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Katherine Elizabeth Hollyhead Liverpool John Moores University THE FORMATION AND EVOLUTION OF MASSIVE CLUSTERS IN EXTRAGALACTIC ENVIRONMENTS Katherine Elizabeth Hollyhead Liverpool John Moores University A thesis submitted in partial fulfilment of the requirements of Liverpool John Moores University for the degree of Doctor of Philosophy. November 11, 2017 Declaration The work presented in this thesis was carried out at the Astrophysics Research Institute, Liver- pool John Moore’s University. Unless otherwise stated, it is the original work of the author. While registered as a candidate for the degree of Doctor of Philosophy, for which submission is now made, the author has not been registered as a candidate for any other award. This thesis has not been submitted in whole, or in part, for any other degree. Katherine E. Hollyhead Astrophysics Research Institute Liverpool John Moore’s University IC2, Liverpool Science Park 146 Brownlow Hill Liverpool L3 5RF UK i Abstract There are a host of open questions in the study of massive clusters relating to cluster formation and evolution. Understanding these processes can be useful in studying their host galaxies and how they have evolved. The formation of globular clusters is also a well debated topic, which is yet undecided and requires many more observations to constrain the theories. Here I present the work carried out during my PhD, with the goal of furthering our understand- ing of cluster formation and evolution using observations of massive clusters of various ages. Firstly, HST WFC3 data of the well studied face-on spiral galaxy M 83, combined with an ex- isting cluster catalogue, was used to investigate the timescale by which young massive clusters become free of gas. This has implications for globular cluster formation theories, in addition to the survival of clusters at young ages. The presence of Wolf-Rayet stars was also investigated within the clusters and the unreliability of Hα photometry in young cluster age and mass fitting was explored. Secondly, the cluster population of NGC 1566 was used to investigate the cluster mass function and disruption in the galaxy. Whether the mass function has a truncation in the form of a Schechter function and whether disruption is environmentally and mass dependent are two questions that still persist in this area. For NGC 1566 I find that the mass function does show a truncation and using the observed luminosity function in conjunction with models, that an underlying Schechter mass function fits the observations well. Additionally the galaxy shows evidence for environmentally dependent disruption as the average timescale for the disruption 4 of a 10 M cluster varies with galactocentric radius. A difference in age in radial bins is also indicated in a colour change found with U-B between consecutive bins, that shows more young clusters towards the centre of the galaxy and fewer at the edge. Finally, low resolution FORS2 spectra of two intermediate age massive clusters in the SMC ii (Lindsay 1 and Kron 3, 6-8 Gyr old) were used to look for the signatures of multiple populations (MPs), as observed in ancient GCs. The main driver behind this project was to investigate the possibility that YMCs can be considered young GCs and used to constrain their formation, and also to explore the role cluster age has in determining the presence of MPs. A subpopulation of N-enriched stars was found in each cluster, consistent with the presence of MPs. This indicates that MPs are not limited to ancient GCs and their formation mechanism must be operating until a redshift of at least 0.65, much later than the peak of GC formation at ≈ 3. It hints at a common formation mechanism between massive clusters of varying ages, including GCs, and suggests that YMCs can be used to constrain GC formation. The publications from these projects have contributed mainly to constraining GC formation theories and provides evidence for commonality in the formation mechanism used to produce GCs and YMCs alike. iii Acknowledgements I would firstly like to acknowledge the significant contributions made to the work in this thesis by others. I shall divide these into the chapters in which the contributions are made, as follows: • In Chapter2, after producing a catalogue of clusters for NGC 1566, fitting was required to give estimates of the ages and masses. Angela Adamo helpfully used her SED fitting code to provide these parameters for the project, for which I am grateful, as producing a successful code is difficult and time-consuming. Mark Gieles also provided his model for the behaviour of the luminosity function in different bands, so that we had a theoretical quantity to compare to our observations. In addition to this, a code was provided by Nate Bastian/Mark Gieles to fit the maximum likelihood of the mass function and provide the timescale for cluster disruption and the characteristic turnover mass of the observed Schechter function. • Contributions to Chapter3 include the full cluster catalogue for M 83, which was pro- duced and refined over several works, most notably Bastian et al.