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Over the last few decades large scale surveys (e.g. SDSS and GAMA) have transformed the way we understand how galaxies form and evolve. One of the key observables needed for studying galaxies is their star formation rate. This can be estimated from multi-wavelength methods, from UV to optical spectral lines (e.g. H-alpha) to infrared emission.

Radio emission can also trace the star formation rate of a galaxy, and has the advantage that it is not blocked by dust (unlike UV or optical light). Radio continuum emission (at 1.4 GHz) in normal galaxies is produced by electrons accelerated by supernova, and since supernova happen when stars die the radio continuum emission is thought to be related to star formation. The tight correlation between radio continuum emission (at 1.4 GHz) and dust emission, which is also heated by stars, is evidence that it is radio emission related to star formation. However a more direct tracer of SF emission in the radio may come from HII (or star forming) regions within a galaxy. This type of emission is dominant at higher radio frequencies (~10 GHz).

GLASS, the GAMA Legacy ATCA Southern Survey, is a ATCA legacy survey project that has been allocated 3000 hours over six semesters. Our goal is to the full 50 square degrees of the G23 GAMA field at 5.5 and 9.5 GHz with the ATCA to 10s microJy/beam depths, the deepest ever survey over such a large area. We expect to detect about 2,000 nearby normal galaxies and with the excellent multi-wavelength (UV to infrared) and spectroscopic coverage we will have multiple estimates of the star formation rate in the galaxies. Using the higher frequency 5.5 and 9.5 GHz data with lower frequency data from ASKAP and MWA, this PhD project aims to calibrate the radio star formation rate (which is important for future work with SKA) and decompose the radio emission into that from supernova acceleration vs HII regions, thus potentially obtaining a more reliable measure of galaxy star formation rates.

The first semester of GLASS observations are now complete. The student will have the opportunity to learn radio interferometry, perform observations, and do data analysis in a very hands on fashion, which is not possible in the future with remote facilities such as ASKAP and SKA. Collaboration and travel opportunities exist with many domestic and international scientists, including astronomers based in Croatia, Italy, United Kingdom, India and the United States.

Galaxy M82 is an example of a local galaxy under going a burst of star formation. This project will examine similar galaxies in the GLASS survey, using high frequency radio wavelengths to characterise their star formation. Image Credit: NASA, ESA, The Hubble Heritage Team, (STScI/AURA).

 

The spectrum of M82, from Condon 1992. The solid line shows sum of synchrotron or supernovae-induced radio emission (dot-dash line) , HII or free-free radio emission (dashed line), and dust blackbody emission (dotted line). The GLASS project aims to use HII radio emission to better understand and measure star formation in these galaxies.

Co-Supervisors

Professor Lister Staveley-Smith

Director, Science (UWA)

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Dr Nick Seymour

Senior Lecturer

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Dr Luke Davies

WAVES Project Scientist

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