The number of globular clusters around the iconic UDG DF44 is as expected for dwarf galaxies

Abstract There is a growing consensus that the vast majority of ultra-diffuse galaxies (UDGs) are dwarf galaxies. However, there remain a few UDGs that seem to be special in terms of their globular cluster (GC) systems. In particular, according to some authors, certain UDGs exhibit large GC populations when compared to expectations from their stellar (or total) mass. Among these special UDGs, DF44 in the Coma cluster is one of the better-known examples. DF44 has been claimed to have a relatively high number of GCs, $N_{GC}=74^{+18}_{-18}$, for a stellar mass of only 3 × 108M⊙ which would indicate a much larger dark halo mass than dwarfs of similar stellar mass. In this paper we revisit this number and, contrary to previous results, find $N_{GC}=21^{+7}_{-9}$ assuming that the distribution of the GCs follows the same geometry as the galaxy. If we assume that the GCs around DF44 are distributed in a (projected) circularly symmetric way and, if we use a less strict criterion for the selection of the GCs, we find $N_{GC}=18^{+23}_{-12}$. Making use of the MGC − Mhalo relation, this number of GCs suggests a dark matter halo mass of $M_{halo}=1.1^{+0.4}_{-0.5} \times 10^{11} M_{\odot }$, a value which is consistent with the expected total mass for DF44 based on its velocity dispersion, $\sigma =33^{+3}_{-3}$ km s−1. We conclude that the number of GCs around DF44 is as expected for regular dwarf galaxies of similar stellar mass and DF44 is not extraordinary in this respect.

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LMC Clusters: Young

Symposium - International Astronomical Union ◽

10.1017/s0074180900092056 ◽

1980 ◽

Vol 85 ◽

pp. 317-323 ◽

Cited By ~ 1

Author(s):

K. C. Freeman

Keyword(s):

Chemical Composition ◽

Age Structure ◽

Total Mass ◽

Globular Clusters ◽

Massive Stars ◽

Mass Range ◽

Stellar Mass ◽

Stellar Content ◽

The Galaxy ◽

Mass Functions

The young globular clusters of the LMC have ages of 107–108 y. Their masses and structure are similar to those of the smaller galactic globular clusters. Their stellar mass functions (in the mass range 6 m⊙ to 1.2 m⊙) vary greatly from cluster to cluster, although the clusters are similar in total mass, age, structure and chemical composition. It would be very interesting to know why these clusters are forming now in the LMC and not in the Galaxy.I will talk about the “young globular” or “blue populous” clusters of the LMC. They were first identified as a family by Hodge (1961). The ages of these objects are 107 to 108 y, and their masses are 104 to 105 m⊙, so they are populous enough to be really useful for studying the evolution of massive stars. I will not discuss this aspect (see the extensive work by Flower and Hodge and Robertson since 1974), but will concentrate on the structure and stellar content of these young clusters.

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Globular clusters in Coma cluster ultra-diffuse galaxies (UDGs): evidence for two types of UDG?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa180 ◽

2020 ◽

Vol 492 (4) ◽

pp. 4874-4883 ◽

Cited By ~ 9

Author(s):

Duncan A Forbes ◽

Adebusola Alabi ◽

Aaron J Romanowsky ◽

Jean P Brodie ◽

Nobuo Arimoto

Keyword(s):

