Terzan 8: a Sagittarius-flavoured globular cluster^{⋆,⋆⋆,⋆⋆⋆}

¹ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
e-mail: eugenio.carretta@oabo.inaf.it
² INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
³ Dept. of Physics and Astronomy, Macquarie University, Sydney, NSW 2109, Australia
⁴ Monash Centre for Astrophysics, Monash University, School of Mathematical Sciences, Building 28, Clayton VIC 3800, Melbourne, Australia

Received: 16 September 2013
Accepted: 6 November 2013

Abstract

Massive globular clusters (GCs) contain at least two generations of stars with slightly different ages and clearly distinct light element abundances. The Na-O anticorrelation is the best studied chemical signature of multiple stellar generations. Instead, low-mass clusters usually appear to be chemically homogeneous. We are investigating low-mass GCs to understand what the lower mass limit is where multiple populations can form, mainly using the Na and O abundance distribution. We used VLT/FLAMES spectra of giants in the low-mass, metal-poor GC Terzan 8 that belongs to the Sagittarius dwarf galaxy to determine abundances of Fe, O, Na, α-, Fe-peak, and neutron-capture elements in six stars observed with UVES and 14 observed with GIRAFFE. The average metallicity is [Fe/H] = −2.27 ± 0.03 (rms = 0.08), based on the six high-resolution UVES spectra. Only one star, observed with GIRAFFE, shows an enhanced abundance of Na and we tentatively assign it to the second generation. In this cluster, unlike what happens in more massive GCs, the second generation seems to represent at most a minority fraction. We discuss the implications of our findings, comparing Terzan 8 with the other Sgr dSph GCs, and to GCs and field stars in the Large Magellanic Cloud, Fornax, and in other dwarfs galaxies.