THE M33 GLOBULAR CLUSTER SYSTEM WITH PAndAS DATA: THE LAST OUTER HALO CLUSTER?

Cockcroft, Robert; Harris, William E.; Ferguson, Annette M. N.; Huxor, Avon; Ibata, Rodrigo; Irwin, M. J.; McConnachie, Alan W.; Woodley, Kristin A.; Chapman, Scott; Lewis, Geraint F.; Puzia, Thomas H.

doi:10.1088/0004-637x/730/2/112

Cited by 36 publications

(41 citation statements)

References 63 publications

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“…The most compact objects include the classical population of GCs with r h ∼ 2-4 pc, the UCDs which extend up to r h ∼ 50 pc, and the fainter ECs up to r h ∼ 25 pc, which comprise not only ECs (Huxor et al 2005(Huxor et al , 2008(Huxor et al , 2009(Huxor et al , 2011aMackey et al 2006;Stonkutė et al 2008;Mouhcine et al 2010;Cockcroft et al 2011;Hwang et al 2011), but also faint fuzzies (Larsen & Brodie 2000;Sharina et al 2005;Hwang & Lee 2006, 2008Chies-Santos et al 2007;Scheepmaker et al 2007), "diffuse star clusters" (Peng et al 2006), and the Palomar clusters in the Milky Way halo.…”

Section: Size and Luminosity Comparisonsmentioning

confidence: 99%

The Relationships Among Compact Stellar Systems: A Fresh View of Ultracompact Dwarfs

Brodie

Romanowsky

Strader

et al. 2011

The Astronomical Journal

206

311

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We use a combined imaging and spectroscopic survey of the nearby central cluster galaxy, M87, to assemble a sample of 34 confirmed ultracompact dwarfs (UCDs) with half-light radii of 10 pc measured from Hubble Space Telescope images. This doubles the existing sample in M87, making it the largest such sample for any galaxy, while extending the detection of UCDs to unprecedentedly low luminosities (M V = −9). With this expanded sample, we find no correlation between size and luminosity, in contrast to previous suggestions, and no general correlation between size and galactocentric distance. We explore the relationships between UCDs, less luminous extended clusters (including faint fuzzies), globular clusters (GCs), as well as early-type galaxies and their nuclei, assembling an extensive new catalog of sizes and luminosities for stellar systems. Most of the M87 UCDs follow a tight color-magnitude relation, offset from the metal-poor GCs. This, along with kinematical differences, demonstrates that most UCDs are a distinct population from normal GCs, and not simply a continuation to larger sizes and higher luminosities. The UCD color-magnitude trend couples closely with that for Virgo dwarf elliptical nuclei. We conclude that the M87 UCDs are predominantly stripped nuclei. The brightest and reddest UCDs may be the remnant nuclei of more massive galaxies while a subset of the faintest UCDs may be tidally limited and related to more compact star clusters. In the broader context of galaxy assembly, blue UCDs may trace halo build-up by accretion of low-mass satellites, while red UCDs may be markers of metal-rich bulge formation in larger galaxies.

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Section: Size and Luminosity Comparisonsmentioning

confidence: 99%

The Relationships Among Compact Stellar Systems: A Fresh View of Ultracompact Dwarfs

Brodie

Romanowsky

Strader

et al. 2011

The Astronomical Journal

206

311

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“…The other two Local Group spiral A65, page 2 of 17 galaxies M 31 and M 33 have 20 (Huxor et al 2008;Peacock et al 2009;Huxor et al 2011a) and 2 (Stonkutė et al 2008;Cockcroft et al 2011) EOs, respectively. EOs were also found in the LMC (van den Bergh & Mackey 2004), and the dwarf irregular galaxy NGC 6822 (Hwang et al 2011).…”

