Fundación Galileo Galilei - INAF Telescopio Nazionale Galileo 28°45'14.4N 17°53'20.6W 2387.2m A.S.L.

A new Galactic globular cluster identified by using DOLoRes-TNG data

Observational data taken in June 2008 with DOLoRes-TNG led to the identification in our Galaxy of a new interesting globular cluster.

This star system, known as Pfleiderer 2, was discovered in 1977 and classified as a open cluster projected in a rich star field. Recently, BVI photometry performed with DOLoRes allowed to draw its color-magnitude diagrams (CMDs) and to reveal its true nature.

The main CMD features of Pfleiderer 2 are a tilted red giant branch, and a red horizontal branch. Isochrone fits are compatible with an age within the range 8-12 Gyr, typical of globular clusters. The interesting finding is that it exhibits a nearly solar metallicity. This makes of this star system one of the few metal-rich globular clusters known in the Milky Way.

Contrary to classical globular clusters, Pfleiderer 2 is a relatively low-mass system, making part of a recently discovered class of low-luminosity, obscured, metal-rich globular clusters.

(S. Ortolani et al., "Pfleiderer 2: Identification of A New Globular Cluster in the Galaxy", 2009, Astronomical Journal, vol. 138, pages 889-894)

Figure 1. i'-band image of Pfleiderer 2 taken with DOLoRes-TNG (field 6 by 6 arcmin, North at the top and East to the left).