UV insights into the complex populations of M87 globular clusters

Journal Article · Mon Jun 01 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/805/2/178· OSTI ID:22879390

Bellini, A.; Anderson, J.; Soto, M.; Brown, T. M. ^[1]; Renzini, A.; Bedin, L. R.; Piotto, G. ^[2]; Milone, A. P. ^[3]; Sohn, S. T. ^[4]

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1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2. INAF—Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, I-35122 Padova (Italy)
3. Research School of Astronomy and Astrophysics, Australian National University, Mt Stromlo Observatory, via Cotter Rd, Weston, ACT 2611 (Australia)
4. Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)

We have imaged with Hubble Space Telescope WFC3/UVIS the central 2.7' x 2.7' region of the giant elliptical galaxy M87, using the ultraviolet filter F275W. In combination with archival ACS/WFC data taken through the F606W and F814W filters, covering the same field, we have constructed integrated-light UV–optical colors and magnitudes for 1460 objects, most of which are believed to be globular clusters (GCs) belonging to M87. The purpose was to ascertain whether the multiple-populations syndrome, ubiquitous among Galactic GCs, also exists among the M87 family of clusters. To achieve this goal, we sought those GCs with exceptionally blue UV-to-optical colors because helium-enriched sub-populations produce a horizontal-branch morphology that is well populated at high effective temperature. For comparison, integrated, synthetic UV–optical and purely optical colors and magnitudes have been constructed for 45 Galactic GCs, starting from individual-star photometry obtained with the same instruments and the same filters. We identify a small group of M87 clusters exhibiting a radial UV–optical color gradient, representing our best candidate GCs hosting multiple populations with extreme helium content. We also find that the central spatial distribution of the bluer GCs is flattened in a direction parallel to the jet, while the distribution of redder GCs is more spherical. We release to the astronomical community our photometric catalog in F275W, F606W, and F814W bands and the high-quality image stacks in the same bands.

• OSTI ID: 22879390
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 805; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPARATIVE EVALUATIONS
FILTERS
GALAXIES
HELIUM
JETS
MORPHOLOGY
PHOTOMETRY
SPACE
SPATIAL DISTRIBUTION
SPHERICAL CONFIGURATION
STAR CLUSTERS
TELESCOPES
ULTRAVIOLET RADIATION