Jeans that fit: Weighing the mass of the Milky Way analogues in the ΛCDM universe

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Abstract

The spherical Jeans equation is a widely used tool for dynamical study of gravitating systems in astronomy. Here, we test its efficacy in robustly weighing the mass of Milky Way analogues, given they need not be in equilibrium or even spherical. Utilizing Milky Way stellar haloes simulated in accordance with Λ cold dark matter (ΛCDM) cosmology by Bullock and Johnston and analysing them under the Jeans formalism, we recover the underlying mass distribution of the parent galaxy, within distance r/kpc ε [10, 100], with a bias of ~12 per cent and a dispersion of ~14 per cent. Additionally, the mass profiles of triaxial dark matter haloes taken from the SURFS simulation, within scaled radius 0.2 < r/rmax < 3, are measured with a bias of ~-2.4 per cent and a dispersion of ~10 per cent. The obtained dispersion is not because of Poisson noise due to small particle numbers as it is twice the later. We interpret the dispersion to be due to the inherent nature of the λCDM haloes, for example being aspherical and out-of-equilibrium. Hence, the dispersion obtained for stellar haloes sets a limit of about 12 per cent (after adjusting for random uncertainty) on the accuracy with which the mass profiles of the Milky Way-like galaxies can be reconstructed using the spherical Jeans equation. This limit is independent of the quantity and quality of the observational data. The reason for a non-zero bias is not clear, hence its interpretation is not obvious at this stage.

Original languageEnglish
Pages (from-to)4434-4449
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume475
Issue number4
DOIs
Publication statusPublished - 21 Apr 2018

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dark matter
universe
analogs
halos
Milky Way Galaxy
cosmology
astronomy
profiles
mass distribution
adjusting
cold
galaxies
formalism
radii
simulation

Cite this

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title = "Jeans that fit: Weighing the mass of the Milky Way analogues in the ΛCDM universe",
abstract = "The spherical Jeans equation is a widely used tool for dynamical study of gravitating systems in astronomy. Here, we test its efficacy in robustly weighing the mass of Milky Way analogues, given they need not be in equilibrium or even spherical. Utilizing Milky Way stellar haloes simulated in accordance with Λ cold dark matter (ΛCDM) cosmology by Bullock and Johnston and analysing them under the Jeans formalism, we recover the underlying mass distribution of the parent galaxy, within distance r/kpc ε [10, 100], with a bias of ~12 per cent and a dispersion of ~14 per cent. Additionally, the mass profiles of triaxial dark matter haloes taken from the SURFS simulation, within scaled radius 0.2 < r/rmax < 3, are measured with a bias of ~-2.4 per cent and a dispersion of ~10 per cent. The obtained dispersion is not because of Poisson noise due to small particle numbers as it is twice the later. We interpret the dispersion to be due to the inherent nature of the λCDM haloes, for example being aspherical and out-of-equilibrium. Hence, the dispersion obtained for stellar haloes sets a limit of about 12 per cent (after adjusting for random uncertainty) on the accuracy with which the mass profiles of the Milky Way-like galaxies can be reconstructed using the spherical Jeans equation. This limit is independent of the quantity and quality of the observational data. The reason for a non-zero bias is not clear, hence its interpretation is not obvious at this stage.",
keywords = "Galaxy: halo, Galaxy: kinematics and dynamics",
author = "Kafle, {Prajwal R.} and Sanjib Sharma and Robotham, {Aaron S.G.} and Elahi, {Pascal J.} and Driver, {Simon P.}",
year = "2018",
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T1 - Jeans that fit

T2 - Weighing the mass of the Milky Way analogues in the ΛCDM universe

AU - Kafle, Prajwal R.

AU - Sharma, Sanjib

AU - Robotham, Aaron S.G.

AU - Elahi, Pascal J.

AU - Driver, Simon P.

PY - 2018/4/21

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N2 - The spherical Jeans equation is a widely used tool for dynamical study of gravitating systems in astronomy. Here, we test its efficacy in robustly weighing the mass of Milky Way analogues, given they need not be in equilibrium or even spherical. Utilizing Milky Way stellar haloes simulated in accordance with Λ cold dark matter (ΛCDM) cosmology by Bullock and Johnston and analysing them under the Jeans formalism, we recover the underlying mass distribution of the parent galaxy, within distance r/kpc ε [10, 100], with a bias of ~12 per cent and a dispersion of ~14 per cent. Additionally, the mass profiles of triaxial dark matter haloes taken from the SURFS simulation, within scaled radius 0.2 < r/rmax < 3, are measured with a bias of ~-2.4 per cent and a dispersion of ~10 per cent. The obtained dispersion is not because of Poisson noise due to small particle numbers as it is twice the later. We interpret the dispersion to be due to the inherent nature of the λCDM haloes, for example being aspherical and out-of-equilibrium. Hence, the dispersion obtained for stellar haloes sets a limit of about 12 per cent (after adjusting for random uncertainty) on the accuracy with which the mass profiles of the Milky Way-like galaxies can be reconstructed using the spherical Jeans equation. This limit is independent of the quantity and quality of the observational data. The reason for a non-zero bias is not clear, hence its interpretation is not obvious at this stage.

AB - The spherical Jeans equation is a widely used tool for dynamical study of gravitating systems in astronomy. Here, we test its efficacy in robustly weighing the mass of Milky Way analogues, given they need not be in equilibrium or even spherical. Utilizing Milky Way stellar haloes simulated in accordance with Λ cold dark matter (ΛCDM) cosmology by Bullock and Johnston and analysing them under the Jeans formalism, we recover the underlying mass distribution of the parent galaxy, within distance r/kpc ε [10, 100], with a bias of ~12 per cent and a dispersion of ~14 per cent. Additionally, the mass profiles of triaxial dark matter haloes taken from the SURFS simulation, within scaled radius 0.2 < r/rmax < 3, are measured with a bias of ~-2.4 per cent and a dispersion of ~10 per cent. The obtained dispersion is not because of Poisson noise due to small particle numbers as it is twice the later. We interpret the dispersion to be due to the inherent nature of the λCDM haloes, for example being aspherical and out-of-equilibrium. Hence, the dispersion obtained for stellar haloes sets a limit of about 12 per cent (after adjusting for random uncertainty) on the accuracy with which the mass profiles of the Milky Way-like galaxies can be reconstructed using the spherical Jeans equation. This limit is independent of the quantity and quality of the observational data. The reason for a non-zero bias is not clear, hence its interpretation is not obvious at this stage.

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KW - Galaxy: kinematics and dynamics

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