We use cosmological hydrodynamical simulations of the APOSTLE project toexamine the fraction of baryons in $\Lambda$CDM haloes that collect intogalaxies. This `galaxy formation efficiency' correlates strongly and withlittle scatter with halo mass, dropping steadily towards dwarf galaxies. Thebaryonic mass of a galaxy may thus be used to place a lower limit on total halomass and, consequently, on its asymptotic maximum circular velocity. A numberof dwarfs seem to violate this constraint, having baryonic masses up to tentimes higher than expected from their rotation speeds, or, alternatively,rotating at only half the speed expected for their mass. Taking the data atface value, either these systems have formed galaxies with extraordinaryefficiency - highly unlikely given their shallow potential wells - or theyinhabit haloes with extreme deficits in their dark matter content. This`missing dark matter' is reminiscent of the inner mass deficits of galaxieswith slowly-rising rotation curves, but extends to regions larger than theluminous galaxies themselves, disfavouring explanations based on starformation-induced `cores' in the dark matter. An alternative could be thatgalaxy inclination errors have been underestimated, and that these are justsystems where inferred mass profiles have been compromised by systematicuncertainties in interpreting the velocity field. This should be investigatedfurther, since it might provide a simple explanation not only formissing-dark-matter galaxies but also for other challenges to our understandingof the inner structure of cold dark matter haloes.

We study the chemodynamical properties of the Carina dwarf spheroidal bycombining an intermediate spectroscopic resolution dataset of more than 900 redgiant and red clump stars, with high-precision photometry to derive theatmospheric parameters, metallicities and age estimates for our targets. Withinthe red giant branch population, we find evidence for the presence of threedistinct stellar sub-populations with different metallicities, spatialdistributions, kinematics and ages. As in the Fornax and Sculptor dwarfspheroidals, the subpopulation with the lowest average metallicity is moreextended and kinematically hotter than all other populations. However, weidentify an inversion in the parallel ordering of metallicity, kinematics andcharacteristic length scale in the two most metal rich subpopulations, whichtherefore do not contribute to a global negative chemical gradient. Contrary tocommon trends in the chemical properties with radius, the metal richestpopulation is more extended and mildly kinematically hotter than the maincomponent of intermediate metallicity. More investigations are required toascertain the nature of this inversion, but we comment on the mechanisms thatmight have caused it.