Globular Clusters ◽

Surface Brightness ◽

Dwarf Galaxies ◽

Hubble Space Telescope ◽

Stellar Populations ◽

Stellar Mass ◽

Host Galaxy ◽

Mass Relation ◽

Stellar Content ◽

Coma Cluster

ABSTRACT Ultra-diffuse galaxies (UDGs) reveal extreme properties. Here, we compile the largest study to date of 85 globular cluster (GC) systems around UDGs in the Coma cluster, using new deep ground-based imaging of the known UDGs and existing imaging from the Hubble Space Telescope of their GC systems. We find that the richness of GC systems in UDGs generally exceeds that found in normal dwarf galaxies of the same stellar mass. These GC-rich UDGs imply haloes more massive than expected from the standard stellar mass–halo mass relation. The presence of such overly massive haloes presents a significant challenge to the latest simulations of UDGs in cluster environments. In some exceptional cases, the mass in the GC system is a significant fraction of the stellar content of the host galaxy. We find that rich GC systems tend to be hosted in UDGs of lower luminosity, smaller size, and fainter surface brightness. Similar trends are seen for normal dwarf galaxies in the Coma cluster. A toy model is presented in which the GC-rich UDGs are assumed to be ‘failed’ galaxies within massive haloes that have largely old, metal-poor, alpha-element-enhanced stellar populations. On the other hand, GC-poor UDGs are more akin to normal, low surface brightness dwarfs that occupy less massive dark matter haloes. Additional data on the stellar populations of UDGs with GC systems will help to further refine and test this simplistic model.

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2dF Spectroscopy of Globular Clusters in M104

Highlights of Astronomy ◽

10.1017/s1539299600015653 ◽

2005 ◽

Vol 13 ◽

pp. 199-199

Author(s):

Terry Bridges ◽

Steve Zepf ◽

Katherine Rhode ◽

Ken Freeman

Keyword(s):

Dark Matter ◽

Strong Evidence ◽

Total Mass ◽

Globular Clusters ◽

Total Sample ◽

Dark Matter Halo ◽

Large Radius ◽

Counter Rotation ◽

Spatial Coverage

AbstractWe have found 56 new globular clusters in M104 from 2dF multi-fiber spectroscopy, doubling the number of confirmed clusters, and extending the spatial coverage to 50 kpc radius. We find no significant rotation in the total sample, or for subsets split by color or radius. However, there are hints that the blue clusters have a higher rotation than the red clusters, and for counter-rotation of clusters at large radius. We find a total mass of M ~ 1 × 1012M⊙ and a (M/L)B =30 out to 50 kpc radius, which is strong evidence for a dark matter halo in M104.

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About the Coma Cluster (Progress Report)

Symposium - International Astronomical Union ◽

10.1017/s0074180900149988 ◽

1987 ◽

Vol 117 ◽

pp. 112-112

Author(s):

D. Gerbal ◽

G. Mathez ◽

A. Mazure ◽

E. Salvadore-Solé

Keyword(s):

Total Mass ◽

Velocity Dispersion ◽

Dynamical Evolution ◽

Dynamical Analysis ◽

Radial Dependence ◽

Cluster Center ◽

Coma Cluster ◽

Massive Galaxies ◽

Relaxation Effects ◽

The Galaxy

The study of the dynamics of the Coma Cluster is of interest for several reasons. First, there exists a great deal of observational information about the cluster, including data on morphology, magnitude, color and redshift for the galaxies, and reasonably detailed x-ray data for the hot gas. Second, the present dynamical state of the cluster is reasonably well-defined. In addition, the segregation of the more luminous (≡ massive) galaxies towards the cluster center shows that two-body relaxation effects are well-advanced (Capelato et al. 1980). The profile of velocity dispersion with radius shows that in the outer parts of the cluster the galaxy velocities are non-isothermal (des Forêts et al. 1984). There is, however, evidence of continuing dynamical evolution. The velocity field of the galaxies at large distances from the center of the cluster suggests continuing infall (Capelato et al. 1982), and two sub-condensations are located in the inner regions (Mazure and Proust 1986). A new dynamical analysis for the cluster is being carried out in two stages. First, a relaxed model with a wide mass spectrum (c.f. Inagaki 1980) is fitted to the data. The contribution of the intergalactic gas is taken into account. With HO = 75 km/sec/Mpc, the total mass within a 3° radius of the center is ∼ 1.5 × 1015 M⊙, of which ∼ 30% is in the intergalactic medium, and M/L ∼ 75 M⊙/L⊙. The ratio of specific energies of the galaxies and the gas is ∼ 1.1, i.e., there is no scale-height problem (these results are described more fully by Gerbal et al. 1986). A second “model independent” analysis using the profiles of the galactic density and velocity dispersion gives the radial dependence of the galactic mass, the gas mass and also gives the total mass, which is found to be ∼ 1.1 × 1015 M⊙ within 3° (Gerbal et al. 1984).

