including their circular velocity, distance from the center of the MW, and velocity within the MW halo, are used to evaluate the likelihood that a given halo would have each or all of these properties; the posterior probability distribution function (PDF) for any property of the MW system can thus be constructed. This method provides a constraint on the MW virial mass, 1.2+0.7 – 0.4 (stat.)+0.3 – 0.3 (sys.) × 1012 M ☉ (68% confidence), which is consistent with recent determinations that involve very different assumptions. In addition, we calculate the posterior PDF for the density profile of the MW and its satellite accretion history. Although typical satellites of 1012 M ☉ halos are accreted over a wide range of epochs over the last 10 Gyr, we find a ~72% probability that the MCs were accreted within the last Gyr, and a 50% probability that they were accreted together.

We present a new measurement of the mass of the Milky Way (MW) based on observed properties of its largest satellite galaxies, the Magellanic Clouds (MCs), and an assumed prior of a ΛCDM universe. The large, high-resolution Bolshoi cosmological simulation of this universe provides a means to statistically sample the dynamical properties of bright satellite galaxies in a large population of dark matter halos. The observed properties of the MCs, including their circular velocity, distance from the center of the MW, and velocity within the MW halo, are used to evaluate the likelihood that a given halo would have each or all of these properties; the posterior probability distribution function (PDF) for any property of the MW system can thus be constructed. This method provides a constraint on the MW virial mass, 1.2+0.7 – 0.4 (stat.)+0.3 – 0.3 (sys.) × 1012 M ☉ (68% confidence), which is consistent with recent determinations that involve very different assumptions. In addition, we calculate the posterior PDF for the density profile of the MW and its satellite accretion history. Although typical satellites of 1012 M ☉ halos are accreted over a wide range of epochs over the last 10 Gyr, we find a ~72% probability that the MCs were accreted within the last Gyr, and a 50% probability that they were accreted together.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:December 2011
Deposited On:18 Feb 2012 09:19
Last Modified:05 Apr 2016 15:21
Publisher:IOP Publishing
ISSN:0004-637X (P) 1538-4357 (E)
Publisher DOI:10.1088/0004-637X/743/1/40
Related URLs:http://arxiv.org/abs/1011.2203
Permanent URL: http://doi.org/10.5167/uzh-54810

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