Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Galactic Globular Cluster Relative Ages   Based on a new large, homogeneous photometric database of 35 Galactic
globular clusters (GGCs), a set of distance and reddening independent relative
age indicators has been measured. The observed D(V-I)_2.5 and D(V)(HB-TO) vs.
metallicity relations have been compared with the relations predicted by two
recent updated libraries of isochrones. Using these models and two independent
methods, we have found that self-consistent relative ages can be estimated for
our GGC sample. Based on the relative age vs. metallicity distribution, we
conclude that: (a) there is no evidence of an age spread for clusters with
[Fe/H]<-1.2, all the clusters of our sample in this range being old and coeval;
(b) for the intermediate metallicity group (-1.2<=[Fe/H]<-0.9) there is a clear
evidence of age dispersion, with clusters up to ~25% younger than the older
members; and (c) the clusters within the metal rich group ([Fe/H]>=-0.9) seem
to be coeval within the uncertainties (except Pal12), but younger (~17%) than
the bulk of the Galactic globulars. The latter result is totally model
dependent. From the distribution of the GGC ages with the Galactocentric
distance, we can present a possible scenario for the Milky Way formation: The
GC formation process started at the same zero age throughout the halo, at least
out to ~20 kpc from the Galactic center. According to the present stellar
evolution models, the metal-rich globulars are formed at a later time (~ 17%
lower age). And finally, significantly younger halo GGCs are found at any
R(GC)>8 kpc. For these, a possible scenario associated with mergers of dwarf
galaxies to the Milky Way is suggested.

9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess
2
The categories of this paper are: math
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs