scholarly journals The kinematics of globular cluster populations in the E-MOSAICS simulations and their implications for the assembly history of the Milky Way

2021 ◽  
Author(s):  
Sebastian Trujillo-Gomez ◽  
J M Diederik Kruijssen ◽  
Marta Reina-Campos ◽  
Joel L Pfeffer ◽  
Benjamin W Keller ◽  
...  
Keyword(s):  
Dark Matter ◽  
Globular Cluster ◽  
Milky Way ◽  
Detailed Comparison ◽  
History Of ◽  
Low Mass ◽  
Galaxy Assembly ◽  
The Masses ◽  
Kinematic Distribution

Abstract We present a detailed comparison of the Milky Way (MW) globular cluster (GC) kinematics with the 25 Milky Way-mass cosmological simulations from the E-MOSAICS project. While the MW falls within the kinematic distribution of GCs spanned by the simulations, the relative kinematics of its metal-rich ($[\rm {Fe}/\rm {H}]>-1.2$) versus metal-poor ($[\rm {Fe}/\rm {H}]<-1.2$), and inner (r < 8 kpc) versus outer (r > 8 kpc) populations are atypical for its mass. To understand the origins of these features, we perform a comprehensive statistical analysis of the simulations, and find 18 correlations describing the assembly of L* galaxies and their dark matter haloes based on their GC population kinematics. The correlations arise because the orbital distributions of accreted and in-situ GCs depend on the masses and accretion redshifts of accreted satellites, driven by the combined effects of dynamical fraction, tidal stripping, and dynamical heating. Because the kinematics of in-situ/accreted GCs are broadly traced by the metal-rich/metal-poor and inner/outer populations, the observed GC kinematics are a sensitive probe of galaxy assembly. We predict that relative to the population of L* galaxies, the MW assembled its dark matter and stellar mass rapidly through a combination of in-situ star formation, more than a dozen low-mass mergers, and 1.4 ± 1.2 early (z = 3.1 ± 1.3) major mergers. The rapid assembly period ended early, limiting the fraction of accreted stars. We conclude by providing detailed quantitative predictions for the assembly history of the MW.

scholarly journals The Faint Globular Cluster in the Dwarf Galaxy Andromeda I

2017 ◽  
Vol 34 ◽  
Author(s):  
Nelson Caldwell ◽  
Jay Strader ◽  
David J. Sand ◽  
Beth Willman ◽  
Anil C. Seth
Keyword(s):  
Dark Matter ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Dark Matter Halos ◽  
History Of ◽  
Low Mass ◽  
Growing Population

AbstractObservations of globular clusters in dwarf galaxies can be used to study a variety of topics, including the structure of dark matter halos and the history of vigorous star formation in low-mass galaxies. We report on the properties of the faint globular cluster (MV ~ −3.4) in the M31 dwarf galaxy Andromeda I. This object adds to the growing population of low-luminosity Local Group galaxies that host single globular clusters.

scholarly journals Where did the globular clusters of the Milky Way form? Insights from the E-MOSAICS simulations

2020 ◽  
Vol 495 (4) ◽  
pp. 4248-4267 ◽  
Author(s):  
Benjamin W Keller ◽  
J M Diederik Kruijssen ◽  
Joel Pfeffer ◽  
Marta Reina-Campos ◽  
Nate Bastian ◽  
...  
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Milky Way ◽  
Ex Situ ◽  
History Of ◽  
Natural Outcome ◽  
Minor Mergers ◽  
Galaxy Assembly ◽  
Simple Picture

