Two-integral distribution functions in axisymmetric galaxies: Implications for dark matter searches

Petač, Mihael; Ullio, Piero

doi:10.1103/physrevd.99.043003

Cited by 15 publications

(26 citation statements)

References 57 publications

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“…In particular, we will adopt the numerical approach developed by Hunter & Qian [69,75], that relies on theoretical foundations previously laid out by Lynden-Bell [76]. Until recently, the method was applied only to stellar systems, while it was for the first time systematically studied in the context of DM in [70]. We refer the reader to the above references for the proof of the method and detailed discussions regarding its numerical implementation.…”

Section: Axisymmetric Inversion Methodsmentioning

confidence: 99%

Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulations

Petač,

Lavalle,

Núñez-Castiñeyra

et al. 2021

Preprint

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Signal predictions for galactic dark matter (DM) searches often rely on assumptions on the DM phase-space distribution function (DF) in halos. This applies to both particle (e.g. p-wave suppressed or Sommerfeld-enhanced annihilation, scattering off atoms, etc.) and macroscopic DM candidates (e.g. microlensing of primordial black holes). As experiments and observations improve in precision, better assessing theoretical uncertainties becomes pressing in the prospect of deriving reliable constraints on DM candidates or trustworthy hints for detection. Most reliable predictions of DFs in halos are based on solving the steady-state collisionless Boltzmann equation (e.g. Eddingtonlike inversions, action-angle methods, etc.) consistently with observational constraints. One can do so starting from maximal symmetries and a minimal set of degrees of freedom, and then increasing complexity. Key issues are then whether adding complexity, which is computationally costy, improves predictions, and if so where to stop. Clues can be obtained by making predictions for zoomed-in hydrodynamical cosmological simulations in which one can access the true (coarse-grained) phase-space information. Here, we test an axisymmetric extension of the Eddington inversion to predict the full DM DF from its density profile and the total gravitational potential of the system. This permits to go beyond spherical symmetry, and is a priori well suited for spiral galaxies. We show that axisymmetry does not necessarily improve over spherical symmetry because the (observationally unconstrained) angular momentum of the DM halo is not generically aligned with the baryonic one. Theoretical errors are similar to those of the Eddington inversion though, at the 10-20% level for velocity-dependent predictions related to particle DM searches in spiral galaxies. We extensively describe the approach and comment on the results.

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Section: Axisymmetric Inversion Methodsmentioning

confidence: 99%

Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulations

Petač,

Lavalle,

Núñez-Castiñeyra

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…In particular, we will adopt a numerically friendly approach developed by Hunter & Qian [53,54], that relies on theoretical foundations previously lied out by Lynden-Bell [55]. Until recently, the method was applied only to stellar systems, while it was for the first time systematically studied it in the context of DM in [32]. We refer the reader to these previous publications for the proof of the inversion method and detailed discussions regarding its implementation.…”

Section: A Two-integral Distribution Functionmentioning

confidence: 99%

“…Following the Bayesian approach, we use Monte-Carlo Markov Chain (MCMC) sampling to simultaneously fit the DM distribution as well as the baryonic gravitational potential to a set of the latest kinematic constraints. This, in turn, allows us to self-consistently compute equilibrium two-integral phasespace distribution function (PSDF) for the galactic DM through a computationally efficient method previously explored in [32]. It is important to note that our approach provides an accurate description only for DM particles that have reached dynamical equilibrium.…”

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confidence: 99%

Equilibrium axisymmetric halo model for the Milky Way and its implications for direct and indirect DM searches

Petac

2020

Preprint

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We for the first time provide self-consistent axisymmetric phase-space distribution models for the Milky Way's dark matter (DM) halo which are carefully matched against the latest kinematic measurements through Bayesian analysis. By using broad priors on the individual galactic components, we derive conservative estimates for the astrophysical factors entering the interpretation of direct and indirect DM searches. While the resulting DM density profiles are in good agreement with previous studies, implying ρ ≈ 10 −2 M /pc 3 , the presence of baryonic disc leads to significant differences in the local DM velocity distribution in comparison with the spherical models. For direct detection, this implies roughly 30% stronger cross-section limits at DM masses near detectors maximum sensitivity and up to an order of magnitude weaker limits at the lower end of the mass range. Furthermore, by performing Monte-Carlo simulations for the upcoming Darwin and DarkSide 20k experiments, we demonstrate that upon successful detection of heavy DM with coupling just below the current limits, the carefully constructed axisymmetric models can eliminate bias and reduce uncertainties by up to 40% in the reconstructed DM coupling and mass, but also help in a more reliable determination of the scattering operator. Furthermore, the velocity anisotropies induced by the baryonic disc, as well as halo rotation, can lead to significantly larger annual modulation amplitude and sizeable differences in the directional distribution of the expected DM-induced events. For indirect searches, we provide the differential J-factors and compute several moments of the relative velocity distribution that are needed for computing the rate of velocity-dependent annihilations. However, accurate predictions are still hindered by large uncertainties regarding the central DM distribution.

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“…In a self-consistent model of the Milky Way, the astrophysical parameters ρ χ , v 0 and v esc will not be independent [9,10,14,35]. However, given both the variation between different observations and the large uncertainties of individual measurements, for simplicity we ignore correlations between astrophysical parameters in the SHM.…”

Section: )mentioning

confidence: 99%

Uncertainties in direct dark matter detection in light of Gaia's escape velocity measurements

Freese

Kelso

et al. 2019

J. Cosmol. Astropart. Phys.

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Direct detection experiments have set increasingly stringent limits on the cross section for spin-independent dark matter-nucleon interactions. In obtaining such limits, experiments primarily assume the standard halo model (SHM) as the distribution of dark matter in our Milky Way. Three astrophysical parameters are required to define the SHM: the local dark matter escape velocity, the local dark matter density and the circular velocity of the sun around the center of the galaxy. This paper studies the effect of the uncertainties in these three astrophysical parameters on the XENON1T exclusion limits using the publicly available DDCalc code. We compare limits obtained using the widely assumed escape velocity from the RAVE survey and the newly calculated escape velocity by Monari et al. using Gaia data. Our study finds that the astrophysical uncertainties are dominated by the uncertainty in the escape velocity (independent of the best fit value) at dark matter masses below 6 GeV and can lead to a variation of nearly 6 orders of magnitude in the exclusion limits at 4 GeV. Above a WIMP mass of 6 GeV, the uncertainty becomes dominated by the local dark matter density, leading to uncertainties of factors of ∼10 (3) at 6 (15) GeV WIMP mass in the exclusion limits. Additionally, this work finds that the updated best fit value for the escape velocity based on Gaia data leads to only very minor changes to the effects of the astrophysical uncertainties on the XENON1T exclusion limits.ArXiv ePrint: 1904.04781

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Two-integral distribution functions in axisymmetric galaxies: Implications for dark matter searches

Cited by 15 publications

References 57 publications

Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulations

Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulations

Equilibrium axisymmetric halo model for the Milky Way and its implications for direct and indirect DM searches

Uncertainties in direct dark matter detection in light of Gaia's escape velocity measurements

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