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Super Star Cluster Formation, Effects, and Evolution in CO with ALMA

  • Author(s): Consiglio, Santina Michelle
  • Advisor(s): Turner, Jean L
  • et al.

Super star clusters (SSCs) are important sources of energy, ionizing photons, and metals in galaxies. With masses of 100,000-1,000,000 M⊙, SSCs have the mass necessary to create O and B stars as well as to form globular clusters. Despite their overall importance, little is known about how SSCs form, evolve, and affect their environments. In my thesis, I use submillimeter tracers of gas and its kinematics from the newly commissioned Atacama Large (Sub)Millimeter Array (ALMA) as well as the Submillimeter Array (SMA) to study SSCs, their associated gas and dust and feedback from young stars in two local dwarf galaxies, NGC 5253 and II Zw 40. In II Zw 40, we find a low gas-to-dust ratio (GTD) of ~70 in a cloud near a SSC, whereas we find GTD>270 in an isolated cloud with no associated star formation <200 pc to the east, as expected in this low metallicity galaxy. We propose that the SSC has polluted its natal cloud with dust and metals. In NGC 5253, we find gas filaments that appear to be connected to the well-known HI filaments surrounding this galaxy. Infalling filaments could fuel the star formation, leading to the creation of SSCs. In NGC 5253 we also detect unusual optically thin 12CO(3–2) emission in two clouds with the embedded SSCs; we propose that the gas is thin because it is hot. Thus, we conclude that 12CO(3–2) emission alone is a poor tracer of gas mass; instead clouds could appear bright because they are hot. A comparison between older, visible star clusters and our CO(3–2) observations of young, dense, star-forming gas clumps in NGC 5253 suggest a new generation of star formation in this well-known starburst galaxy. We find that over all, the star-forming clumps emitting CO(3–2) do not correspond to known clusters, which is probably an age effect. In NGC 5253, we also find low GTDs in the central Cloud D region, particularly in Cloud D1, the cloud associated with the supernebula. We suggest that the massive clusters have locally polluted their environment. Cloud D1 has a narrow CO linewidth and no evidence of a cluster-scale outflow, we suggest that the dust pollution from the massive stars has stalled the cluster wind. Further investigation is needed as the dust fluxes are highly uncertain. Both II Zw 40 and NGC 5253 show evidence of star- forming filaments that separate into dense clumps, suggesting a common filamentary formation process for SSCs. Combined, the results from my thesis offer new insights into the importance of environments for the formation of SSCs – in the effects of SSCs polluting their local environments with dust, as well as the possibility that they may preferentially be formed by the process of cold stream accretion.

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