Hunting for Globular Clusters in the early universe

2019 ◽  
Vol 14 (S351) ◽  
pp. 212-215
Author(s):  
Frederika Phipps ◽  
Sadegh Khochfar ◽  
Anna Lisa Varri
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Globular Clusters ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Stellar Systems ◽  
Mass Relation ◽  
Cosmological Context ◽  
Low Mass ◽  
Stellar Density

AbstractSetting the formation of globular clusters (GCs) within a cosmological context and characterising the properties of proto-GCs at high redshift is currently a major challenge. In this work, we address that challenge by exploring a suit of high-resolution cosmological simulations from the First Billion Years (FiBY) project z at ⩾6 to investigate theoretical scenarios concerning the formation of old, low-mass stellar systems with a particular focus on GCs. Two distinct groups of objects are identified in the simulations. The first group of objects, with a high baryon fraction, we associate with proto-GCs. The second group, that exhibit a high stellar fraction, could be forming ultra-faint dwarf galaxies (UFDs). The objects with high baryon fraction are promising proto-GC candidates because they have little to no dark matter (DM), have number densities consistent with predictions from the literature, are very compact and have a high stellar density. We fit and also assess the redshift-zero globular system mass - halo mass relation and find it provides a reasonable fit to our proto-GC objects, indicating that this relation is likely set at formation.

The connection between the formation of galaxies and that of their central supermassive black holes

2005 ◽  
Vol 363 (1828) ◽  
pp. 705-713
Author(s):  
Martin G. Haehnelt
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Globular Clusters ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Host Galaxies ◽  
Massive Black Holes ◽  
Essential Ingredient ◽  
Open Questions ◽  
Very High

Massive black holes appear to be an essential ingredient of massive galactic bulges but little is known yet to what extent massive black holes reside in dwarf galaxies and globular clusters. Massive black holes most likely grow by a mixture of merging and accretion of gas in their hierarchically merging host galaxies. While the hierarchical merging of dark matter structures extends to sub-galactic scales and very high redshift, it is uncertain if the same is true for the build–up of massive black holes. I discuss here some of the relevant problems and open questions.

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 The systematically varying stellar IMF

2019 ◽  
Vol 14 (S351) ◽  
pp. 117-121 ◽  
Author(s):  
Pavel Kroupa
Keyword(s):  
Globular Clusters ◽  
Massive Star ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Star Formation Rate ◽  
High Redshift ◽  
Formation Rate ◽  
Low Mass Stars ◽  
Dynamical Mass ◽  
Low Mass

AbstractSome ultra-compact dwarf galaxies have large dynamical mass to light (M / L) ratios and also appear to contain an overabundance of LMXB sources, and some Milky Way globular clusters have a low concentration and appear to have a deficit of low-mass stars. These observations can be explained if the stellar IMF becomes increasingly top-heavy with decreasing metallicity and increasing gas density of the forming object. The thus constrained stellar IMF then accounts for the observed trend of metallicity and M / L ratio found amongst M31 globular star clusters. It also accounts for the overall shift of the observationally deduced galaxy-wide IMF from top-light to top-heavy with increasing star formation rate amongst galaxies. If the IMF varies similarly to deduced here, then extremely young very massive star-burst clusters observed at a high redshift would appear quasar-like (Jerabkova et al. 2017).

scholarly journals Dark matter-deficient dwarf galaxies form via tidal stripping of dark matter in interactions with massive companions

2021 ◽  
Vol 502 (2) ◽  
pp. 1785-1796
Author(s):  
R A Jackson ◽  
S Kaviraj ◽  
G Martin ◽  
J E G Devriendt ◽  
A Slyz ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Evolution ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Stellar Mass ◽  
Matter Content ◽  
Mass Relation ◽  
Potential Wells ◽  
Tidal Interactions ◽  
New Interactions

ABSTRACT In the standard ΛCDM (Lambda cold dark matter) paradigm, dwarf galaxies are expected to be dark matter-rich, as baryonic feedback is thought to quickly drive gas out of their shallow potential wells and quench star formation at early epochs. Recent observations of local dwarfs with extremely low dark matter content appear to contradict this picture, potentially bringing the validity of the standard model into question. We use NewHorizon, a high-resolution cosmological simulation, to demonstrate that sustained stripping of dark matter, in tidal interactions between a massive galaxy and a dwarf satellite, naturally produces dwarfs that are dark matter-deficient, even though their initial dark matter fractions are normal. The process of dark matter stripping is responsible for the large scatter in the halo-to-stellar mass relation in the dwarf regime. The degree of stripping is driven by the closeness of the orbit of the dwarf around its massive companion and, in extreme cases, produces dwarfs with halo-to-stellar mass ratios as low as unity, consistent with the findings of recent observational studies. ∼30 per cent of dwarfs show some deviation from normal dark matter fractions due to dark matter stripping, with 10 per cent showing high levels of dark matter deficiency (Mhalo/M⋆ < 10). Given their close orbits, a significant fraction of dark matter-deficient dwarfs merge with their massive companions (e.g. ∼70 per cent merge over time-scales of ∼3.5 Gyr), with the dark matter-deficient population being constantly replenished by new interactions between dwarfs and massive companions. The creation of these galaxies is therefore a natural by-product of galaxy evolution and their existence is not in tension with the standard paradigm.

