Accreted stellar populations are comprised of the remnants of destroyed galaxies, and often dominate the ‘stellar haloes’ of galaxies such as the Milky Way (MW). This ensemble of external contributors is a key indicator of the past assembly history of a galaxy. We introduce a novel statistical method that uses the unbinned metallicity distribution function (MDF) of a stellar population to estimate the mass spectrum of its progenitors. Our model makes use of the well-known mass–metallicity relation of galaxies and assumes Gaussian MDF distributions for individual progenitors: the overall MDF is thus a mixture of MDFs from smaller galaxies. We apply the method to the stellar halo of the MW, as well as the classical MW satellite galaxies. The stellar components of the satellite galaxies have relatively small sample sizes, but we do not find any evidence for accreted populations with L > Lhost/100. We find that the MW stellar halo has N ∼ 1−3 massive progenitors (L ≳ 108L⊙) within 10 kpc, and likely several hundred progenitors in total. We also test our method on simulations of MW-mass haloes, and find that our method is able to recover the true accreted population within a factor of 2. Future datamore »
Using action space clustering to constrain the recent accretion history of Milky Way-like galaxies
ABSTRACT In the currently favoured cosmological paradigm galaxies form hierarchically through the accretion of satellites. Since a satellite is less massive than the host, its stars occupy a smaller volume in action space. Actions are conserved when the potential of the host halo changes adiabatically, so stars from an accreted satellite would remain clustered in action space as the host evolves. In this paper, we identify recently disrupted accreted satellites in three Milky Way-like disc galaxies from the cosmological baryonic FIRE-2 simulations by tracking satellites through simulation snapshots. We try to recover these satellites by applying the cluster analysis algorithm Enlink to the orbital actions of accreted star particles in the z = 0 snapshot. Even with completely error-free mock data we find that only 35 per cent (14/39) satellites are well recovered while the rest (25/39) are poorly recovered (i.e. either contaminated or split up). Most (10/14 ∼70 per cent) of the well-recovered satellites have infall times <7.1 Gyr ago and total mass >4 × 108M⊙ (stellar mass more than 1.2 × 106 M⊙, although our upper mass limit is likely to be resolution dependent). Since cosmological simulations predict that stellar haloes include a population of in situ stars, we test our ability to recover satellites when the data more »
- Publication Date:
- NSF-PAR ID:
- 10327063
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 509
- Issue:
- 4
- Page Range or eLocation-ID:
- 5882 to 5901
- ISSN:
- 0035-8711
- Sponsoring Org:
- National Science Foundation
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Unravelling the mass spectrum of destroyed dwarf galaxies with the metallicity distribution function
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ABSTRACT In order to backward integrate the orbits of Milky Way (MW) dwarf galaxies, much effort has been invested in recent years to constrain their initial phase-space coordinates. Yet equally important are the assumptions on the potential that the dwarf galaxies experience over time, especially given the fact that the MW is currently accreting the Large Magellanic Cloud (LMC). In this work, using a dark-matter-only zoom-in simulation, we test whether the use of common parametric forms of the potential is adequate to successfully backward integrate the orbits of the subhaloes from their present-day positions. We parametrize the recovered orbits and compare them with those from the simulations. We find that simple symmetric parametric forms of the potential fail to capture the complexities and the inhomogeneities of the true potential experienced by the subhaloes. More specifically, modelling a recent massive accretion like that of the LMC as a sum of two spherical parametric potentials leads to substantial errors in the recovered parameters of the orbits. These errors rival those caused due to (a) a 30 per cent uncertainty in the virial mass of the MW and (b) not modelling the potential of the recently accreted massive satellite. Our work suggests that (i) themore »
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Accepted Manuscript1.0
- Publisher's Version of Record
- https://doi.org/10.1093/mnras/stab3306