ABSTRACT Globular clusters (GCs) are typically old, with most having formed at z ≳ 2. This makes understanding their birth environments difficult, as they are typically too distant to observe with sufficient angular resolution to resolve GC birth sites. Using 25 cosmological zoom-in simulations of Milky Way-like galaxies from the E-MOSAICS project, with physically motivated models for star formation, feedback, and the formation, evolution, and disruption of GCs, we identify the birth environments of present-day GCs. We find roughly half of GCs in these galaxies formed in situ (52.0 ± 1.0 per cent) between z ≈ 2–4, in turbulent, high-pressure discs fed by gas that was accreted without ever being strongly heated through a virial shock or feedback. A minority of GCs form during mergers (12.6 ± 0.6 per cent in major mergers, and 7.2 ± 0.5 per cent in minor mergers), but we find that mergers are important for preserving the GCs seen today by ejecting them from their natal, high density interstellar medium (ISM), where proto-GCs are rapidly destroyed due to tidal shocks from ISM substructure. This chaotic history of hierarchical galaxy assembly acts to mix the spatial and kinematic distribution of GCs formed through different channels, making it difficult to use observable GC properties to distinguish GCs formed in mergers from ones formed by smooth accretion, and similarly GCs formed in situ from those formed ex situ. These results suggest a simple picture of GC formation, in which GCs are a natural outcome of normal star formation in the typical, gas-rich galaxies that are the progenitors of present-day galaxies.

scholarly journals Kinematical & Chemical Characteristics of the Thin and Thick Disks

2008 ◽  
Vol 4 (S254) ◽  
pp. 179-190 ◽  
Author(s):  
Rosemary F. G. Wyse
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Observational Evidence ◽  
Chemical Characteristics ◽  
Chemical Abundance ◽  
The Galaxy ◽  
History Of ◽  
Thin And Thick Disks ◽  
Thick Disks

AbstractI discuss how the chemical abundance distributions, kinematics and age distributions of stars in the thin and thick disks of the Galaxy can be used to decipher the merger history of the Milky Way, a typical large galaxy. The observational evidence points to a rather quiescent past merging history, unusual in the context of the ‘consensus’ cold-dark-matter cosmology favoured from observations of structure on scales larger than individual galaxies.

Orbits

2018 ◽  
Author(s):  
David M. Wittman
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Milky Way ◽  
Extrasolar Planets ◽  
Binary Star ◽  
Milky Way Galaxy ◽  
Newtonian Model ◽  
Theory Of Gravity ◽  
The Masses ◽  
The Universe

Orbits are ubiquitous in the universe: moons orbit planets, planets orbit stars, stars orbit around the center of the Milky Way galaxy, and so on. Any theory of gravity will have to explain the properties of all these orbits. To pave the way for developing the metric theory of gravity (general relativity) this chapter examines the basics of orbits as observed and as explained by the Newtonian model of gravity. We can use our understanding of gravity to infer the masses and other properties of these cosmic systems. Te chapter concludes with four optional sections in this spirit, covering the slingshot maneuver; dark matter; binary star orbits and how they reveal the masses of stars; and extrasolar planets.

scholarly journals Disk Mass From Large-Scale Dynamics

1998 ◽  
Vol 11 (1) ◽  
pp. 410-411
Author(s):  
J.A. Sellwood
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Stellar Population ◽  
Milky Way ◽  
Low Mass Stars ◽  
Rutgers University ◽  
Disk Mass ◽  
Low Mass ◽  
The Individual ◽  
Inner Parts

The radial distribution of mass in a disk galaxy is strongly constrained by its rotation curve. The separate contributions from the individual stellar populations and dark matter (DM) are not easily disentangled, however, especially since there is generally no feature to indicate where the component dominating the central attraction switches from luminous to dark matter. Here I summarize three recent thesis projects at Rutgers University which all suggest that DM has a low density in the inner parts of bright galaxies, and that most of the mass therefore resides in the disk. In addition, I present some preliminary work on the Milky Way. If we are able to determine the M/L of a typical disk stellar population, it should provide a useful constraint on the numbers of low mass stars.

scholarly journals A universality of dark-halo surface density for the Milky Way and Andromeda dwarf satellites as a probe of the coldness of dark matter

2015 ◽  
Vol 11 (S317) ◽  
pp. 306-307
Author(s):  
Kohei Hayashi ◽  
Masashi Chiba
Keyword(s):  
Dark Matter ◽  
Surface Density ◽  
Milky Way ◽  
Mass Range ◽  
Dark Halo ◽  
Density Profiles ◽  
Dwarf Spheroidal Galaxies ◽  
Galaxy Sample ◽  
Low Mass ◽  
The Mean

