The orbital PDF: the dynamical state of Milky Way sized haloes and the intrinsic uncertainty in the determination of their masses

Han, Jiaxin; Wang, Wenting; Cole, Shaun; Frenk, Carlos S.

doi:10.1093/mnras/stv2522

Cited by 24 publications

(34 citation statements)

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“…Throughout this paper, we do not include particles belonging to subhaloes in our tracer sample. A thorough discussion of the influence of subhaloes can be found in Han et al (2016b).…”

Section: S I M U L At I O N S a N D T R Ac E R Smentioning

confidence: 99%

“…Previously, Han et al (2016b) have analysed five out of the six haloes (labelled halo A to halo E in the Aquarius convention) with the same oPDF method, using both the tagged star particles and dark matter particles as dynamical tracers. In our analysis, we do not directly use the Aquarius suite of simulations, but we make direct comparisons with Han et al (2016b).…”

Section: The Aquarius and The Mock Stellar Halo Simulationsmentioning

confidence: 99%

“…In our analysis, we do not directly use the Aquarius suite of simulations, but we make direct comparisons with Han et al (2016b). There are 2 to 5 × 10 5 star particles in the Aquarius stellar haloes.…”

Section: The Aquarius and The Mock Stellar Halo Simulationsmentioning

confidence: 99%

“…The parameters A and B can be equivalently converted to the mass and concentration parameters of the halo following Han et al (2016b). In the following analysis, we always work in the mass and concentration parameter space and present the results accordingly.…”

Section: E T H O D O L O G Ymentioning

confidence: 99%

“…This clean method allowed us to further investigate how the two assumptions hold when it is applied to Aquarius haloes (Han et al 2016b). We found dark matter particles are more relaxed than stars.…”

Section: Introductionmentioning

confidence: 99%

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What to expect from dynamical modelling of galactic haloes

Wang

Han

Cole

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Many dynamical models of the Milky Way halo require assumptions that the distribution function of a tracer population should be independent of time (i.e., a steady state distribution function) and that the underlying potential is spherical. We study the limitations of such modelling by applying a general dynamical model with minimal assumptions to a large sample of galactic haloes from cosmological N -body and hydrodynamical simulations. Using dark matter particles as dynamical tracers, we find that the systematic uncertainties in the measured mass and concentration parameters typically have an amplitude of 25% to 40%. When stars are used as tracers, however, the systematic uncertainties can be as large as a factor of 2 − 3. The systematic uncertainties are not reduced by increasing the tracer sample size and vary stochastically from halo to halo. These systematic uncertainties are mostly driven by underestimated statistical noise caused by correlated phase-space structures that violate the steady state assumption. The number of independent phase-space structures inferred from the uncertainty level sets a limiting sample size beyond which a further increase no longer significantly improves the accuracy of dynamical inferences. The systematic uncertainty level is determined by the halo merger history, the shape and environment of the halo. Our conclusions apply generally to any spherical steady-state model.

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“…Throughout this paper, we do not include particles belonging to subhaloes in our tracer sample. A thorough discussion of the influence of subhaloes can be found in Han et al (2016b).…”

Section: S I M U L At I O N S a N D T R Ac E R Smentioning

confidence: 99%

Section: The Aquarius and The Mock Stellar Halo Simulationsmentioning

confidence: 99%

Section: The Aquarius and The Mock Stellar Halo Simulationsmentioning

confidence: 99%

Section: E T H O D O L O G Ymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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What to expect from dynamical modelling of galactic haloes

Wang

Han

Cole

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The mass of our Milky Way

Wang¹,

Han²,

Cautun³

et al. 2020

Sci. China Phys. Mech. Astron.

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122

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We perform an extensive review of the numerous studies and methods used to determine the total mass of the Milky Way. We group the various studies into seven broad classes according to their modeling approaches. The classes include: i) estimating Galactic escape velocity using high velocity objects; ii) measuring the rotation curve through terminal and circular velocities; iii) modeling halo stars, globular clusters and satellite galaxies with the Spherical Jeans equation and iv) with phase-space distribution functions; v) simulating and modeling the dynamics of stellar streams and their progenitors; vi) modeling the motion of the Milky Way, M31 and other distant satellites under the framework of Local Group timing argument; and vii) measurements made by linking the brightest Galactic satellites to their counterparts in simulations. For each class of methods, we introduce their theoretical and observational background, the method itself, the sample of available tracer objects, model assumptions, uncertainties, limits and the corresponding measurements that have been achieved in the past. Both the measured total masses within the radial range probed by tracer objects and the extrapolated virial masses are discussed and quoted. We also discuss the role of modern numerical simulations in terms of helping to validate model assumptions, understanding systematic uncertainties and calibrating the measurements. While measurements in the last two decades show a factor of two scatters, recent measurements using Gaia DR2 data are approaching a higher precision. We end with a detailed discussion of future developments in the field, especially as the size and quality of the observational data will increase tremendously with current and future surveys. In such cases, the systematic uncertainties will be dominant and thus will necessitate a much more rigorous testing and characterization of the various mass determination methods.

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Satellite galaxies as better tracers of the Milky Way halo mass

Han

Wang

2019

Proc. IAU

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The inference of the Milky Way halo mass requires modelling the phase space structure of dynamical tracers, with different tracers following different models and having different levels of sensitivity to the halo mass. For steady-state models, deviations from steady-state in the tracer distribution lead to an irreducible stochastic bias. This bias is small for satellite galaxies and dark matter particles, but as large as a factor of 2 for halo stars. This is consistent with the picture that satellite galaxies closely trace the underlying phase space distribution of dark matter particles, while halo stars are less phase-mixed. As a result, the use of only ~100 satellite galaxies can achieve a significantly higher accuracy than that achievable with a much larger sample of halo stars.

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The orbital PDF: the dynamical state of Milky Way sized haloes and the intrinsic uncertainty in the determination of their masses

Cited by 24 publications

References 50 publications

What to expect from dynamical modelling of galactic haloes

What to expect from dynamical modelling of galactic haloes

The mass of our Milky Way

Satellite galaxies as better tracers of the Milky Way halo mass

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