The blue plume population in dwarf spheroidal galaxies: young stellar population or genuine blue stragglers?

TL;DR

This study investigates whether the blue plume stars in dwarf spheroidal galaxies are genuine blue stragglers or young stars, finding that their high frequency and environment suggest they are predominantly genuine blue stragglers formed in low-density conditions.

Contribution

It provides the first comparative analysis of blue straggler frequency in dwarf spheroidal galaxies versus globular clusters and halo, highlighting the role of environment in BSS formation.

Findings

BSS frequency in dwarf galaxies exceeds that in globular clusters of similar luminosity.

Low-density environments in dwarf galaxies lead to negligible collisional BSS production.

BSS frequency in faint dwarf galaxies matches that in the Milky Way halo and open clusters.

Abstract

In the context of dwarf spheroidal galaxies it is hard to firmly disentangle a genuine Blue Stragglers (BSS) population from a normal young main (MS) sequence. This difficulty is persistent. For a sample of 9 non-star forming Local Group dwarf galaxies we compute the ``BSS frequency'' and compare it with that found in the Milky Way globular/open clusters and halo. The comparison shows that the BSS-frequency in dwarf galaxies, at any given Mv, is always higher than that in globular clusters of similar luminosities. Moreover, the estimated BSS-frequency for the lowest luminosity dwarf galaxies is in excellent agreement with that observed in the Milky Way halo and open clusters. We conclude that the low density, almost collision-less environment, of our dwarf galaxy sample point to their very low dynamical evolution and consequent negligible production of collisional BSS.