Globular cluster scale sizes in giant galaxies: orbital anisotropy and tidally underfilling clusters in M87, NGC 1399 and NGC 5128

Webb, Jeremy J.; Sills, Alison; Harris, William E.; Gómez, M.; Paolillo, M.; Woodley, Kristin A.; Puzia, Thomas H.

doi:10.1093/mnras/stw1115

Cited by 8 publications

(7 citation statements)

References 105 publications

(208 reference statements)

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“…Similar trends are detected in the ancient globular clusters of the Large Magellanic Cloud (Piatti & Mackey 2018), whose sizes, Elson et al (1987)'s power-law slopes at large radii (γ, Mackey & Gilmore 2004), ratios of the cluster radius to Jacobi radius, and the inverse of the concentration parameter c increase with the deprojected galactocentric distance. Similar trends are also seen in giant elliptical galaxies (Harris 2009;Webb et al 2016). Heggie & Hut (2003) have described the internal dynamics evolution of a star cluster as seen in the rc/r h versus r h /rJ plane.…”

Section: Analysis and Discussionsupporting

confidence: 80%

“…More specifically, rc, r h and rJ all increase with semi-major axis at different paces and the spread in radius ), ratios of the cluster radius to Jacobi radius, and the inverse of the concentration parameter c increase with the deprojected galactocentric distance. Similar trends are also seen in giant elliptical galaxies (Harris 2009;Webb et al 2016). Heggie & Hut (2003) have described the internal dynamics evolution of a star cluster as seen in the rc/r h versus r h /rJ plane.…”

Section: Analysis and Discussionsupporting

confidence: 65%

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Characteristic radii of the Milky Way globular clusters

Piatti

Webb

Carlberg

2019

Monthly Notices of the Royal Astronomical Society

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We report on the extent of the effects of the Milky Way's gravitational field in shaping the structural parameters and internal dynamics of its globular cluster population. We make use of a homogeneous, up-to-date data set with kinematics, structural properties, current and initial masses of 156 globular clusters. In general, cluster radii increase as the Milky Way potential weakens; with the core and Jacobi radii being those which increase at the slowest and fastest rate respectively. We interpret this result as the innermost regions of globular clusters being less sensitive to changes in the tidal forces with the Galactocentric distance. The Milky Way's gravitational field also seems to have differentially accelerated the internal dynamical evolution of individual clusters, with those toward the bulge appearing dynamically older. Finally we find a sub-population consisting of both compact and extended globular clusters (as defined by their r h /r J ratio) beyond 8 kpc that appear to have lost a large fraction of their initial mass lost via disruption. Moreover, we identify a third group with r h /r J > 0.4, which have lost an even larger fraction of their initial mass by disruption. In both cases the high fraction of mass lost is likely due to their large orbital eccentricities and inclination angles, which lead to them experiencing more tidal shocks at perigalacticon and during disc crossings. Comparing the structural and orbital parameters of individual clusters allows for constraints to be placed on whether or not their evolution was relaxation or tidally dominated.

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Section: Analysis and Discussionsupporting

confidence: 80%

Section: Analysis and Discussionsupporting

confidence: 65%

Characteristic radii of the Milky Way globular clusters

Piatti

Webb

Carlberg

2019

Monthly Notices of the Royal Astronomical Society

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“…But in this case the radii of star clusters should eventually reflect their local tidal gravitational fields that usually decrease with increasing galactocentric radius. Our results suggest that clusters across the range of mass, age, and environment covered by our samples do not show effects of tidal truncations in their half-light radii; otherwise, a stronger increase of cluster size with galactocentric distance is expected (e.g., Madrid et al 2012;Webb et al 2016).…”

Section: 0mentioning

confidence: 69%

Effective Radii of Young, Massive Star Clusters in Two LEGUS Galaxies^∗

Ryon

Gallagher

Smith

et al. 2017

ApJ

109

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We present a study of the effective (half-light) radii and other structural properties of a systematically selected sample of young, massive star clusters (5×10 3  M and 200Myr) in two nearby spiral galaxies, NGC628 and NGC1313. We use Hubble Space Telescope (HST) WFC3/UVIS and archival ACS/WFC data obtained by the Legacy Extragalactic UV Survey (LEGUS), an HST Treasury Program. We measure effective radii with GALFIT, a two-dimensional image-fitting package, and with a new technique to estimate effective radii from the concentration index of observed clusters. The distribution of effective radii from both techniques spans ∼0.5-10pc and peaks at 2-3pc for both galaxies. We find slight positive correlations between effective radius and cluster age in both galaxies, but no significant relationship between effective radius and galactocentric distance. Clusters in NGC1313 display a mild increase in effective radius with cluster mass, but the trend disappears when the sample is divided into age bins. We show that the vast majority of the clusters in both galaxies are much older than their dynamical times, suggesting they are gravitationally bound objects. We find that about half of the clusters in NGC628 are underfilling their Roche lobes, based on their Jacobi radii. Our results suggest that the young, massive clusters in NGC628 and NGC1313 are expanding, due to stellar mass loss or two-body relaxation, and are not significantly influenced by the tidal fields of their host galaxies.

