Extended Structures in Globular Clusters
Date
2017
Authors
Kuzma, Pete
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Abstract
Our view and understanding of globular clusters in the Milky Way
have undergone massive changes over the past few decades. No
longer are globular clusters seen as the perfect example of
simple stellar populations, as almost all Galactic globular
clusters are now known to contain star-to-star light element
abundance variations, and a small subset contain heavy element
abundance ranges. However, not only can a lot be learnt from
studying the stars within globular clusters, but also from the
stars outside globular clusters, beyond the tidal radius. Whether
the structure is in the form of tidal tails such as the iconic
tails of Palomar 5, or part of a much larger scale stellar
feature such as the stellar stream belonging to the disrupting
dwarf galaxy Sagittarius or the wealth of streams in the halo of
M31, the environs of Galactic globular clusters can be used as
insights into the formation of the globular clusters themselves
and to the shape and formation of the Milky Way’s halo.
This thesis focuses on exploring extended features of Milky Way
globular clusters. First, by increasing the spatial coverage and
kinematics of the tidal tails of Palomar 5 through low to
intermediate resolution spectroscopy from the 2df AAOmega
spectrograph on the Anglo-Australian Telescope. We identify 39
new and recover 8 previously deter- mined members in the tidal
stream through radial velocities, line strengths and photomet-
ric information.
Second, we performed a wide field photometric survey of southern
Galactic globular clusters with the complementary imagers MegaCam
on the 6.5m Clay Telescope, and the DECam, on the 4m Blanco
Telescope. We present the results for the four clusters analysed
during the PhD candidature: NGC 1261, NGC 1851, NGC 5824 and NGC
7089 (M2). We find diffuse large low surface density envelopes
containing NGC 1261, NGC 1851 and M2, with a tentative detection
of an envelope surrounding NGC 5824. We discuss the origins of
the envelopes and how the features we have uncovered, along with
Palomar 5’s tidal tails, may influence our understanding of the
Galactic halo and globular cluster formation.
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Keywords
Astronomy, Globular Clusters, Astrophysics, Tidal Tails, Stellar Envelopes, Galaxy
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Thesis (PhD)
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