INVESTIGADORES
PIATTI Andres Eduardo
artículos
Título:
Fundamental parameters of the LMC clusters NGC 1836, NGC 1860, NGC 1865, SL 444, LW 224 and SL 548
Autor/es:
PIATTI, ANDRÉS E.; BICA, EDUARDO; GEISLER, DOUG; CLARIA OLMEDO, JUAN JOSÉ
Revista:
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Referencias:
Año: 2003 vol. 344 p. 965 - 977
ISSN:
0035-8711
Resumen:
Complementing our recent Washington photometric studies on intermediate
age and young Large Magellanic Cloud (LMC) clusters, we now turn our
attention to six previously unstudied star clusters in the transition
range 200-700 Myr. We study NGC 1836, 1860 and 1865, which are projected
on the LMC bar; SL 444, also located in the central disc but outside the
bar; and LW 224 and SL 548, both located in the outer disc. We derive
ages and metallicities from extracted T1 versus
C-T1 colour-magnitude diagrams (CMDs), using theoretical
isochrones recently computed for the Washington photometric system. For
the metallicity determinations, these CMDs are particularly sensitive.
We also estimate ages and metallicities of the surrounding fields of NGC
1860 and 1865 by employing the δT1 index defined in
Geisler et al. (1997, AJ, 114, 1920) and theoretical isochrones. By
adding the present cluster sample to those of our previous studies, we
now gather 37 LMC clusters with homogeneous parameter determinations,
which are employed to probe the chemical enrichment of the LMC and its
spatial distribution. On average, inner disc clusters turned out to be
not only younger than the outer ones, but also more metal-rich; some
have solar metal content. Furthermore, inner clusters located to the
west of the LMC centre are younger and more metal-rich than their
eastern counterparts. We propose that a bursting formation mechanism,
with an important formation event centred at ~2.0 Gyr, provides a better
description of the cluster age-metallicity relation than a closed-box
chemical evolution model. In the outer disc, the field star formation
seems to have lasted until 2 Gyr ago while it continued in the inner
disc for almost 1 Gyr longer.