I am a Lecturer and Royal Society Research Fellow
in the Cosmology
subgroup of the Astrophysics
Group of the Department of
Physics and
Astronomy at University College
London .
I currently focus mostly on extracting information about cosmology using weak gravitational lensing. I think this is the most beautiful image of strong gravitational lensing:
Weak gravitational lensing is the subtle distortion of the images of distant galaxies due to intervening matter. The distortion is so small that it is not possible to tell if a single galaxy has been affected. But if galaxies are assumed to be randomly oriented on the sky, then averaging over many galaxies uncovers alignments of galaxies due to gravitational lensing.
Currently the biggest puzzle in cosmology is the nature of the dark energy which seems to make up 70 per cent of the universe and cause accelerated expansion of the universe. Weak gravitational lensing can tell us about the dark energy because it shows us the dark matter distribution. The dark matter clumps less with time if there is more dark energy, since the dark energy is stretching the universe out and counteracting the attraction by gravity. Also the apparent angular size of dark matter structures is larger the more dark energy there is.
It seems to me that compared to other cosmological probes, gravitational lensing has the greatest potential for telling us more about the dark energy. However there are a number of areas which require more work so that the full potential can be reached, and I am concentrating on the following:
To find out more you could read my lectures and links therein.
I currently focus mostly on extracting information about cosmology using weak gravitational lensing. I think this is the most beautiful image of strong gravitational lensing:
Weak gravitational lensing is the subtle distortion of the images of distant galaxies due to intervening matter. The distortion is so small that it is not possible to tell if a single galaxy has been affected. But if galaxies are assumed to be randomly oriented on the sky, then averaging over many galaxies uncovers alignments of galaxies due to gravitational lensing.
Currently the biggest puzzle in cosmology is the nature of the dark energy which seems to make up 70 per cent of the universe and cause accelerated expansion of the universe. Weak gravitational lensing can tell us about the dark energy because it shows us the dark matter distribution. The dark matter clumps less with time if there is more dark energy, since the dark energy is stretching the universe out and counteracting the attraction by gravity. Also the apparent angular size of dark matter structures is larger the more dark energy there is.
It seems to me that compared to other cosmological probes, gravitational lensing has the greatest potential for telling us more about the dark energy. However there are a number of areas which require more work so that the full potential can be reached, and I am concentrating on the following:
- Removal of contaminating image distortions by the telescope and atmosphere.
- If galaxies are not randomly oriented in the sky this will contaminate the signal if not taken into account.
- To obtain distances to the lensed galaxies for a large survey "photometric redshifts" must be used, and their limitations carefully taken into account.
- The gravitational lensing signal is determined only on averaging over many millions of galaxies but the optimal statistics have not yet been developed to extract the maximum information.
To find out more you could read my lectures and links therein.