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High-resolution studies of massive young stellar objects in the Magellanic Clouds

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Abstract

This thesis presents sub-arcsecond resolution observations of massive Young Stellar Objects (YSOs) in two satellite galaxies of the Milky Way, the Magellanic Clouds. With metallicities of »0.5 and »0.2 Z¯ for the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC), respectively the Magellanic Clouds present a unique opportunity to study star formation in environments which differ significantly from those of our own Galaxy.

19 targets in the SMC and 3 targets in the Hii region LHA 120-N113 in the LMC were observed with the near-infrared integral field spectrograph SINFONI at the VLT. Archival SINFONI data towards 7 targets in the Tarantula nebula in the LMC were also obtained. These observations reveal a wide variety of spatially extended emission line morphologies, indicative of outflows and compact Hii regions. Additionally, the most direct indications to date for the presence of discs in massive YSOs in the Magellanic Clouds are presented.

Previously obtained optical spectra towards massive YSOs in the SMC have been analysed, as well as newly obtained spectra using the Robert Stobie Spectrograph (RSS) at the Southern African Large Telescope (SALT). Fabry-Perot interferometric observations obtained with RSS at SALT towards two star forming Hii regions in the Magellanic Clouds, are also presented, along with a new Fabry-Perot data reduction pipeline. Through analysis of the optical spectra in the context of the SINFONI data the massive YSOs in the SMC appear to reside in a porous ISM, allowing a large mean-free-path for energetic photons.

Through a comparison of massive YSOs in the Magellanic Clouds and a previously obtained Galactic sample, evidence of significantly enhanced accretion rates towards the YSOs in the Magellanic Clouds is detected. Whilst the underlying mechanism of this enhancement is uncertain, there appears to be a convincing correlation between metallicity and accretion rates in massive YSOs.

Citation

(2017). High-resolution studies of massive young stellar objects in the Magellanic Clouds

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