Blue stragglers in dwarf galaxies

Plot
Figure 1:The Blue Stragglers (BSS) frequency as a function of the luminosity of the systems. Note how the frequency in dwarf galaxies is always higher than that in globular clusters.

BSS are easily identified in globular and open clusters. In a recent paper Momany et al.  (A&A, 2007) we addressed the specific frequency of BSS in dwarf galaxies. Against all expectations, we find that the BSS in a sample of dwarf spheroidal (non star-forming) galaxies is higher with respect to that in globular cluster with the same luminosity. This confirms that loose-density environments (like that of dwarf galaxies) provide a more "friendly" survival conditions for primordial binaries. Despite their extremely low production of collisional binaries, dwarf galaxies still outcome the total BSS fraction present in globulars.

The implications of this result are now being examined from 2 particular aspects: (i) the impact of a higher BSS population on the properties of distant un-resolved galaxies (e.g. integral photometric indexes and age derivation); and (ii) the impact of a higher BSS population on the so-called UV-upturn in elliptical galaxies.

People: Y. Momany, S. Zaggia, E.V. Held, M. Gullieuszik

Collaboration: I. Saviane (ESO, Chile), L. Rizzi (Honolulu, USA)

Publications: see text

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