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The Dark Halo – Spheroid Conspiracy

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313004808 ◽

2012 ◽

Vol 8 (S295) ◽

pp. 208-208

Author(s):

Rhea-Silvia Remus ◽

Andreas Burkert ◽

Klaus Dolag ◽

Peter H. Johansson ◽

Thorsten Naab ◽

...

Keyword(s):

Elliptical Galaxies ◽

Total Density ◽

Dark Halo ◽

Coma Cluster ◽

Density Profiles ◽

Stellar Component ◽

Strong Lensing ◽

The Galaxy ◽

Good Agreement

AbstractObservational results from strong lensing and dynamical modeling indicate that the total density profiles of early-type galaxies are close to isothermal, i.e. ρtot ∝ rγ with γ ≈ −2. To understand the origin of this universal slope we study a set of simulated spheroids formed in cosmological hydrodynamical zoom-in simulations (see Oser et al. 2010 for more details). We find that the total stellar plus dark matter density profiles of all our simulations on average can be described by a power law with a slope of γ ≈ −2.1, with a tendency towards steeper slopes for more compact, lower mass ellipticals, while the total intrinsic velocity dispersion is flat for all simulations, independent of the values of γ. Our results are in good agreement with observations of Coma cluster ellipticals (Thomas et al. 2007) and results from strong lensing (Sonnenfeld et al. 2012). We find that for z ≳ 2 the majority of the stellar build-up occurs through in-situ star formation, i.e. the gas falls to the center of the galaxy and forms stars, causing the galaxy to be more compact and thus the stellar component to be more dominant. As a result, the total density slopes at z ≈ 2 are generally steeper (around γ ≈ −3). Between z = 2 and z = 0 galaxies grow mostly through dry merging, with each merging event shifting the slope more towards γ ≈ −2. We conclude from our simulations that the steepness of the slope of present day galaxies is a signature of the importance of mostly dry mergers in the formation of an elliptical, and suggest that all elliptical galaxies will with time end up in a configuration with a density slope of γ ≈ −2. For a more detailed analysis with a larger sample of simulations see Remus et al. (2013).

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Galaxy and mass assembly: luminosity and stellar mass functions in GAMA groups

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2889 ◽

2020 ◽

Vol 499 (1) ◽

pp. 631-652

Author(s):

J A Vázquez-Mata ◽

J Loveday ◽

S D Riggs ◽

I K Baldry ◽

L J M Davies ◽

...

Keyword(s):

Star Formation ◽

Formation Rate ◽

Mass Function ◽

Stellar Mass ◽

Dark Matter Halo ◽

Central Mass ◽

The Galaxy ◽

Star Formation In Galaxies ◽

Low Mass ◽

Mass Assembly

ABSTRACT How do galaxy properties (such as stellar mass, luminosity, star formation rate, and morphology) and their evolution depend on the mass of their host dark matter halo? Using the Galaxy and Mass Assembly group catalogue, we address this question by exploring the dependence on host halo mass of the luminosity function (LF) and stellar mass function (SMF) for grouped galaxies subdivided by colour, morphology, and central/satellite. We find that spheroidal galaxies in particular dominate the bright and massive ends of the LF and SMF, respectively. More massive haloes host more massive and more luminous central galaxies. The satellites LF and SMF, respectively, show a systematic brightening of characteristic magnitude, and increase in characteristic mass, with increasing halo mass. In contrast to some previous results, the faint-end and low-mass slopes show little systematic dependence on halo mass. Semi-analytic models and simulations show similar or enhanced dependence of central mass and luminosity on halo mass. Faint and low-mass simulated satellite galaxies are remarkably independent of halo mass, but the most massive satellites are more common in more massive groups. In the first investigation of low-redshift LF and SMF evolution in group environments, we find that the red/blue ratio of galaxies in groups has increased since redshift z ≈ 0.3 relative to the field population. This observation strongly suggests that quenching of star formation in galaxies as they are accreted into galaxy groups is a significant and ongoing process.

