Juan C. Forte, E. Irene Vega, Favio R. Faifer
As shown in previous works, globular clusters can be used to trace the
overall structure of the diffuse stellar populations in early type galaxies if
the number of clusters per unit stellar mass depends on metallicity. In this
paper we further test this assumption in the galaxy NGC 4486 (M 87), by
combining several data sources. The results show that globular clusters allow
the mapping of the galaxy in terms of the surface brightness profile,
integrated colour gradient, chemical abundance, and mass to luminosity ratios
up to 1000 arcsec (or 80.4 kpc) from its centre (i.e. some 10 effective radii).
The analysis indicates the presence of a dominant high metallicity bulge
associated with the red globulars, whose ellipticity increases outwards, and of
a more flattened low metallicity halo connected with the blue globulars. The
chemical abundance gradient of the composite stellar population is remarkably
similar to that inferred from X ray observations of hot gas. The
mass-metallicity spectrum of the stellar population can, in principle, be
understood in terms of inhomogeneous enrichment models. In turn, the
distribution of the bluest GCs, and lowest metallicity halo stars, has an
intriguing similarity with that of dark matter, a feature shared with NGC 1399.
Also, in these two galaxies, the number of blue GCs per dark mass unit is
identical within the errors, \approx 1.0(\pm0.3) \times 10^{-9} . The total
stellar mass derived for NGC 4486 is 6.8(\pm1.1) \times 10^{11} M\odot with a
baryonic mass fraction fb = 0.08(\pm 0.01).
View original:
http://arxiv.org/abs/1112.1884
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