Image Credit: ESO/M. Kornmesser

What do we do?

Our research focuses on the study of the intergalactic medium using quasar spectroscopy. This field of research is commonly known as observational cosmology and consists of studying the origin, structure and evolution of the Universe through astronomical observations.

What is quasar spectroscopy?

Quasars are among the brightest and most distant objects in the Universe. When a photon produced by a distant quasar reaches a telescope on Earth, it carries with it all the information from the part of the Universe it crossed. This information can be identified and extracted by fitting the absorption features imprinted onto the quasar spectrum.

What knowledge can you get?

Any absorption line in a quasar spectrum is a direct signature of a gas cloud present in the intergalatic medium and can be approximated by a mathematical function called a Voigt profile. From such profile, one can gain insight into the kinematics of the atoms in the cloud as well as the local temperature and density of atoms present in that cloud.

How do we use this information?

The knowledge we get from fitting absorption line features can be used to probe the evolution of the fundamental laws of physics throughout the Universe, that is throughout cosmological time from the Big Bang until now. In the next section, we present our 3 main projects.


Primordial Deuterium abundance

Deuterium is the second lightest element in the Universe and was produced during the very first minutes after the Big Bang in the epoch known as Big Bang Nucleosynthesis (BBN). The current standard BBN theory predicts that the primordial abundances of very light nuclei can be directly related to the mean cosmological baryon density parameter. The Deuterium-to-Hydrogen ratio can be directly measured in quasar spectrum by identifying and fitting both HI and DI absorption lines. The ratio of the extracted column densities will provide a direct estimate of the total density of baryonic matter in the Universe.

"The primordial deuterium abundance at z=2.504 from a high signal-to-noise spectrum of Q1009+2956", E. O. Zavarygin et al.

Fine-structure constant variation

Short description missing.

"Probing the Gravitational Dependence of the Fine-Structure Constant from Observations of White Dwarf Stars", M. B. Bainbridge et al.

Long-range wavelength-scale distortions

Short description missing.

"Modelling long-range wavelength distortions in quasar absorption echelle spectra", V. Dumont & J. K. Webb

Our Group

Prof. John K. Webb

Astrophysics Professor
@ University of New South Wales
@ DAMTP, Cambridge University

Dr. Vincent Dumont

Research Associate
@ UC Berkeley
@ University of New South Wales

Dr. Signe R. Sørensen

Research Associate
@ University of Oslo

Mr. Evgeny Zavarygin

PhD Student
@ University of New South Wales

Ms. Michael Wilczynska

PhD Student
@ University of New South Wales

Mr. Darren Dougan

PhD Student
@ University of New South Wales


Dr. Matthew Bainbridge

Research Associate
@ University of Leicester

Mr. Dinko Milaković

PhD Student
@ European Southern Observatory

Prof. Victor Flambaum

Physics Professor
@ University of New South Wales
@ Helmholtz Institute Mainz

Transparent Research

Get in touch

Feel free to contact us if you are either interested to join our group or simply want to know more about our research.

+1 (808) 498-8047

275 Birge Hall
University of California, Berkeley