Articulo
Gemini/GMOS spectra of globular clusters in the Virgo giant elliptical NGC 4649
Autor
Pierce, Michael
Bridges, Terry
Forbes, Duncan A.
Proctor, Robert
Beasley, Michael A.
Gebhardt, Karl
Faifer, Favio Raúl
Forte, Juan Carlos
Zepf, Stephen E.
Sharpies, Ray
Hanes, David A.
Institución
Resumen
NGC 4649 (M60) is one of a handful of giant Virgo ellipticals. We have obtained Gemini/GMOS (Gemini North Multi-Object Spectrograph) spectra for 38 globular clusters (GCs) associated with this galaxy. Applying the multi-index χ<SUP>2</SUP> minimization technique of Proctor and Sansom with the single stellar population models of Thomas, Maraston and Korn, we derive ages, metallicities and α-element abundance ratios. We find several young (2-3 Gyr old) supersolar metallicity GCs, while the majority are old (>10 Gyr), spanning a range of metallicities from solar to [Z/H] = -2. At least two of these young GCs are at large projected radii of 17-20 kpc. The galaxy itself shows no obvious signs of a recent starburst, interaction or merger. A trend of decreasing α-element ratio with increasing metallicity is found. Facultad de Ciencias Astronómicas y Geofísicas Instituto de Astrofísica de La Plata