Constraints on Galaxy Formation from Extragalactic Globular Clusters

The merger model for elliptical galaxy formation has received increasing attention since it was first suggested by Toomre & Toomre (1972). Van den Bergh (1984) pointed out a problem with the idea that elliptical galaxies were formed by simply combining two, or more, spiral galaxies. He noted that the specific frequency (SN, number of globular clusters per unit galaxy light) is systematically lower for spirals than for ellipticals. Schweizer (1987) suggested that globular clusters (GCs) might be expected to form in the merger process, thereby alleviating or possibly eliminating the SN problem. Ashman & Zepf (1992) developed this idea into a merger model for GC formation with testable predictions. We recently examined this model in the light of new HST and ground-based imaging data on the blue and red sub-populations of GCs in elliptical galaxies (Forbes, Brodie & Grillmair 1997). We concluded that the merger model for GC formation has serious problems, particularly in explaining the characteristics of GCs in giant elliptical galaxies with high SN. A multi-phase collapse scenario was suggested as more consistent with the available evidence.

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Globular Clusters as Probes of the Formation History of Elliptical Galaxies: Results for NGC 4472

Symposium - International Astronomical Union ◽

10.1017/s0074180900223991 ◽

2002 ◽

Vol 207 ◽

pp. 333-335

Author(s):

K.L. Rhode ◽

S.E. Zepf

Keyword(s):

Galaxy Formation ◽

Globular Cluster ◽

Globular Clusters ◽

Spiral Galaxies ◽

Elliptical Galaxy ◽

Elliptical Galaxies ◽

Cluster Systems ◽

Large Sample ◽

Formation History ◽

History Of

We have undertaken a survey of the globular cluster systems of a large sample of elliptical and spiral galaxies in order to test predictions of elliptical galaxy formation models. Here we outline the survey and present a summary of our results for the Virgo elliptical NGC 4472.

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The Formation and Evolution of Star Clusters and Galaxies

Highlights of Astronomy ◽

10.1017/s1539299600015938 ◽

2005 ◽

Vol 13 ◽

pp. 347-349

Author(s):

Stephen E. Zepf

Keyword(s):

Galaxy Formation ◽

Globular Cluster ◽

Globular Clusters ◽

Near Infrared ◽

Cluster Formation ◽

Star Clusters ◽

Elliptical Galaxies ◽

Cluster Systems ◽

Important Observation ◽

Formation And Evolution

AbstractThis paper addresses the questions of what we have learned about how and when dense star clusters form, and what studies of star clusters have revealed about galaxy formation and evolution. One important observation is that globular clusters are observed to form in galaxy mergers and starbursts in the local universe, which both provides constraints on models of globular cluster formation, and suggests that similar physical conditions existed when most early-type galaxies and their globular clusters formed in the past. A second important observation is that globular cluster systems typically have bimodal color distributions. This was predicted by merger models, and indicates an episodic formation history for elliptical galaxies. A third and very recent result is the discovery of large populations of intermediate age globular clusters in several elliptical galaxies through the use of optical to near-infrared colors. These provide an important link between young cluster systems observed in starbursts and mergers and old cluster systems. This continuum of ages of the metal-rich globular cluster systems also indicates that there is no special age or epoch for the formation of the metal-rich globular clusters, which comprise about half of the cluster population. The paper concludes with a brief discussion of recent results on the globular cluster – low-mass X-ray binary connection.

