How Milky Way Satellites operate part1(Aerospace Engineering +Astronomy)
- The spatial distribution of Milky Way satellites, gaps in streams and the nature of dark matter(arXiv)
Author : Mark R. Lovell, Marius Cautun, Carlos S. Frenk, Wojciech A. Hellwing, Oliver Newton
Abstract : The spatial distribution of Milky Way (MW) subhaloes provides an important set of observables for testing cosmological models. These include the radial distribution of luminous satellites, planar configurations, and the abundance of dark subhaloes whose existence or absence is key to distinguishing amongst dark matter models. We use the COCO N-body simulations of cold dark matter (CDM) and 3.3keV thermal relic warm dark matter (WDM) to predict the satellite spatial distribution. We demonstrate that the radial distributions of CDM and 3.3keV-WDM luminous satellites are identical if the minimum pre-infall halo mass to form a galaxy is >108.5M⊙ The distribution of dark subhaloes is significantly more concentrated in WDM due to the absence of low mass, recently accreted substructures that typically inhabit the outer parts of a MW halo in CDM. We show that subhaloes of mass [107,108]M⊙ and within 30kpc of the centre are the stripped remnants of larger haloes in both models. Therefore their abundance in WDM is 3× higher than one would anticipate from the overall WDM subhalo population. We estimate that differences between CDM and WDM concentration — mass relations can be probed for subhalo — stream impact parameters <2kpc. Finally, we find that the impact of WDM on planes of satellites is likely negligible. Precise predictions will require further work with high resolution, self-consistent hydrodynamical simulations
2. Joint constraints on thermal relic dark matter from strong gravitational lensing, the Lyman-αforest, and Milky Way satellites(arXiv)
Author : Wolfgang Enzi, Riccardo Murgia, Oliver Newton, Simona Vegetti, Carlos Frenk, Matteo Viel, Marius Cautun, Christopher D. Fassnacht, Matt Auger, Giulia Despali, John McKean, Léon V. E. Koopmans, Mark Lovell
Abstract : We derive joint constraints on the warm dark matter (WDM) half-mode scale by combining the analyses of a selection of astrophysical probes: strong gravitational lensing with extended sources, the Lyman-α forest, and the number of luminous satellites in the Milky Way. We derive an upper limit of λhm=0.089 Mpc h−1 at the 95 per cent confidence level, which we show to be stable for a broad range of prior choices. Assuming a Planck cosmology and that WDM particles are thermal relics, this corresponds to an upper limit on the half-mode mass of Mhm❤×107 M⊙ h−1, and a lower limit on the particle mass of mth>6.048 keV, both at the 95 per cent confidence level. We find that models with λhm>0.223 Mpc h−1(corresponding to mth>2.552 keV and Mhm<4.8×108 M⊙ h−1) are ruled out with respect to the maximum likelihood model by a factor ≤1/20. For lepton asymmetries L6>10, we rule out the 7.1 keV sterile neutrino dark matter model, which presents a possible explanation to the unidentified 3.55 keV line in the Milky Way and clusters of galaxies. The inferred 95 percentiles suggest that we further rule out the ETHOS-4 model of self-interacting DM. Our results highlight the importance of extending the current constraints to lower half-mode scales. We address important sources of systematic errors and provide prospects for how the constraints of these probes can be improved upon in the future.
3.Weighing Milky Way Satellites with LISA (arXiv)
Author : Valeriya Korol, Vasily Belokurov, Christopher J. Moore, Silvia Toonen
Abstract : White dwarf stars are a well-established tool for studying Galactic stellar populations. Two white dwarfs in a tight binary system offer us an additional messenger — gravitational waves — for exploring the Milky Way and its immediate surroundings. Gravitational waves produced by double white dwarf (DWD) binaries can be detected by the future Laser Interferometer Space Antenna (LISA). Numerous and widespread DWDs have the potential to probe shapes, masses and formation histories of the stellar populations in the Galactic neighbourhood. In this work we outline a method for estimating the total stellar mass of Milky Way satellite galaxies based on the number of DWDs detected by LISA. To constrain the mass we perform a Bayesian inference using binary population synthesis models and considering the number of detected DWDs associated with the satellite and the measured distance to the satellite as the only inputs. Using a fiducial binary population synthesis model we find that for large satellites the stellar masses can be recovered to within 1) a factor two if the star formation history is known and 2) an order of magnitude when marginalising over different star formation history models. For smaller satellites we can place upper limits on their stellar mass. Gravitational wave observations can provide mass measurements for large satellites that are comparable, and in some cases more precise, than standard electromagnetic observations.