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“…The complex GCS for these three large galaxies gives evidence that these galaxies had more active formation histories than the MW. Nevertheless, given the locations in sparsely populated regions, their formation histories were not as turbulent as those of cluster ellipticals, such as NGC 1399 (Puzia et al 2014;Webb et al 2016) A further difference we observed between NGC 3115 and NGC 1399 is related to the local specific frequency S N (< r), i.e., the S N value obtained from the magnitude and GC number integrated within a given radius, a relative comparison largely insensitive to any GC magnitude incompleteness. We observe a steady increase of S N (< r) blue for the blue GCs in NGC 3115, which is not unexpected given the way S N is defined, because the blue GC density profile is more extended than the galaxy light.…”

Section: Differences and Similaritiesmentioning

confidence: 72%

VEGAS-SSS. II. Comparing the globular cluster systems in NGC 3115 and NGC 1399 using VEGAS and FDS survey data

Cantiello¹,

D’Abrusco

Spavone

et al. 2018

A&A

Self Cite

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We analyze the globular cluster (GC) systems in two very different galaxies, NGC 3115 and NGC 1399. With the papers of this series, we aim at highlighting common and different properties in the GC systems in galaxies covering a wide range of parameter space. We compare the GCs in NGC 3115 and NGC 1399 as derived from the analysis of one square degree u−, g−, and i−band images taken with the VST telescope as part of the VST early-type galaxy survey (VEGAS) and Fornax deep survey (FDS). We selected GC candidates using as reference the morpho-photometric and color properties of confirmed GCs. The surface density maps of GCs in NGC 3115 reveal a morphology similar to the light profile of field stars; the same is true when blue and red GCs are taken separately. The GC maps for NGC 1399 are richer in structure and confirm the existence of an intra-cluster GC component. We confirm the presence of a spatial offset in the NGC 1399 GC centroid and find that the centroid of the GCs for NGC 3115 coincides well with the galaxy center. Both GC systems show unambiguous color bimodality in (g−i) and (u−i); the color-color relations of the two GC systems are slightly different with NGC 3115 appearing more linear than NGC 1399. The azimuthal average of the radial density profiles in both galaxies reveals a larger spatial extent for the total GCs population with respect to the galaxy surface brightness profile. For both galaxies, the red GCs have radial density profiles compatible with the galaxy light profile, while the radial profiles for blue GCs are shallower. As for the specific frequency of GCs, S N , we find it is a factor of two higher in NGC 1399 than for NGC 3115; this is mainly the result of extra blue GCs. By inspecting the radial behavior of the specific frequency, S N (< r), for the total, blue, and red GCs, we find notable similarities between the trends for red GCs in the two targets. In spite of extremely different host environments, the red GCs in both cases appear closely linked to the light distribution of field stars. Blue GCs extend to larger galactocentric scales than red GCs, marking a significant difference between the two galaxies: the blue/red GCs and field stellar components of NGC 3115 appear well thermalized with each other and the blue GCs in NGC 1399 appear to fade into an unrelaxed intra-cluster GC population.

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Globular cluster scale sizes in giant galaxies: orbital anisotropy and tidally underfilling clusters in M87, NGC 1399 and NGC 5128

Cited by 8 publications

References 105 publications

Characteristic radii of the Milky Way globular clusters

Characteristic radii of the Milky Way globular clusters

Effective Radii of Young, Massive Star Clusters in Two LEGUS Galaxies^∗

VEGAS-SSS. II. Comparing the globular cluster systems in NGC 3115 and NGC 1399 using VEGAS and FDS survey data

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Globular cluster scale sizes in giant galaxies: orbital anisotropy and tidally underfilling clusters in M87, NGC 1399 and NGC 5128

Cited by 8 publications

References 105 publications

Characteristic radii of the Milky Way globular clusters

Characteristic radii of the Milky Way globular clusters

Effective Radii of Young, Massive Star Clusters in Two LEGUS Galaxies∗

VEGAS-SSS. II. Comparing the globular cluster systems in NGC 3115 and NGC 1399 using VEGAS and FDS survey data

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Product

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Effective Radii of Young, Massive Star Clusters in Two LEGUS Galaxies^∗