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Globular Cluster Systems of Elliptical Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900112483 ◽

1999 ◽

Vol 186 ◽

pp. 173-180

Author(s):

Stephen E. Zepf ◽

Keith M. Ashman

Keyword(s):

Galaxy Formation ◽

Globular Cluster ◽

Globular Clusters ◽

Spiral Galaxies ◽

Elliptical Galaxies ◽

Cluster Systems ◽

Physical Mechanisms ◽

Cd Galaxies ◽

Simplifying Assumptions ◽

Poor Population

We review the observed properties of globular cluster systems and their implications for models of galaxy formation. Observations show that globular clusters form in gas-rich mergers, and that bimodal metallicity distributions are common in the globular cluster systems of ellipticals, with the metal-poor population more extended than the metal-rich one. These are three of the four predictions of the simple merger model of Ashman & Zepf (1992). The fourth prediction concerns the properties of the globular cluster systems of spirals, and is still to be tested by observation. Adopting Occam's razor, the confirmation of the fundamental predictions of the merger model from both young and old globular cluster systems is strong evidence that typical elliptical galaxies formed from the mergers of spiral galaxies. However, the simplifying assumptions of the Ashman-Zepf merger model limit its applicability to certain complex situations such as the formation of cD galaxies. We conclude this review by introducing new observational and theoretical programs that will further the understanding of the physical mechanisms of globular cluster and galaxy formation.

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Proto–Globular Cluster Candidates in NGC 1275

Symposium - International Astronomical Union ◽

10.1017/s0074180900112744 ◽

1999 ◽

Vol 186 ◽

pp. 273-274

Author(s):

Jean P. Brodie

Keyword(s):

Globular Cluster ◽

Spiral Galaxies ◽

Cluster Formation ◽

Elliptical Galaxies ◽

Cooling Flows ◽

Ngc 1275 ◽

Perseus Cluster ◽

Important Test

The discovery, with HST imaging, of proto–globular cluster candidates in NGC 1275 (Holtzman et al. 1992) was regarded by many as a major success of the merger model for globular cluster formation (e.g. Ashman & Zepf 1992) and has been cited in support of the idea that elliptical galaxies form from the merger of two or more spiral galaxies. A prediction of the Ashman & Zepf model was that newly-formed clusters should be observable in currently or recently merging systems. The NGC 1275 clusters constitute an important test of globular cluster formation models. NGC 1275 is the peculiar cD galaxy at the center of the Perseus cluster. It shows evidence for a merger history and may indeed be undergoing a merger at present. It also has one of the largest known cooling flows.

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Measuring the GC luminosity function up to z ~ 0.2

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309991256 ◽

2009 ◽

Vol 5 (S266) ◽

pp. 351-351

Author(s):

K. A. Alamo-Martínez ◽

R. A. González-Lópezlira ◽

J. Blakeslee

Keyword(s):

Galaxy Formation ◽

Globular Clusters ◽

Surface Brightness ◽

Luminosity Function ◽

Elliptical Galaxy ◽

Angular Size ◽

Spectroscopic Studies ◽

Stellar Systems ◽

Surface Brightness Fluctuations ◽

Specific Frequency

AbstractGlobular clusters (GCs) are stellar systems (~106 M⊙) with very regular symmetry, single age, and single metallicity. Spectroscopic studies have revealed very old ages, suggesting that GCs were formed in the earliest stages of galaxy formation and assembly. The aim of this work is to find out how far we can measure the GC luminosity function, specific frequency, and radial distribution, applying the surface-brightness-fluctuations (SBF) technique to deep ACS images. To this end, we apply the effects caused by higher redshift to HST/ACS images (in two optical bands, F606W and F814W) of M87, an elliptical galaxy with a very well-studied GC system. The effects involved are: (i) evolution, (ii) inverse k correction, (iii) binning of the image to smaller angular size, (iv) cosmological dimming of surface brightness, and (v) noise addition to account for different exposure times. After processing the images we detect the brightest GCs through direct photometry (e.g., with SExtractor), whereas the unresolved clusters are measured through SBFs. The above treatment is repeated for z=0.05, 0.1, 0.14, and 0.18, and the results are compared to the measurements at z=0 to estimate biases and incompleteness.

