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Philip Lah's Research

Research

PhD Thesis (PDF)

Refereed Publications

Nonrefereed Publications

Research Interests:

The evolution of stars and gas in galaxies. Observing the atomic neutral hydrogen (HI) 21 cm emission and radio continuum emission of galaxies. Analysing optical spectra from galaxies in order to determine their star formation history, age and metallicity.

The Evolution Gas in Galaxies

Collaborators:
Frank Briggs, Jayaram Chengalur, Matthew Colless, Mike Pracy and Roberto De Propris

The goal of research is to quantify the neutral atomic hydrogen (HI) gas content galaxies as they evolve with time. The amount of star formation in galaxies is observed to have been much higher in the past, reaching a factor of ten times higher 8 billion years ago. However the amount of neutral atomic hydrogen gas (the fuel for star formation) in galaxies is only poorly constrained over this time period.

Neutral atomic hydrogen gas produces a radio signal that can be used to directly measure the amount of gas present. This radio signal from galaxies in the distant past is only now reaching us but it is quite weak due to the large distances involved. This makes this signal difficult to detect even with the largest radio telescopes available today. However, using optical observations of the position and redshift of a galaxy, we can identify were we expect the weak radio signal from the gas to be in radio observations of that galaxy. The combination of these signals from multiple galaxies is strong enough to measure, allowing us to quantify the total amount of atomic neutral hydrogen gas in these distant galaxies.

The radio observations for this project come from the Giant Metrewave Radio Telescope (GMRT) in India. Optical observations come from numerous sources including the Subaru Telescope and Anglo-Australian Telescope.

This work was part of my PhD thesis and has continued into my postdoctoral research.

Previous Research

Red Giant Variables in the Large Magellanic Cloud

School of Physics Vacation Scholarship, University of Sydney (Summer 2003-2004)

Supervisor: Tim Bedding and further work with Laszlo Kiss

USyd Summer Research Scholarship Report (PDF)

Link to Paper: Red variables in the OGLE-II data base - III. Constraints on the three-dimensional structures of the Large and Small Magellanic Clouds

Exploring the Stellar Population of Early-Type Galaxies
in the 6dF Galaxy Survey

Honours Thesis (2003)

Supervisors: Matthew Colless and Heath Jones

Honours Thesis (PDF)

Variable Stars and Extra-Solar Planets in Globular Cluster 47 Tucanae

RSAA Summer Research Scholarship (Summer 2002-2003)

Supervisors: David Weldrake and Penny Sackett

RSAA Summer Research Scholarship Report (PDF)

74" Telescope Efficiency Response

Research Topic in Physics (1st Semester 2002 BSc Unit)

Supervisor: Paul J. Francis

Research Topic Write Up (PDF)

Last modified: June 2013