| dc.description.abstract | The Magellanic System at a distance of 50 kpc from the Milky Way (MW),
is a prime target in the study of stellar populations, star formation histories and
galactic dynamics in low metallicity environments. The Large Magellanic Cloud
(LMC) and Small Magellanic Cloud (SMC) have been observed in great depth,
however there has been somewhat less interest in the Magellanic Bridge connecting
the two and only more recently has the interest surged in the Magellanic Stream,
which trails the Clouds between them and the MW.
The Magellanic Bridge has a known younger stellar population dating back to Irwin’s
observations (Irwin et al., 1990), only more recently has an older population
been confirmed in the Bridge by Bagheri et al. (2013) and No¨el et al. (2013), while
the Magellanic Stream is known to contain gas only with no stellar component.
The estimated ages of the Bridge and Stream are 200 Myr (Bekki, 2007) and 2
Gyr (Diaz and Bekki, 2012) respectively, with the postulated Bridge formation
from a tidal interaction between the Clouds. The formation of the Stream is less
well understood with different models using varying assumptions and parameters
such as Besla et al. (2012) and Nidever et al. (2010), including possibilities that
the Clouds were historically bound or un-bound, and that the MW may or may
not have been involved in the Stream formation.
The work in this thesis makes use of different methods of removing the Galactic
foreground population in the direction of the Magellanic Bridge and Stream to
create cleaned catalogues of these regions. Various methods of analysis are applied
to the cleaned catalogues in this work to identify stellar populations in the
Bridge and Stream and density variations in the Bridge, including the production
of CMDs and two-colour diagrams, fitting isochrones to the observational data,
creating stellar density maps and studying spatial variations.
This work contains the first published confirmation that the Bridge contains an
older population of stars from public catalogues, which is supported with observations
of the older population in recent deeper surveys, and confirmed with
spectroscopic follow up observations. The young population has ages within the
age of the Bridge ( 200 − 500 Myr) and are likely to have formed in-situ, in
regions of high density gas closest to the SMC. The number of young blue objects
in the Bridge tiles is greater towards the SMC and decreases towards the LMC.
Populations identified here reach ages up to 3 Gyr are likely to have been drawn
into the Bridge from the Clouds at formation.
The key results from this work are that an older Bridge stellar population has
been identified and confirmed, indicating that stars as well as gas were drawn into
the Bridge at its creation. The fact that the younger population has the highest
density away from the main concentration of hydrogen show that the gas within
the Bridge has been displaced by ram pressure, most likely due to the Clouds
moving through the Galactic halo. Less concrete results in this work reveal a puzzling
populetion of objects within the Magellanic Stream, which could be stellar in
nature and with follow up work, could be the first observation of Stream objects.
This work contributes to our understanding of the interaction between the LMC
and SMC via the Stellar populations between them. | en_US |
