Star formation and Stellar Evolution
PhD Projects
Evolved stars in the UWISH2 Galactic Plane Survey
Tim Gledhill, Janet Drew, Dirk Froebrich (Kent)
The UWISH2 survey is the first wide-field imaging survey of the Galactic Plane (GP) in the 2.12 micron line of H2. The survey, to be completed in 2012, will provide a census of evolved stellar objects in the GP, especially those hitherto excluded from optical surveys by extinction due to dust. This project will: (i) identify and catalogue H2-emitting post-AGB and Planetary Nebula (PN) sources in the GP, cross-correlating with surveys at other wavelengths such as IPHAS (optical) Spitzer GLIMPSE (mid-infrared), CORNISH (radio); (ii) search for jet-powered outflows in H2 emission, similar to those seen in pre-main sequence stars; (iii) obtain follow-up imaging and spectroscopic observations at high resolution using facilities such as the VLT in Chile; (iv) investigate the shock physics of selected objects. The student will gain experience in optical and infrared imaging and integral field spectroscopy, wide-field survey exploitation, post-AGB and PN physics, H2 shock excitation and modelling.
Herschel and JCMT surveys of the Milky Way: understanding the formation of massive stars
Mark Thompson, Antonio Chrysostomou
The Herschel Space Observatory is currently undertaking a large survey of the inner Galaxy (Hi-GAL) with the aim of locating all the massive star-forming regions in the Galaxy. Longer wavelength counterparts to this survey are the JCMT Legacy Surveys JPS and SASSy. At UH we lead a number of the SCUBA-2 surveys, have recently completed a JCMT HARP survey of the Perseus Spiral Arm, and are playing significant roles in Hi-GAL and other surveys. Our aims with these projects are to understand the global properties of star formation in the Milky Way. One of the areas that we have begun working in is in combining the Herschel and SCUBA-2 data with extinction maps derived from optical and near-infrared surveys that are also led from Hertfordshire. We are particularly interested to recruit a PhD student to work in this cross-over area, to work on compiling a Galaxy-wide catalogue of Young Stellar Objects or on the evolution of dust within molecular clouds as they begin to form stars. This project will give you hands-on experience with some of the most cutting edge facilities in far-IR and sub-mm astronomy and also exposure to optical and near-infrared surveys.
Needles in a haystack of galaxies: Massive debris disks in the Herschel ATLAS
Mark Thompson, Dan Smith, Jason Stevens
The Herschel ATLAS is the largest area survey that the Herschel Space Observatory will undertake. The central aim of the survey is to identify potentially over a quarter of a million high redshift galaxies and understand their formation and evolution. However as a free byproduct Herschel ATLAS will also search over 10,000 nearby stars for the presence of debris disks - remnants of asteroid or Kuiper belts surrounding the stars. This search is much larger than other planned debris disk surveys (DUNES & SUNSS) by virtue of a completely different selection technique, meaning that Herschel ATLAS will be a powerful complementary and independent test of these studies. So far we have identified over 20 good candidate disks in the first data taken with Herschel. The project will involve identifying further debris disks in the ATLAS survey and studying their properties with follow-up Herschel PACS observations (we recently obtained time to follow up all of our candidates with PACS) and also with other facilities, including ALMA. You will be working as part of the international Herschel ATLAS team and will gain substantial experience in multi-wavelength astronomy from the far-IR and sub-mm to the infrared and optical.
Star formation in filaments
Antonio Chrysostomou, Mark Thompson
The star formation research group at the University of Hertfordshire are involved in and/or leading a number of surveys of the Milky Way in order to better understand how massive stars are formed. These surveys, undertaken with the Herschel Space Observatory and the James Clerk Maxwell Telescope (JCMT), have been specifically designed for this purpose. Even though massive stars are relatively small in number, they dominate the energy, dynamical and chemical evolution of our Galaxy and, in fact, all other galaxies in the universe. Despite this, their formation and evolution are poorly understood. A recent and important discovery from the Herschel survey of the Galactic Plane (Hi-GAL) is that significant star formation occurs in filamentary structures that appear to permeate our Galaxy, a fact that we are only now beginning to realise. A student working on this project will do so with data from both the JCMT and HiGAL to identify the presence of filaments in the Galaxy, understand the properties of cores, clumps and stars forming within those filaments and determine any difference between star formation within and without filaments. The student will be working with a large team of international astronomers, and be expected to lead this particular research stream.
Improving models of massive stars
Thomas Rauscher, R. Hirschi (Keele), Sean Ryan
Understanding the origin of the elements and the production of nuclides throughout the Galactic history in various astrophysical sites is one of the most exciting questions in physics. It requires interdisciplinary research combining the fields of astrophysics, astronomy, nuclear and particle physics. In this context we are offering a PhD project with emphasis on astrophysical modelling of hydrostatic and explosive phases of stellar evolution. The student will work with state-of-the-art stellar models, trying to improve spherically symmetric simulations through new insights gained from 3-D hydrodynamics, and study the effects on nucleosynthesis. Comparison to observational data further constrains the models. At the same time, variations in the patterns of produced nuclei stemming from uncertainties in the nuclear input will be explored. An estimate of general uncertainties in the rates of reactions as employed in astrophysical simulations will be derived and applied in computation-heavy Monte Carlo variation studies to systematically quantify, for the first time, the main sensitivities of massive star nucleosynthesis. The results will allow to prioritize further improvements in the astrophysical and nuclear models in close collaboration with international groups. Depending on the project progress, the student will also be directly involved in this extension.
Astrophysical reaction rates for heavy element nucleosynthesis
Thomas Rauscher, Chiaki Kobayashi, C. Fröhlich (NCSU, USA)
Understanding the origin of the elements and the production of nuclides throughout the Galactic history in various astrophysical sites is among the most exciting questions in physics. In this context we are offering a project with emphasis on modelling nuclear reactions in stellar and explosive environments. Astrophysical reaction rates are key quantities to understand nucleosynthesis. Nuclear reactions proceed differently in astrophysical plasmas than in the laboratory and additional effects have to be considered. The majority of isotopes created in explosive nucleosynthesis is very short-lived and cannot be studied experimentally at all. Model predictions of nuclear reactions are therefore essential. The project involves the implementation of previously unconsidered effects and improved knowledge of nuclear properties into existing reaction models, and to test the new predictions in comparison with the scarce experimental data. The impact of the results on production of nuclei in various astrophysical environments - stars, supernovae, explosive nuclear burning on the surface of a neutron star - will be studied in post-processing reaction networks. In order to obtain a larger picture of the global impact, this will be tied to Galactic Chemical Evolution models to investigate their sensitivity to uncertainties in the knowledge of fundamental nuclear properties.