White dwarfs in the building blocks of the Galactic spheroid

Abstract

The galactic halo likely grew over time in part by assembling smaller galaxies, the so-called building blocks. We investigate if the properties of these building blocks are reflected in the halo white dwarf (WD) population in the Solar neighborhood. Furthermore, we compute the halo WD luminosity functions (WDLFs) for four major building blocks of five cosmologically motivated stellar haloes. We couple the SeBa binary population synthesis model to the Munich-Groningen semi-analytic galaxy formation model, applied to the high-resolution Aquarius dark matter simulations. Although the semi-analytic model assumes an instantaneous recycling approximation, we model the evolution of zero-age main sequence stars to WDs, taking age and metallicity variations of the population into account. Although the majority of halo stars is old and metal-poor and therefore the WDs in the different building blocks have similar properties (including present-day luminosity), we find in our models that the WDs originating from building blocks that have young and/or metal-rich stars can be distinguished from WDs that were born in other building blocks. In practice however, it will be hard to prove that these WDs really originate from different building blocks, as the variations in the halo WD population due to binary WD mergers result in similar effects. The five joined stellar halo WD populations that we modelled result in WDLFs that are very similar to each other. We find that simple models with a Kroupa or Salpeter initial mass function (IMF) fit the observed luminosity function slightly better, since the Chabrier IMF is more top-heavy, although this result is dependent on our choice of the stellar halo mass density in the Solar neighborhood.

16 pages, 16 figures, published in Astronomy & Astrophysics

References in corpus (11)

• The hierarchical formation of the brightest cluster galaxies
• The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach
• White dwarf evolutionary sequences for low-metallicity progenitors: The impact of third dredge-up
• Elemental Abundances in Milky Way-like Galaxies from a Hierarchical Galaxy Formation Model
• The oldest and most metal poor stars in the APOSTLE Local Group simulations
• Detecting stars, galaxies, and asteroids with Gaia
• The age-metallicity dependence for white dwarfs
• Creating mock catalogues of stellar haloes from cosmological simulations
• On the common mass scale of the Milky Way satellites
• Binary white dwarfs in the halo of the Milky Way
• Building Blocks of the Milky Way's Accreted Spheroid