Thesis Topic: The interplay of massive stars, gas and dust in very nearby starbursts
Thesis Supervisor: Jeremy R. Walsh
The complex interplay between regions of massive star formation and their surroundings is a determining component of galaxy evolution. Winds of massive stars and the resulting supernova explosions inject mechanical energy into the interstellar medium, redistributing gas within a galaxy. The ejected nuclear processed products affect the chemical enrichment of the galaxy. Conversely changes in the conditions of the gas within a galaxy, such as re-distribution due to an interaction with a companion galaxy, can trigger the formation of new stars or quench the existing star formation. The ideal environment to learn about these processes is presented by very nearby starbursts and giant HII regions where high spatial resolution and sensitivity can be achieved. Understanding the details of these processes in nearby targets provides a template for interpreting observations at higher luminosity and redshift, relevant to the earliest stages of galaxy formation.
A PhD project is proposed aimed at better understanding the details of the starburst phenomenon and the interactions occurring in this decisive stage of galaxy evolution. The "stars -> gas" interaction will be attacked from two fronts:
- Observational: Existing Integral-Field Spectroscopy (IFS) data of nearby starburst galaxies, such as NGC 5408 (see image), as well as high resolution HST imaging, will be reduced and analysed. The massive star population (i.e. number and type of stars, age, location, etc.), and the physical (i.e. electron density and temperature, kinematics, excitation) and chemical (i.e. metallicity and relative abundances) properties of the ionized gas, will be mapped.
- Modelling: Photoionization modelling, using the CLOUDY code, will be employed to reproduce the 2D properties of the interstellar medium from the ingredients of ionizing stars and neutral and ionized gas. Modelling allows the prediction of quantities not included in the original data set, such as emission lines at other wavelengths (e.g. in the mid-infrared) which open up further observational opportunities.
In developing the observational and modelling tools and tackling these questions, further avenues can be developed and will be encouraged in the course of the project. The most relevant is the interaction "gas -> stars" in the form of observations of neutral and molecular clouds and star-forming regions with facilities such as ALMA.
NGC 5408 HST WF/PC2 composite u,b,v,Hα,r image from Steve Byrne's Astroimages