The chemo-dynamical groups of Galactic globular clusters

Monthly Notices of the Royal Astronomical Society, vol. 513, pp. 4107–4129

Abstract

ABSTRACT We introduce a multicomponent chemo-dynamical method for splitting the Galactic population of globular clusters (GCs) into three distinct constituents: bulge, disc, and stellar halo. The latter is further decomposed into the individual large accretion events that built up the Galactic stellar halo: the Gaia–Enceladus–Sausage, Kraken and Sequoia structures, and the Sagittarius and Helmi streams. Our modelling is extensively tested using mock GC samples constructed from the auriga suite of hydrodynamical simulations of Milky Way (MW)-like galaxies. We find that, on average, a proportion of the accreted GCs cannot be associated with their true infall group and are left ungrouped, biasing our recovered population numbers to $\sim 80{{\ \rm per\ cent}}$ of their true value. Furthermore, the identified groups have a completeness and a purity of only $\sim 65{{\ \rm per\ cent}}$. This reflects the difficulty of the problem, a result of the large degree of overlap in energy-action space of the debris from past accretion events. We apply the method to the Galactic data to infer, in a statistically robust and easily quantifiable way, the GCs associated with each MW accretion event. The resulting groups’ population numbers of GCs, corrected for biases, are then used to infer the halo and stellar masses of the now defunct satellites that built up the halo of the MW.

Authors 6

1. Thomas M. Callingham corresponding

   University of Groningen · Durham University

   Affiliation as printed

   Institute of Computational Cosmology, Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK

   Kapteyn Astronomical Institute, University of Groningen, Landeleven 12, NL-9747 AD Groningen, the Netherlands

2. Marius Cautun Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands

3. Alis J. Deason

   Durham University

   Affiliation as printed

   Institute of Computational Cosmology, Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK

4. Carlos Silvestre Frenk

   Durham University

   Affiliation as printed

   Institute of Computational Cosmology, Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK

5. Robert J. J. Grand

   Universidad de La Laguna · Instituto de Astrofísica de Canarias

   Affiliation as printed

   Departamento de Astrofísica, Universidad de La Laguna, Av. del Astrofísico Francisco Sánchez s/n, E-38206 La Laguna, Tenerife, Spain

   Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain

6. Federico Marinacci

   University of Bologna

   Affiliation as printed

   Department of Physics & Astronomy ‘Augusto Righti’, University of Bologna, via Gobetti 93/2, I-40129 Bologna, Italy