N. Sanna, E. Dalessandro, B. Lanzoni, F. R. Ferraro, G. Beccari, R. T. Rood
We have used a combination of high-resolution Hubble Space Telescope WFPC2
and wide-field ground-based observations in ultraviolet and optical bands to
study the blue straggler star (BSS) population of the outer-halo globular
cluster NGC 6229, over its entire radial extent. A total of 64 bright BSS (with
m255 6 21.30, corresponding to m555 6 20.75) has been identified. The BSS
projected radial distribution is found to be bimodal, with a high central peak,
a well defined minimum at intermediate radii (r \sim 40"), and an upturn in the
outskirts. From detailed star counts even in the very inner region, we compute
the centre of gravity of the cluster and the most accurate and extended radial
density profile ever published for this system. The profile is reasonably well
reproduced by a standard King model with an extended core (rc \simeq 9.5") and
a modest value of the concentration parameter (c \simeq 1.49). However, a
deviation from the model is noted in the most external region of the cluster
(at r > 250" from the centre). This feature needs to be further investigated in
order to assess the possible presence of a tidal tail in this cluster.
View original:
http://arxiv.org/abs/1202.1094
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