We derive the local dark matter density by applying the integrated Jeans equation method from Silverwood et al. (2016) to SDSS-SEGUE G-dwarf data processed and presented by Büdenbender et al. (2015). We use the MULTINEST Bayesian nested sampling software to fit a model for the baryon distribution, dark matter and tracer stars, including a model for the 'tilt term' that couples the vertical and radial motions, to the data. The α-young population from Büdenbender et al. (2015) yields the most reliable result of ρ dm = 0.46 +0.07 −0.09 GeV cm −3 = 0.012 +0.001 −0.002 M pc −3 . Our analyses yield inconsistent results for the α-young and α-old data, pointing to problems in the tilt term and its modelling, the data itself, the assumption of a flat rotation curve, or the effects of disequilibria.

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Ultracompact minihalos have recently been proposed as a new class of dark matter structure. These minihalos would be produced by phase transitions in the early Universe or features in the inflaton potential, and constitute non-baryonic massive compact halo objects (MACHOs) today. We examine the prospect of detecting ultracompact minihalos in gamma-rays if dark matter consists of self-annihilating particles. We compute present-day fluxes from minihalos produced in the e + e − annihilation epoch, and the QCD and electroweak phase transitions in the early Universe. Even at a distance of 100 pc, minihalos produced during the e + e − epoch should be eminently detectable today, either by the Fermi satellite, current AirČerenkov telescopes, or even in archival EGRET data. Within ∼1 pc, minihalos formed in the QCD phase transition would have similar predicted fluxes to the dwarf spheroidal galaxies targeted by current indirect dark matter searches, so might also be detectable by present or upcoming experiments.PACS numbers: 95.35.+d, 98.70.Rz, 98.80.Cq The identity of dark matter remains one of the key outstanding problems in physics. Weakly-interacting massive particles (WIMPs) provide a compelling solution [1] because their weak-scale masses and cross-sections make for a natural explanation of the observed abundance of dark matter. As most proposed WIMPs are their own antiparticles, high WIMP densities would also lead to high rates of self-annihilation. Annihilation products might then provide indirect evidence of the nature of dark matter. Gamma-rays are particularly attractive in this respect, as they do not suffer the same problems of deflection and attenuation as massive, charged species.It was proposed [2] that dark matter could be massive compact halo objects (MACHOs) of condensed baryons, e.g. brown dwarfs or faint stars. These are ruled out as the dominant component of dark matter by the cosmic microwave background (CMB; [3]), Big Bang Nucleosynthesis [4], and microlensing searches [5]. Primordial black holes (PBHs) are an alternative, disfavoured by their energetic evaporation, gravitational influence [6], and the large primordial density perturbations required for their production (δ 30%). For comparison, the initial density perturbations from inflation were δ ∼ 10 −5 .Ricotti & Gould [7] proposed a non-baryonic MACHO that avoids these constraints, and presents a promising new target for microlensing searches. Formation proceeds similarly to PBHs, whereby small-scale density perturbations in the early Universe collapse to a compact body. A small-scale power spectrum that is the same as observed on large scales [3] provides insufficient power for this to occur. Perturbations could however be enhanced by features in the inflaton potential, or phase transitions in the early Universe [8]. If a perturbation is small, matter will not be sufficiently compressed to form a black hole, leaving only a compact cloud of gas and dark matter. This mechanism requires density contrasts of just δ 10 −3 to proceed, so is fa...