Identifying the possible ex-situ origin of the globular clusters of the Milky Way: A kinematic study

Abstract

This is the second paper in a series, which studies the likelihood that some globular clusters (GCs) of the Milky Way (MW) could have originated from a dwarf satellite galaxy (DSG). Using a large suite of three-body simulations we determine the present-day orbital properties of 154 GCs that could have escaped from 41 MW DSGs over the past $8\mathrm{Gyrs}$. For the MW we considered two sets of static and dynamic models which account for the sustained growth of the MW since its birth. We focus on the Magellanic Clouds and Sagittarius. We compare the apogalactic distance, eccentricity, and orbital inclination of the MW GCs with those of runaway GCs from DSGs, to constrain their possible ex-situ origin. We observe a positive correlation between a DSG mass and the dispersion of its runaway GCs in the orbital parameter space of ($R_{\mathrm{ap}}$, $e$). We provide tables of the identified MW GCs and their likely associated progenitors. In total, we find 29 (19%) MW GCs which could be kinematically associated with MW DSGs. We report, for the first time, 6 and 10 new associations with the Large Magellanic Cloud and the Sagittarius, respectively. For the Sagittarius we predict a concentration of runaway GCs at large apogalactic distances of $R_{\mathrm{ap}}\approx 275-375\mathrm{kpc}$, $e\approx 0.8$, and a relative inclination of $\Delta \theta \approx 20^{\circ }$. So far, there has not been any observed GCs with such orbital elements. Complemented with photometric and spectroscopic observations, and cosmological simulations, the findings from the present study could conclusively settle the debate over the in-situ vs. ex-situ origin of the MW GCs.

20 pages, 16 figures, 5 tables, references amended. Accepted for publication in MNRAS

References in corpus (16)

• galpy: A Python Library for Galactic Dynamics
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• Building Late-Type Spiral Galaxies by In-Situ and Ex-Situ Star Formation
• Hydra II: a faint and compact Milky Way dwarf galaxy found in the Survey of the Magellanic Stellar History
• Public data release of the FIRE-2 cosmological zoom-in simulations of galaxy formation
• The last breath of the Sagittarius dSph
• A Tail of Two Populations: Chemo-dynamics of the Sagittarius Stream and Implications for its Original Mass
• Revised and new proper motions for confirmed and candidate Milky Way dwarf galaxies
• Search for 511 keV Emission in Satellite Galaxies of the Milky Way with INTEGRAL/SPI
• Chemical abundances of giant stars in NGC 5053 and NGC 5634, two globular clusters associated with the Sagittarius dwarf Spheroidal galaxy?
• The globular cluster AM 4: yet another young globular associated with the Sgr Dwarf Spheroidal galaxy?
• Dynamical Constraints on the Origin of Multiple Stellar Populations in Globular Clusters
• A DECam View of the Diffuse Dwarf Galaxy Crater II: Variable Stars
• Origin of structural and kinematical properties of the Small Magellanic Cloud
• Galactic orbital motions of star clusters: static versus semicosmological time-dependent Galactic potentials
• The globular cluster system of the isolated elliptical NGC 6411: An old system in an intermediate-age galaxy?

Cited by in corpus (2)

• A Pristine-UNIONS view on the Galaxy: Kinematics of the distant spur feature of the Sagittarius stream traced by Blue Horizontal Branch stars
• Dark Star Clusters or Ultra-Faint Dwarf galaxies? Revisiting UMa3/U1