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Modeling Formation of Globular Clusters: Beacons of Galactic Star Formation

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311000676 ◽

2010 ◽

Vol 6 (S270) ◽

pp. 381-384

Author(s):

Oleg Y. Gnedin

Keyword(s):

Star Formation ◽

Galaxy Formation ◽

Globular Cluster ◽

Globular Clusters ◽

Cluster Formation ◽

Star Clusters ◽

Mass Function ◽

Giant Molecular Clouds ◽

Early Galaxies ◽

The Masses

AbstractModern hydrodynamic simulations of galaxy formation are able to predict accurately the rates and locations of the assembly of giant molecular clouds in early galaxies. These clouds could host star clusters with the masses and sizes of real globular clusters. I describe current state-of-the-art simulations aimed at understanding the origin of the cluster mass function and metallicity distribution. Metallicity bimodality of globular cluster systems appears to be a natural outcome of hierarchical formation and gradually declining fraction of cold gas in galaxies. Globular cluster formation was most prominent at redshifts z > 3, when massive star clusters may have contributed as much as 20% of all galactic star formation.

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Witnessing globular cluster formation at z ∼ 3–10 with JWST and ELT

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319008846 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 33-37

Author(s):

Alvio Renzini

Keyword(s):

Galaxy Formation ◽

Globular Cluster ◽

Globular Clusters ◽

Cluster Formation ◽

Early Stages

AbstractThe opportunities offered by JWST and the ELT for the detection and study of forming/just formed globular clusters at high redshifts are illustrated, also alluding at the unique insight we may get on the very early stages of galaxy formation.

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Star Clusters as Touchstones for Theories of Galactic Evolution — A Few Examples

Symposium - International Astronomical Union ◽

10.1017/s0074180900091592 ◽

1980 ◽

Vol 85 ◽

pp. 1-12

Author(s):

Sidney van den Bergh

Keyword(s):

Globular Clusters ◽

Supernova Remnant ◽

Elliptical Galaxy ◽

Cluster Formation ◽

Elliptical Galaxies ◽

Blue Stragglers ◽

Tidal Forces ◽

Physical Environments ◽

Distant Galaxies ◽

Irregular Galaxies

Observations of NGC 5128 (Cen A) show that this giant elliptical galaxy contains few globular clusters. The fact that the number of globular clusters per unit luminosity in E galaxies has a range of ∼ 102 indicates that different ellipticals were formed in differing physical environments. It is pointed out that more data on the frequency with which globular clusters occur in elliptical galaxies might place interesting constraints on theories of galaxy clustering.Intercomparison of the Local Group galaxies IC 1613 and the SMC shows that differences in the frequency of cluster formation also occur among Irregular galaxies.It is pointed out that globular clusters associated with distant galaxies probably start to outnumber galactic stars for B > 31.The discovery that the LMC supernova remnant N63A is situated in the small association N2030 shows that this object must have been formed from a star with a main sequence mass > 30 M⊙.Finally we show that E3, which is one of the faintest known galactic globular cluster, was decimated by tidal forces. Due to the interplay of equipartition and tidal effects this cluster has been severely depleted in single stars while retaining many (presumably binary) blue stragglers.

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Globular Cluster Specific Frequencies in Coma

Symposium - International Astronomical Union ◽

10.1017/s0074180900224042 ◽

2002 ◽

Vol 207 ◽

pp. 348-350

Author(s):

A. Marín-Franch ◽

A. Aparicio

Keyword(s):

Globular Cluster ◽

Globular Clusters ◽

Surface Brightness ◽

Elliptical Galaxies ◽

Cluster Systems ◽

La Palma ◽

Surface Brightness Fluctuations ◽

Specific Frequency ◽

Individual Galaxy

Globular cluster systems (GCSs) have been observed in 17 elliptical galaxies located in Coma. Surface brightness fluctuations (SBF) and a 2.5-m ground-based telescope (INT, La Palma) have been used to determine total populations of Globular clusters (GCs) and specific frequency (SN) has been evaluated for each individual galaxy.

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