Jak Kelly Award lecture and Christmas party

“Hydroxyl as a probe of the molecular interstellar medium”

  Anita Petzler, Jak Kelly Award winner for 2018

  Department of Physics and Astronomy
  Macquarie University

Wednesday 5 December 2018
State Library of NSW, Sydney

The Jak Kelly Award
This award was created in honour of Professor Jak Kelly (1928 – 2012), who was Head of Physics at University of NSW from 1985 to 1989, was made an Honorary Professor of University of Sydney in 2004, and was President of the Royal Society of NSW in 2005 and 2006.  Its purpose is to encourage excellence in postgraduate research in Physics.
The winner was selected from a short list of candidates who made presentations at a recent joint meeting of the Australian Institute of Physics NSW Branch, the Royal Australian Chemical Institute and the Royal Society of NSW, which was held at UNSW.

Abstract
The interstellar medium is the collection of gas and dust between the stars of a galaxy and is the raw material from which new stars are formed. Its physical properties as well as a complex set of internal and external influences determine the mass distribution of stars formed. By observing the interstellar medium, we can begin to unravel these complex interactions and build robust models of star formation in galaxies. The interstellar medium consists of atomic gas traced by 1420 MHz hydrogen emission, and molecular gas traditionally traced by 115 GHz carbon monoxide emission.
My research recognises the limitations of carbon monoxide as a tracer of more diffuse molecular gas and employs an alternate tracer: hydroxyl. Hydroxyl is expected to coexist with molecular hydrogen in all environments, including those not well traced by carbon monoxide. The ground state of hydroxyl is split into four levels due to lambda doubling and hyperfine splitting. There are four allowable transitions between those levels at 1612, 1665, 1667 and 1720 MHz. The relative population of hydroxyl molecules in each level is determined by the local gas conditions which in turn determines the relative intensity of absorption or emission. I measure the emission and absorption in the transitions of hydroxyl along sightlines towards bright background continuum sources to determine the local conditions of the intervening hydroxyl gas. Modern observation techniques including large-scale surveys using telescopes with unprecedented resolution such as the Square Kilometre Array will give us an overwhelming wealth of data. Therefore, I am developing an automated analysis pipeline that will allow us to quickly extract our target parameters from these observations in a physically and statistically rigorous way. My work will allow us to take full advantage of these remarkable new facilities to complete our understanding of the mechanisms of star formation.

Biography
After growing up in Southern California, Anita Petzler moved to Australia at the age of 18 to complete a Bachelor of Science in Physics and Astrophysics at Monash University in Melbourne. This was followed by a Graduate Diploma of Education, an 8-year career as a High School Physics and Science teacher, and a move to Sydney. She returned to her studies in 2013, completing Honours at UNSW with a project on molecular clouds of the interstellar medium, supervised by Dr Maria Cunningham. Her interest in this field continued with a Masters by Research at Macquarie University supervised by Dr Joanne Dawson. She then began a PhD in July of this year under the supervision of Dr Joanne Dawson and Dr Mark Wardle.
“Ever since the age of 5, when my kindergarten teacher introduced me to the science of space, I’ve known that I wanted to be an astronomer. It’s been a long journey, but the completion of my PhD will represent the realisation of the dreams of that little 5-year-old girl. Thank you for the opportunity to share my enthusiasm and interest in this grand field with such a distinguished group of like-minded scientists.”

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