scholarly journals Evidence of a population of dark subhaloes from Gaia and Pan-STARRS observations of the GD-1 stream

2021 ◽  
Vol 502 (2) ◽  
pp. 2364-2380
Author(s):  
Nilanjan Banik ◽  
Jo Bovy ◽  
Gianfranco Bertone ◽  
Denis Erkal ◽  
T J L de Boer
Keyword(s):  
Dark Matter ◽  
Mass Fraction ◽  
Molecular Clouds ◽  
Globular Clusters ◽  
Cold Dark Matter ◽  
Joint Analysis ◽  
Giant Molecular Clouds ◽  
Total Abundance ◽  
Hydrodynamical Simulation ◽  
Stellar Density

ABSTRACT New data from the Gaia satellite, when combined with accurate photometry from the Pan-STARRS survey, allow us to accurately estimate the properties of the GD-1 stream. Here, we analyse the stellar density variations in the GD-1 stream and show that they cannot be due to known baryonic structures such as giant molecular clouds, globular clusters, or the Milky Way’s bar or spiral arms. A joint analysis of the GD-1 and Pal 5 streams instead requires a population of dark substructures with masses ≈107–$10^9 \ \rm {M}_{\odot }$. We infer a total abundance of dark subhaloes normalized to standard cold dark matter $n_{\rm sub}/n_{\rm sub, CDM} = 0.4 ^{+0.3}_{-0.2}$ (68 per cent), which corresponds to a mass fraction contained in the subhaloes $f_{\rm {sub}} = 0.14 ^{+0.11}_{-0.07} {{\ \rm per\ cent}}$, compatible with the predictions of hydrodynamical simulation of cold dark matter with baryons.

scholarly journals Formation of massive globular clusters with dark matter and its implication on dark matter annihilation

2020 ◽  
Vol 496 (1) ◽  
pp. L70-L74
Author(s):  
Henriette Wirth ◽  
Kenji Bekki ◽  
Kohei Hayashi
Keyword(s):  
Dark Matter ◽  
Observational Studies ◽  
Globular Clusters ◽  
Galactic Halo ◽  
Dwarf Galaxies ◽  
Large Range ◽  
Dark Matter Annihilation ◽  
Central Regions ◽  
Γ Ray ◽  
The Masses

ABSTRACT Recent observational studies of γ-ray emission from massive globular clusters (GCs) have revealed possible evidence of dark matter (DM) annihilation within GCs. It is, however, still controversial whether the emission comes from DM or from millisecond pulsars. We here present the new results of numerical simulations, which demonstrate that GCs with DM can originate from nucleated dwarfs orbiting the ancient Milky Way. The simulated stripped nuclei (i.e. GCs) have the central DM densities ranging from 0.1 to several M⊙ pc−3, depending on the orbits and the masses of the host dwarf galaxies. However, GCs born outside the central regions of their hosts can have no/little DM after their hosts are destroyed and the GCs become the Galactic halo GCs. These results suggest that only GCs originating from stellar nuclei of dwarfs can possibly have DM. We further calculate the expected γ-ray emission from these simulated GCs and compare them to observations of ω Cen. Given the large range of DM densities in the simulated GCs, we suggest that the recent possible detection of DM annihilation from GCs should be more carefully interpreted.

scholarly journals The formation of ultradiffuse galaxies in the RomulusC galaxy cluster simulation

2020 ◽  
Vol 497 (3) ◽  
pp. 2786-2810 ◽  
Author(s):  
M Tremmel ◽  
A C Wright ◽  
A M Brooks ◽  
F Munshi ◽  
D Nagai ◽  
...  
Keyword(s):  
Dark Matter ◽  
Stellar Evolution ◽  
Dwarf Galaxies ◽  
Galaxy Cluster ◽  
High Mass ◽  
Tidal Interactions ◽  
Low Surface Brightness ◽  
Low Mass ◽  
Tidal Heating ◽  
Low Surface Brightness Galaxies

ABSTRACT We study the origins of 122 ultradiffuse galaxies (UDGs) in the Romulus c zoom-in cosmological simulation of a galaxy cluster (M200 = 1.15 × 1014 M⊙), one of the only such simulations capable of resolving the evolution and structure of dwarf galaxies (M⋆ < 109 M⊙). We find broad agreement with observed cluster UDGs and predict that they are not separate from the overall cluster dwarf population. UDGs in cluster environments form primarily from dwarf galaxies that experienced early cluster in-fall and subsequent quenching due to ram pressure. The ensuing dimming of these dwarf galaxies due to passive stellar evolution results in a population of very low surface brightness galaxies that are otherwise typical dwarfs. UDGs and non-UDGs alike are affected by tidal interactions with the cluster potential. Tidal stripping of dark matter, as well as mass-loss from stellar evolution, results in the adiabatic expansion of stars, particularly in the lowest mass dwarfs. High-mass dwarf galaxies show signatures of tidal heating while low-mass dwarfs that survive until z = 0 typically have not experienced such impulsive interactions. There is little difference between UDGs and non-UDGs in terms of their dark matter haloes, stellar morphology, colours, and location within the cluster. In most respects cluster UDG and non-UDGs alike are similar to isolated dwarf galaxies, except for the fact that they are typically quenched.