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Short Period Variables in the Magellanic Cloud Cluster NGC 1466

International Astronomical Union Colloquium ◽

10.1017/s025292110003342x ◽

1973 ◽

Vol 21 ◽

pp. 113-119 ◽

Cited By ~ 1

Author(s):

M. V. Norris

Keyword(s):

Globular Cluster ◽

Metal Content ◽

Globular Clusters ◽

Magellanic Clouds ◽

Horizontal Branch ◽

A Value ◽

Short Period ◽

Magnitude Diagram ◽

The Galaxy ◽

Metal Abundance

NGC 1466 (α1950 = 3h44.m6, δ1950= -71°45’) is a globular cluster which appears to be situated between the two Magellanic Clouds. Previous estimates (Gascoigne, 1966) put it at roughly the same distance from us as the LMC, so it is regarded as a member of the Cloud system. It is globular in appearance, and its colour-magnitude diagram confirms this classification. It has a fairly well-developed horizontal branch, and was found by Wesselink (1970) to be quite rich in variables. The metallicity index, Q, (van den Bergh, 1967) has a value of -0.36 for NGC 1466 (Andrews and Lloyd Evans, 1971). This would rank it with M5 and NGC 6171 as a cluster of intermediate metal content. This comparison is consistent with the value of Δ V for the cluster, which, at 2.m6, is representative of the Δ V values of globular clusters of intermediate metal abundance in the Galaxy.

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Dwarf Galaxies and Cluster Environments

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318006890 ◽

2018 ◽

Vol 14 (S344) ◽

pp. 373-376

Author(s):

Yasuhiro Hashimoto ◽

J. Patrick Henry ◽

Hans Böhringer

Keyword(s):

Dwarf Galaxies ◽

Dwarf Galaxy ◽

Detection Algorithm ◽

Diffuse Light ◽

X Ray ◽

Optical Images ◽

Highly Sensitive ◽

The Galaxy ◽

Galaxy Populations ◽

Selection Of

AbstractWe report an investigation of the properties of dwarf galaxies (Mr < -15) inside 26 clusters at z = 0.15 – 0.25, using the X-ray data from the Chandra archive, and optical images taken with Subaru Suprime-Cam. Our results include: 1. Investigation of the dwarf galaxy density distribution is sensitive to the background galaxies and the choice of colour selection of galaxies. 2. Cluster-centric dwarf-to-giant ratio is highly sensitive to the level of subtracted background galaxies. 3. A certain fraction of faint galaxies always remain undetected by the detection algorithm near the center of clusters, even after carefully treating the halo or extra diffuse light created by bright galaxies. The number of ‘undetected’ faint galaxies varies significantly from cluster to cluster, and even from pointing to pointing. 4. Dwarf galaxies extend up to 2 Mpc from the center in most clusters. Meanwhile, the distribution of blue dwarf galaxies extends more to the outside. 5. For a given colour, the spatial distributions of dwarf galaxies and giant galaxies become similar. Namely, the most of the radial distribution comes from the colour, rather than the size, of galaxies. 6. Relative to the NFW profile, all of the galaxy populations are showing a deficit near the cluster core (r < 0.3 Mpc). 7. The dwarf-to-giant ratio shows no variation against cluster measures such as the richness and X-ray luminosity, as well as various cluster X-ray characteristics related to possible dynamical status of clusters.

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Formation of globular clusters with multiple stellar populations from massive gas clumps in high-z gas-rich dwarf galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201629898 ◽

2019 ◽

Vol 622 ◽

pp. A53 ◽

Cited By ~ 8

Author(s):

K. Bekki

Keyword(s):