AbstractWe propose a new astrophysical test on the nature of dark matter based on the properties of dark halos associated with dwarf spheroidal galaxies. The method adopts a mean surface density of a dark halo defined within a radius of maximum circular velocity, which is derivable for a wide variety of galaxies with any dark-matter density profiles. We find that even though dark halo density profiles are derived based on the different assumptions for each galaxy sample, this surface density is generally constant across a wide mass range of galaxy. We find that at higher halo-mass scales, this constancy for real galaxies can be naturally reproduced by both cold and warm dark matter (CDM and WDM) models. However, at low-mass scales, for which we have estimated from the Milky Way and Andromeda dwarf satellites, the mean surface density derived from WDM models largely deviates from the observed constancy, whereas CDM models are in reasonable agreement with observations.

scholarly journals Origins of Stellar Halos

2015 ◽  
Vol 11 (S317) ◽  
pp. 1-8
Author(s):  
Kathryn V. Johnston
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Stellar Populations ◽  
Observational Evidence ◽  
Dark Matter Halo ◽  
Theoretical Understanding ◽  
Stellar Halo ◽  
The One ◽  
Halo Population

AbstractThis contribution reviews ideas about the origins of stellar halos. It includes discussion of the theoretical understanding of and observational evidence for stellar populations formed “in situ” (meaning formed in orbits close to their current ones), “kicked-out” (meaning formed in the inner galaxy in orbits unlike their current ones) and “accreted” (meaning formed in a dark matter halo other than the one they currently occupy). At this point there is general agreement that a significant fraction of any stellar halo population is likely “accreted”. There is modest evidence for the presence of a “kicked-out” population around both the Milky Way and M31. Our theoretical understanding of and the observational evidence for an “in situ” population are less clear.

scholarly journals Probing the nature of dark matter with accreted globular cluster streams

2020 ◽  
Vol 501 (1) ◽  
pp. 179-200 ◽  
Author(s):  
Khyati Malhan ◽  
Monica Valluri ◽  
Katherine Freese
Keyword(s):  
Dark Matter ◽  
Globular Cluster ◽  
Particle Physics ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Density Profiles ◽  
Parallel Structures ◽  
Stellar Streams ◽  
Future Data ◽  
Low Mass

ABSTRACT The steepness of the central density profiles of dark matter (DM) in low-mass galaxy haloes (e.g. dwarf galaxies) is a powerful probe of the nature of DM. We propose a novel scheme to probe the inner profiles of galaxy subhaloes using stellar streams. We show that the present-day morphological and dynamical properties of accreted globular cluster (GC) streams – those produced from tidal stripping of GCs that initially evolved within satellite galaxies and later merged with the Milky Way (MW) – are sensitive to the central DM density profile and mass of their parent satellites. GCs that accrete within cuspy cold dark matter (CDM) subhaloes produce streams that are physically wider and dynamically hotter than streams that accrete inside cored subhaloes. A first comparison of MW streams ‘GD-1’ and ‘Jhelum’ (likely of accreted GC origin) with our simulations indicates a preference for cored subhaloes. If these results hold up in future data, the implication is that either the DM cusps were erased by baryonic feedback, or their subhaloes naturally possessed cored density profiles implying particle physics models beyond CDM. Moreover, accreted GC streams are highly structured and exhibit complex morphological features (e.g. parallel structures and ‘spurs’). This implies that the accretion scenario can naturally explain the recently observed peculiarities in some of the MW streams. We also propose a novel mechanism for forming ‘gaps’ in stellar streams when the remnant of the parent subhalo (which hosted the GC) later passes through the GC stream. This encounter can last a longer time (and have more of an impact) than the random encounters with DM subhaloes previously considered, because the GC stream and its parent subhalo are on similar orbits with small relative velocities. Current and future surveys of the MW halo will uncover numerous faint stellar streams and provide the data needed to substantiate our preliminary tests with this new probe of DM.

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