wide-field sky surveys, object classification and photometric redshift estimation

growth of supermassive black holes, early universe and varaibility

optical counterparts to gravitational-wave events

galaxy evolution through cosmic epochs and via environmental influence

dust in the Milky Way and star-forming galaxies

Jan 1999:  PhD at Max-Planck-Institute of Astronomy Heidelberg, Germany

until 2001: Research Fellow at MPIA Heidelberg, PI of COMBO-17 survey

2001-2013: University of Oxford, UK (2004-2009 STFC Advanced Fellow)

from 2013: RSAA Mt Stromlo, ANU, Canberra, Australia

2016-2018: ANU Node Leader of CAASTRO (ARC Centre of Excellence in All-sky Astrophysics)

Ultra-luminous quasars and the growth of the most massive black holes in the early universe:

We use the SkyMapper Southern Survey together data from the Gaia and WISE satellites to identify the most luminous quasars in the early universe. Then we measure the masses of their black holes and investgate how fast early black holes are growing. Are they slowly growing from seeds that are more massive than we can explain? Or are the growing faster than the Eddington accretion llimit instead?

Classification in the SkyMapper Southern Survey

The SkyMapper Southern Survey will contain photometry for a billion objects in its next data release, which can be stars, galaxies, quasars, asteroids and artefacts. We have training sets for these and external information from astrometry and multi-wavelength missions. Using all the available information we can statistically classify every object in the survey, and using photometric redshifts we can estimate their distance without taking a spectrum. 

Search for kilonovae from neutron-star collisions 

SkyMapper is switched into an alert override mode as soon as gravitational waves from a merger event are recorded with LIGO/Virgo. We rapidly identify optical transients with SkyMapper and investigate them further. Which one is the kilonova from the collision and what does it tell us? Only one kilonova has been seen so far, in 2017. The next could be just around the corner.

Variability of quasar accretion disks

Using long-term light curves for thousands of quasars we study the variable luminosity of the accretion disks around their supermassive black holes. This can tell us about their sizes and temperature profiles, which are mostly unknown so far.

We also search for supermassive black holes whose accretion is only episodic and switches on and off on a timescale of years. These "changing-look AGN" are discovered more and more, but what is their distribution and what might cause their nature?

Strong flares from stars and other rare transients

With SkyMapper and other telescopes we monitor the sky for strong outbursts of light from stars and other unexplained bright transients. Are any of them visible to the naked eye, even though they originate from far away?