scholarly journals Testing for Dark Matter in the Outskirts of Globular Clusters

2021 ◽  
Vol 922 (2) ◽  
pp. 104
Author(s):  
Raymond G. Carlberg ◽  
Carl J. Grillmair
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
High Probability ◽  
Velocity Dispersion ◽  
High Redshift ◽  
Dark Matter Halo ◽  
The Sun ◽  
Proper Motions ◽  
Preliminary Results ◽  
Galactic Background

Abstract The proper motions of stars in the outskirts of globular clusters are used to estimate cluster velocity dispersion profiles as far as possible within their tidal radii. We use individual color–magnitude diagrams to select high-probability cluster stars for 25 metal-poor globular clusters within 20 kpc of the Sun, 19 of which have substantial numbers of stars at large radii. Of the 19, 11 clusters have a falling velocity dispersion in the 3–6 half-mass radii range, 6 are flat, and 2 plausibly have a rising velocity dispersion. The profiles are all in the range expected from simulated clusters that started at high redshift in a zoom-in cosmological simulation. The 11 clusters with falling velocity dispersion profiles are consistent with no dark matter above the Galactic background. The six clusters with approximately flat velocity dispersion profiles could have local dark matter, but are ambiguous. The two clusters with rising velocity dispersion profiles are consistent with a remnant local dark matter halo, but need membership confirmation and detailed orbital modeling to further test these preliminary results.

scholarly journals Dark Matter in Dwarf Galaxies: High Resolution Observations

2004 ◽  
Vol 220 ◽  
pp. 353-358 ◽  
Author(s):  
Alberto D. Bolatto ◽  
Joshua D. Simon ◽  
Adam Leroy ◽  
Leo Blitz
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Rotation Curve ◽  
Dwarf Galaxies ◽  
Full Range ◽  
Dark Matter Halo ◽  
Central Density ◽  
Constant Density ◽  
Density Profiles ◽  
Central Regions

We present observations and analysis of rotation curves and dark matter halo density profiles in the central regions of four nearby dwarf galaxies. This observing program has been designed to overcome some of the limitations of other rotation curve studies that rely mostly on longslit spectra. We find that these objects exhibit the full range of central density profiles between ρ ∝ r0 (constant density) and ρ ∝ r–1 (NFW halo). This result suggests that there is a distribution of central density slopes rather than a unique halo density profile.

scholarly journals Study of gravitational fields and globular cluster systems of early-type galaxies

2019 ◽  
Vol 625 ◽  
pp. A32 ◽  
Author(s):  
M. Bílek ◽  
S. Samurović ◽  
F. Renaud
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Globular Clusters ◽  
Mass Relation ◽  
Early Type ◽  
Radial Acceleration ◽  
Galaxy Interactions ◽  
Gravitational Fields ◽  
Stellar Masses ◽  
Best Fit

Context.Gravitational fields at the outskirts of early-type galaxies (ETGs) are difficult to constrain observationally. It thus remains poorly explored how well the ΛCDM and MOND hypotheses agree with ETGs.Aims.The dearth of studies on this topic motivated us to gather a large sample of ETGs and examine homogeneously which dark matter halos they occupy, whether the halos follow the theoretically predicted stellar-to-halo mass relation (SHMR) and the halo mass-concentration relation (HMCR), whether ETGs obey MOND and the radial acceleration relation (RAR) observed for late-type galaxies (LTGs), and finally whether ΛCDM or MOND perform better in ETGs.Methods.We employed Jeans analysis of radial velocities of globular clusters (GCs). We analysed nearly all ETGs having more than about 100 archival GC radial velocity measurements available. The GC systems of our 17 ETGs extend mostly over ten effective radii. A ΛCDM simulation of GC formation helped us to interpret the results.Results.Successful ΛCDM fits are found for all galaxies, but compared to the theoretical HMCR and SHMR, the best-fit halos usually have concentrations that are too low and stellar masses that are too high for their masses. This might be because of tidal stripping of the halos or because ETGs and LTGs occupy different halos. Most galaxies can be fitted by the MOND models successfully as well, but for some of the galaxies, especially those in centers of galaxy clusters, the observed GC velocity dispersions are too high. This might be a manifestation of the additional dark matter that MOND requires in galaxy clusters. Additionally, we find many signs that the GC systems were perturbed by galaxy interactions. Formal statistical criteria prefer the best-fit ΛCDM models over the MOND models, but this might be due to the higher flexibility of the ΛCDM models. The MOND approach can predict the GC velocity dispersion profiles better.

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