Section: Eos In Late-type Galaxiesmentioning

confidence: 99%

A catalog of extended clusters and ultra-compact dwarf galaxies

Kroupa

2012

A&A

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Context. In the past decade, very extended old stellar clusters with masses in the range from a few 10 4 to 10 8 M and effective radii larger than 10 pc have been found in various types of galaxies in different environments. Objects with masses comparable to normal globular clusters (GCs) are called extended clusters (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies (UCDs). Aims. The paper analyses the observational parameters total luminosity, M V , effective radius, r eff , and projected distance to the host galaxy, R proj , of all known ECs and UCDs and the dependence of these parameters on the type and the total luminosity of their host galaxy. Methods. We searched the available literature to compile a catalog of star clusters with effective radii larger than 10 pc. As there is no clear distinction between ECs and UCDs, both types of objects will be called extended stellar objects -abbreviated "EOs" -in this paper.Results. In total, we found 813 EOs of which 171 are associated with late-type galaxies and 642 EOs associated with early-type galaxies. EOs cover a luminosity range from about M V = −4 to −14 mag. However, the vast majority of EOs brighter than M V = −10 mag are associated with giant elliptical galaxies. At each magnitude extended objects are found with effective radii between 10 pc and an upper size limit, which shows a clear trend: the more luminous the object the larger is the upper size limit. For EOs associated with early-and late-type galaxies, the EO luminosity functions peak at −6.40 mag and −6.47 mag, respectively, which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the r eff vs. M V parameter space, while there is a clear gap between EOs and early-type dwarf galaxies. However, there is a small potential overlap at the high-mass end, where the most extended EOs are close to the parameters of some compact elliptical galaxies. We compare the EO sample with the numerical models of a previous paper and conclude that the parameters of the EO sample as a whole can be very well explained by a star cluster origin, where EOs are the results of merged star clusters of cluster complexes.

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“…These authors presented that the four M33 clusters have similar structural parameters and fall in the same "fundamental plane" (FP) and binding energyluminosity relations as the Milky Way and M31 clusters. Cockcroft et al (2011) measured the structural parameters of six outer clusters of M33 by fitting the models of King (1962King ( , 1966 and of Wilson (1975), using the Canada-France-Hawaii Telescope/MegaCam data as part of the Pan-Andromeda Archaeological Survey. The structural parameters obtained by Cockcroft et al (2011) include the concentration parameter and the core, half-light, and tidal radii.…”

Section: Introductionmentioning

confidence: 99%

“…Cockcroft et al (2011) measured the structural parameters of six outer clusters of M33 by fitting the models of King (1962King ( , 1966 and of Wilson (1975), using the Canada-France-Hawaii Telescope/MegaCam data as part of the Pan-Andromeda Archaeological Survey. The structural parameters obtained by Cockcroft et al (2011) include the concentration parameter and the core, half-light, and tidal radii. San Roman et al (2012) presented detailed morphological properties of M33 star clusters using the HST images.…”

Section: Introductionmentioning

confidence: 99%

Structural Parameters for 10 Halo Globular Clusters in M33

2015

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In this paper, we present the properties of 10 halo globular clusters (GCs) with luminosities L ; 5-7 × 10 5 L e in the Local Group galaxy M33 using images from the Hubble Space Telescope WFPC2 in the F555W and F814W bands. We obtained the ellipticities, position angles, and surface brightness profiles for each GC. In general, the ellipticities of the M33 sample clusters are similar to those of the M31 clusters. The structural and dynamical parameters are derived by fitting the profiles to three different models combined with mass-to-light ratios (M/L values) from population-synthesis models. The structural parameters include core radii, concentration, half-light radii, and central surface brightness. The dynamical parameters include the integrated cluster mass, integrated binding energy, central surface mass density, and predicted line of sight velocity dispersion at the cluster center. The velocity dispersions of the four clusters predicted here agree well with the observed dispersions by Larsen et al. The results here showed that the majority of the sample halo GCs are better fitted by both the King model and the Wilson model than the Sérsic model. In general, the properties of the clusters in M33, M31, and the Milky Way fall in the same regions of parameter spaces. The tight correlations of cluster properties indicate a "fundamental plane" for clusters, which reflects some universal physical conditions and processes operating at the epoch of cluster formation.

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THE M33 GLOBULAR CLUSTER SYSTEM WITH PAndAS DATA: THE LAST OUTER HALO CLUSTER?

Cited by 36 publications

References 63 publications

The Relationships Among Compact Stellar Systems: A Fresh View of Ultracompact Dwarfs

The Relationships Among Compact Stellar Systems: A Fresh View of Ultracompact Dwarfs

A catalog of extended clusters and ultra-compact dwarf galaxies

Structural Parameters for 10 Halo Globular Clusters in M33

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