Phase‐Space Distributions of Chemical Abundances in Milky Way–Type Galaxy Halos

[Abridged] Motivated by upcoming data from astrometric and spectroscopicsurveys of the Galaxy, we explore the chemical abundance properties andphase-space distributions in hierarchically-formed stellar halo simulations setin a LambdaCDM Universe. Our sample of Milky-Way type stellar halo simulationsresult in average metallicities that range from [Fe/H] = -1.3 to -0.9, with themost metal poor halos resulting from accretion histories that lack destructivemergers with massive (metal rich) satellites. Our stellar halo metallicitiesincrease with stellar halo mass. The slope of the [Fe/H]-stellar mass trendmimics that of the satellite galaxies that were destroyed to build the halos,implying that the relation propagates hierarchically. All simulated haloscontain a significant fraction of old stellar populations accreted more than 10Gyr ago and in a few cases, some intermediate age populations exist. Incontrast with the Milky Way, many of our simulated stellar halos contain oldstellar populations which are metal rich, originating in the early accretion ofmassive satellites. We suggest that the (metal rich) stellar halo of M31 fallsinto this category, while the more metal poor halo of the Milky Way is lackingin early massive accretion events. Interestingly, our hierarchically-formedstellar halos often have non-negligible metallicity gradients in both [Fe/H]and [alpha/Fe]. These gradients extend a few tens of kpc, and can be as largeas 0.5 dex in [Fe/H] and 0.2 dex in [alpha/Fe]. Finally, we find that chemicalabundances can act as a rough substitute for time of accretion of satellitegalaxies. We propose a criterion for identifying tidal streams spatially byselecting stars with [alpha/Fe] ratios below solar.