(2012) and Silva-Villa et al.(2014). Starting with a complete and reliable catalogue was invaluable to making the project quicker. Again, refitting the ages and masses of some clusters with different filter contributions was provided by Angela Adamo. • I would like to thank Carmela Lardo for help with the work in Chapter4. Without her knowledge of the methods for calculating abundances from line widths, effective temperatures and other parameters, the chapter and the publication would have been much slower. Contributions from all the above are discussed in more detail in their respective chapters. iv Besides the contributions from all these individuals, I would also like to thank Nate Bastian for being a great supervisor during my PhD and providing such interesting and rewarding projects. I’d also like to thank all the other PhD students during my time in the department, who helped make the experience a much more fun and lively one, especially Rob and the other D&D and boardgame players! Thanks for introducing us to Dominion and Agricola, amongst other games. I will never forget Sir Brian the Blessed, Clint of the Eastwood or that guy that tried to cut a branch from a tree with a sword and fell out, wherever he ended up. My parents also deserve thanks, as they have always been so encouraging no matter what I chose to study or do. However, I will subtract some percentage of these thanks to account for the nose that was provided to me. Finally, I would like to thank Elliott. Without your knack for distracting me with games or naps, I might have just gone and worked too hard, which would have been a real shame. v Publications The following papers are relevant to this thesis and have been published during the time this work was undertaken: 1. Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters Martocchia, S., Cabrera-Ziri, I., Lardo, C., Dalessandro, E., Bastian, N., Kozhurina- Platais, V., Usher, C., Niederhofer, F., Cordero, M., Geisler, D., Hollyhead, K., Kacharov, N., Larsen, S., Li, C., Mackey, D., Hilker, M., Mucciarelli, M., Platais, I., Salaris, M., 2017, arXiv:1710.00831 2. The search for multiple populations in Magellanic Cloud clusters - II. The detection of multiple populations in three intermediate-age SMC clusters Niederhofer, F., Bastian, N., Kozhurina-Platais, V., Larsen, S., Hollyhead, K., Lardo, C., Cabrera-Ziri, I., Kacharov, N., Platais, I., Salaris, M., Cordero, M., Dalessandro, E., Geisler, D., Hilker, M., Li, C., Mackey, D., Mucciarelli, A, 2017, MNRAS, 465, 4 3. The Search for Multiple Populations in Magellanic Cloud Clusters III: No evidence for Multiple Populations in the SMC cluster NGC 419 Martocchia, S., Bastian, N., Usher, C., Kozhurina-Platais, V., Niederhofer, F., Cabrera- Ziri, I., Dalessandro, E., Hollyhead, K., Kacharov, N., Lardo, C., Larsen, S., Muccia- relli, A., Platais, I., Salaris, M., Cordero, M., Geisler, D., Hilker, M., Li, C., Mackey, D, 2017, MNRAS, 468, 3150 4. Evidence for multiple populations in the intermediate age cluster Lindsay 1 in the SMC Hollyhead, K., Kacharov, N., Lardo, C., Bastian, N., Hilker, M., Rejkuba, M., Koch, A., Grebel, E. K., Georgiev, I., 2017, MNRAS Letters, 465, 1 vi 5. The Search for Multiple Populations in Magellanic Cloud Clusters I: Two Stellar Popu- lations in the Small Magellanic Cloud Globular Cluster NGC 121 Niederhofer, F., Bastian, N., Kozhurina-Platais, V., Larsen, S., Salaris, M., Dalessandro, E., Mucciarelli, A., Cabrera-Ziri, I., Cordero, M., Geisler, D., Hilker, M., Hollyhead, K.., Kacharov, N., Lardo, C., Li, C., Mackey, D., Platais, I., 2017, MNRAS, 464, 1 6. Properties of the cluster population of NGC 1566 and their implications Hollyhead, K., Adamo, A., Bastian, N., Gieles, M., Ryon, J. E., 2016, MNRAS, 460, 2087 7. Sizes and shapes of young star cluster light profiles in M83 Ryon, J. E., Bastian, N., Adamo, A., Konstantopoulos, I. S., Gallagher, J. S., Larsen, S., Hollyhead, K., Silva-Villa, E., Smith, L. J., 2015, MNRAS, 452, 525 8. Studying the YMC population of M83: how long clusters remain embedded, their inter- action with the ISM and implications for GC formation theories Hollyhead, K., Bastian, N., Adamo, A., Silva-Villa, E., Dale, J., Ryon, J. E., Gazak, Z., 2015, MNRAS, 449, 1106 9. Constraining globular cluster formation through studies of young massive clusters - V. ALMA observations of clusters in the Antennae Cabrera-Ziri, I., Bastian, N., Longmore, S. N., Brogan, C., Hollyhead, K., Larsen, S. S., Whitmore, B., Johnson, K., Chandar, R., Henshaw, J. D., Davies, B., Hibbard, J. E., 2015, MNRAS, 448, 2224 10. Constraining globular cluster formation through studies of young massive clusters - IV. Testing the fast rotating massive star scenario Bastian, N., Hollyhead, K., Cabrera-Ziri, I., 2014, MNRAS, 445, 378 11.
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