34,413 research outputs found
The Star Cluster Systems of the Magellanic Clouds
The characteristics of the cluster systems of the Magellanic Clouds, as
inferred from integrated properties, are compared with those from individual
cluster studies and from the field population. The agreement is generally
satisfactory though in the case of the LMC, the lack of clusters older than ~3
Gyr is not reflected in the field population. The possible origin(s) for this
cluster ``age-gap'' are discussed. The SMC cluster age-metallicity relation is
also presented and discussed.Comment: 11 pages, 4 figures. To appear in the Proceedings of IAU Symposium
207, "Extragalactic Star Clusters", eds E. Grebel, D. Geisler and D. Minnit
A Second Shell in the Fornax dSph Galaxy
In the search for tidal structure in Galactic satellite systems, we have
conducted a photometric survey over a 10 square degree area centred on the
Fornax dSph galaxy. The survey was made in two colours, and the resulting
colour-magnitude data were used as a mask to select candidate Fornax RGB stars,
thereby increasing the contrast of Fornax stars to background sources in the
outer regions. Previously, we reported the presence of a shell (age 2 Gyr)
located towards the centre of Fornax. In this contribution we reveal a second
shell, significantly larger than the first, located 1.3 degrees NW from the
centre of Fornax, outside the nominal tidal radius. Moreover, the distribution
of Fornax RGB stars reveals two lobes extending to the spatial limit of our
survey, and aligned with the minor axis and with the two shells. These results
support the hypothesis of a merger between Fornax and a gas-rich companion
approximately 2 Gyr ago.Comment: Four pages,accepted for the Publications of the Astronomical Society
of Australia. Contribution the annual ASA meeting, Brisbane 200
Stability of a two-sublattice spin-glass model
We study the stability of the replica-symmetric solution of a two-sublattice
infinite-range spin-glass model, which can describe the transition from
antiferromagnetic to spin glass state. The eigenvalues associated with
replica-symmetric perturbations are in general complex. The natural
generalization of the usual stability condition is to require the real part of
these eigenvalues to be positive. The necessary and sufficient conditions for
all the roots of the secular equation to have positive real parts is given by
the Hurwitz criterion. The generalized stability condition allows a consistent
analysis of the phase diagram within the replica-symmetric approximation.Comment: 21 pages, 5 figure
Clarification of the Nature of the Galaxy CFC97 Cen 05
The galaxy CFC97 Cen 05 has in the past been considered an HI-rich dwarf
galaxy in the nearby Centaurus A group. We have used Australia Telescope
Compact Array observations to show that the HI associated with CFC97 Cen 05 by
Cote et al. (1997) is most likely a Galactic High Velocity Cloud that is
centered ~17' from the optical image of the galaxy. At the optical location of
the galaxy, which is not that tabulated by Banks et al. (1999), there is no
indication of the presence of HI for velocities less than the upper limit of
the HIPASS survey at ~12,500 km/s. In addition, WFPC2 images of CFC97 Cen 05
obtained from the HST Archive reveal that this galaxy is in fact not a dwarf at
all, but rather is a distant background spiral not associated with the
Centaurus A group.Comment: accepted for publication in the PASP (November 2004
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