INVESTIGADORES
FAIFER Favio Raul
artículos
Título:
Globular clusters as tracers of stellar bimodality in elliptical galaxies: the case of NGC 1399.
Autor/es:
FORTE, JUAN C.; FAIFER, FAVIO; GEISLER, DOUG
Revista:
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Editorial:
Blackwell Publishing
Referencias:
Lugar: Londres; Año: 2005 vol. 357 p. 56 - 68
ISSN:
0035-8711
Resumen:
Globular cluster systems (GCSs) frequently show a bimodal distribution
of cluster integrated colours. This work explores the arguments to
support the idea that the same feature is shared by the diffuse stellar
population of the galaxy they are associated with. The particular case
of NGC 1399, one of the dominant central galaxies in the Fornax cluster,
for which a new B surface brightness profile and (B-RKC)
colours are presented, is discussed taking advantage of a recently
published wide-field study of its GCS. The results show that the galaxy
brightness profile and colour gradient, as well as the behaviour of the
cumulative globular cluster specific frequency, are compatible with the
presence of two dominant stellar populations, associated with the
so-called `blue' and `red' globular cluster families. These globular
families are characterized by different intrinsic specific frequencies
(defined in terms of each stellar population): Sn= 3.3 +/-
0.3 in the case of the red globulars and Sn= 14.3 +/- 2.5 for
the blue ones. We stress that this result does not necessarily conflict
with recent works that point out a clear difference between the
metallicity distribution of (resolved) halo stars and globulars when
comparing their number statistics. The region within 0.5arcmin of the
centre shows a deviation from the model profile (in both surface
brightness and colour) that may be explained in terms of the presence of
a bulge-like high-metallicity component. Otherwise, the model gives an
excellent fit up to 12arcmin (or 66.5Kpc) from the centre, the
galactocentric limit of our blue brightness profile. The inferred
specific frequencies imply that, in terms of their associated stellar
populations, the formation of the blue globulars took place with an
efficiency about six times higher than that corresponding to their red
counterparts. The similarity of the spatial distribution of the blue
globulars with that inferred for dark matter, as well as with that of
the X-ray-emitting hot gas associated with NGC 1399, is emphasized. The
impact of a relatively inconspicuous low-metallicity population, that
shares the properties of the blue globulars, as a possible source of
chemical enrichment early in the formation history of the galaxy is also
briefly discussed.