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arXiv · 0909.0272

Structural Parameters of the M87 Globular Clusters

Juan P. Madrid·William E. Harris·John P. Blakeslee·Matias Gomez
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Abstract

We derive structural parameters for ~2000 globular clusters in the giant Virgo elliptical M87 using extremely deep Hubble Space Telescope images in F606W (V) and F814W (I) taken with the ACS/WFC. The cluster scale sizes (half-light radii r_h) and ellipticities are determined from PSF-convolved King-model profile fitting. We find that the r_h distribution closely resembles the inner Milky Way clusters, peaking at r_h~2.5 pc and with virtually no clusters more compact than r_h ~ 1 pc. The metal-poor clusters have on average an r_h 24% larger than the metal-rich ones. The cluster scale size shows a gradual and noticeable increase with galactocentric distance. Clusters are very slightly larger in the bluer waveband V a possible hint that we may be beginning to see the effects of mass segregation within the clusters. We also derived a color magnitude diagram for the M87 globular cluster system which show a striking bimodal distribution.

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Juan P. Madrid, William E. Harris, John P. Blakeslee, Matias Gomez. 2009-09-01. Structural Parameters of the M87 Globular Clusters. https://doi.org/10.1088/0004-637x/705/1/237

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