Creating mock catalogues of stellar haloes from cosmological simulations

Abstract

We present a new technique for creating mock catalogues of the individual stars that make up the accreted component of stellar haloes in cosmological simulations and show how the catalogues can be used to test and interpret observational data. The catalogues are constructed from a combination of methods. A semi-analytic galaxy formation model is used to calculate the star formation history in haloes in an Nbody simulation and dark matter particles are tagged with this stellar mass. The tags are converted into individual stars using a stellar population synthesis model to obtain the number density and evolutionary stage of the stars, together with a phasespace sampling method that distributes the stars while ensuring that the phase-space structure of the original N -body simulation is maintained. A set of catalogues based on the ΛCDM Aquarius simulations of Milky Way mass haloes have been created and made publicly available on a website. Two example applications are discussed that demonstrate the power and flexibility of the mock catalogues. We show how the rich stellar substructure that survives in the stellar halo precludes a simple measurement of its density profile and demonstrate explicitly how pencil-beam surveys can return almost any value for the slope of the profile. We also show that localized variations in the abundance of particular types of stars, a signature of differences in the composition of stellar populations, allow streams to be easily identified.

Push it to the limit: Local Group constraints on high-redshift stellar mass functions forM⋆≥ 105 M⊙

“…A more important concern is that more satellites will be completely destroyed when the disk potential is included, thus liberating their stars to the stellar halo (e.g., Bullock & Johnston 2005). Given that the total stellar mass of the Milky Way's stellar halo is quite modest (∼ 10 9 M ) compared to the integrated mass of the stellar mass functions shown in, e.g., Figure 2, there is not much room to hide additional mass in tidally destroyed galaxies that are not already accounted for in current N-body based models (Lowing et al 2015). More work needs to be done in order to solidify this expectation (see, e.g.…”

The Galaxy in Context: Structural, Kinematic, and Integrated Properties

“…Deason et al (2013) use simulations to show that a distinct density break may be related to the accumulation of stars at their apocenters, following relatively massive accretion events. Lowing et al (2014) point out that the measured density parameters depend strongly on the surveyed sightlines and halo accretion history.…”

Glow in the Dark Matter: Observing Galactic Halos with Scattered Light

“…Hence the spectrum from dust-scattering peaks in the ultra-violet (UV) range [27,29]. Since the stellar halo is composed mainly of older stars [34][35][36][37] we have assumed that the spectrum is that of a typical red star i.e. a black body with a temperature of 5000K, while for the disc we assume a black body with a temperature of 6000K, similar to the Sun.…”