Mass Fraction ◽

Total Mass ◽

Globular Clusters ◽

Dwarf Galaxies ◽

Stellar System ◽

Stellar Populations ◽

Stellar Systems ◽

Agb Stars ◽

Time Step ◽

Gas Accretion

Context. One of the currently favored scenarios for the formation of globular clusters (GCs) with multiple stellar populations is that an initial massive stellar system forms (“first generation”, FG), subsequently giving rise to gaseous ejecta which is converted into a second-generation (SG) of stars to form a GC. How such GCs with such FG and SG populations form and evolve, however, remains unclear. Aims. We therefore investigate, for the first time, the sequential formation processes of both FG and SG stars from star-forming massive gas clumps in gas-rich dwarf disk galaxies. Methods. We adopt a novel approach to resolve the two-stage formation of GCs in hydrodynamical simulations of dwarf galaxies. In the new simulations, new gas particles that are much less massive than their parent star particle are generated around each new star particle when the new star enters into the asymptotic giant branch (AGB) phase. Furthermore, much finer maximum time step width (~105 yr) and smaller softening length (~2 pc) are adopted for such AGB gas particles to properly resolve the ejection of gas from AGB stars and AGB feedback effects. Therefore, secondary star formation from AGB ejecta can be properly investigated in galaxy-scale simulations. Results. An FG stellar system can first form from a massive gas clump developing due to gravitational instability within its host gas-rich dwarf galaxy. Initially the FG stellar system is not a single massive cluster, but instead is composed of several irregular stellar clumps (or filaments) with a total mass larger than 106 M⊙. While the FG system is dynamically relaxing, gaseous ejecta from AGB stars can be gravitationally trapped by the FG system and subsequently converted into new stars to form a compact SG stellar system within the FG system. Interestingly, about 40% of AGB ejecta is from stars that do not belong to the FG system (“external gas accretion”). FG and SG stellar systems have different amplitudes of internal rotation and V∕σ. The mass-density (MSG−ρSG) relation for SG stellar systems can be approximated as ρSG ∝ MSG1.5. There can be a threshold total mass of GC host galaxies (Mth = [5 − 23] × 109 M⊙) beyond which the formation of GCs with compact SG stellar systems is possible. Both the initial baryonic mass fraction and the gas mass fraction in dwarfs are crucial parameters that determine whether or not GCs can contain multiple stellar populations. GCs with compact SG stellar systems are more likely to form in dwarf disks with larger gas mass fractions and higher surface mass densities. Formation of binary GCs with SGs and the subsequent GC merging are clearly seen in some models. The derived external gas-accretion process in FG systems initially consisting of stellar clumps will need to be investigated further in more sophisticated simulations.

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A systematic search for galaxy proto-cluster cores at z ∼ 2

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1757 ◽

2020 ◽

Vol 496 (3) ◽

pp. 3169-3181

Author(s):

Makoto Ando ◽

Kazuhiro Shimasaku ◽

Rieko Momose

Keyword(s):

Galaxy Formation ◽

Mass Range ◽

Mass Function ◽

Stellar Mass ◽

Dark Matter Halo ◽

Massive Galaxies ◽

Quenching Efficiency ◽

The Galaxy ◽

Mass Assembly ◽

Cluster Cores

ABSTRACT A proto-cluster core is the most massive dark matter halo (DMH) in a given proto-cluster. To reveal the galaxy formation in core regions, we search for proto-cluster cores at z ∼ 2 in ${\sim}1.5\, \mathrm{deg}^{2}$ of the COSMOS field. Using pairs of massive galaxies [log (M*/M⊙) ≥ 11] as tracers of cores, we find 75 candidate cores, among which 54 per cent are estimated to be real. A clustering analysis finds that these cores have an average DMH mass of $2.6_{-0.8}^{+0.9}\times 10^{13}\, \mathrm{M}_{\odot }$, or $4.0_{-1.5}^{+1.8}\, \times 10^{13} \, \mathrm{M}_{\odot }$ after contamination correction. The extended Press–Schechter model shows that their descendant mass at z = 0 is consistent with Fornax-like or Virgo-like clusters. Moreover, using the IllustrisTNG simulation, we confirm that pairs of massive galaxies are good tracers of DMHs massive enough to be regarded as proto-cluster cores. We then derive the stellar mass function (SMF) and the quiescent fraction for member galaxies of the 75 candidate cores. We find that the core galaxies have a more top-heavy SMF than field galaxies at the same redshift, showing an excess at log (M*/M⊙) ≳ 10.5. The quiescent fraction, $0.17_{-0.04}^{+0.04}$ in the mass range 9.0 ≤ log (M*/M⊙) ≤ 11.0, is about three times higher than that of field counterparts, giving an environmental quenching efficiency of $0.13_{-0.04}^{+0.04}$. These results suggest that stellar mass assembly and quenching are accelerated as early as z ∼ 2 in proto-cluster cores.

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