Search Herts

Star formation and Stellar Evolution

  • Massive Star Formation in the outer reaches of the Milky Way

    Mark Thompson, Jan Forbrich

    Most surveys of our Milky Way galaxy are focused on the inner third of the Milky Way's disk as this is the most cost effective way to search the volume of the Milky Way for massive star formation. The "outer reaches" of the Milky Way located outside the Sun's orbit have not been well-studied due to the larger areas of sky that need to be mapped and the lower density of star forming regions there. However, this neglects the importance of the low metallicity regions in the Outer Galaxy as potential analogues for star formation in the earlier Universe. In this project you will take advantage of two recent sub-millimetre surveys (SASSy and SASSy-Perseus) to create a definitive atlas of the star formation  in the outer reaches of the Milky Way. You will use archival molecular spectroscopy to determine the distance to these regions, search for signs of embedded star formation using the JVLA telescope and archival data, and determine the star formation rate for these regions. This will create a valuable dataset with which to compare to the ATLASGAL studies of the inner Milky Way (Urquhart et al 2018) and resolved  studies of nearby galaxies (e.g. M31, Forbrich et al 2020). Our eventual aim is to determine a physical relationship between the properties of molecular gas and the resulting massive star formation, which can then be used to interpret unresolved high redshift studies.

  • Cloud-scale star formation laws in the Andromeda Galaxy: the role of metallicity

    Jan Forbrich, Dan Smith, Mark Thompson

    Star formation plays a critical role in both galaxy and cosmic evolution. Indeed, it is the rate of star formation that is the primary metric for cosmic evolution studies. Within galaxies star formation occurs in giant molecular clouds (GMCs). The physical conditions within these clouds set the star formation rate (SFR). The interplay between observable properties of the interstellar medium and the SFR is often described by empirical star formation 'laws'. We are presently conducting a large-scale project to study cloud-scale star formation laws in the Andromeda Galaxy, involving the Submillimeter Array (SMA) for novel, resolved dust continuum observations of individual GMCs (see Forbrich et al. 2020 for first results) and the Very Large Array (VLA) to survey all 326 known cloud complexes for HII regions. In this project, you would work on a third pillar of this project, which consists of multi-object optical spectroscopy of the HII region candidates identified with the VLA, again targeting all 326 known cloud complexes. We are conducting these observations with Hectospec on the 6.5m MMT. You would work on several aspects of the data reduction within our collaboration to then pursue a range of science goals: 1) confirm the identification of radio sources as HII regions and identify contaminants, 2) measure their individual metallicities, improving on previous measurements of metallicity gradients in M31, and 3) test extinction corrections by comparing H-alpha and associated SFR metrics with the extinction-free centimeter radio flux. This project will produce a large sample of HII regions with detailed properties in the context of their cloud complex environments. In particular, it will enable a detailed assessment of metallicity on the star formation properties of individual clouds. It will additionally inform the continuing observations for this project, most importantly those with the SMA, such that there is an opportunity to shape this continuing experiment. Your research work would be conducted in an international, novel and ongoing multi-wavelength project, involving, if conditions allow, observing visits to world-class observing facilities.