My cosmology research uses strong gravitational lensing to study black holes, dark matter and distant galaxies.
Imagine two galaxies aligned along our line of sight. The gravity of the foreground galaxy bends light from the background galaxy, allowing it to reach Earth along multiple paths.
Here is a simple 2D schematic of a strong gravitational lens:
Image credit: F. Courbin, S. G. Djorgovski, G. Meylan et al., Caltech / EPFL / WMKO (source).
The Most Massive Black Holes:
In some cases, lensed light passes close to a massive black hole at the centre of the foreground galaxy. Using this technique, I discovered a black hole with a mass 33 billion times that of the Sun.
You can see the incredible results in this video:
I was interviewed about this discovery on BBC Four’s The Sky at Night:
View the episode on the BBC website.
The Smallest Dark Matter Clumps:
Gravitational lensing can also reveal dark matter. Models predict small clumps of dark matter that disturb lensed light as it passes nearby.
In a recent study using images captured by the Hubble Space Telescope, I investigated one such gravitational lens, known as SDSSJ0946+1006, shown below:
My analysis produced a dark matter map, with possible clump locations shown in green. I found a clump with a mass of around one billion solar masses.
Discoveries like this help us understand how dark matter is distributed in galaxies.
Revealing the Most Distant Galaxies:
Gravitational lenses act as cosmic telescopes: they magnify the light of distant galaxies, making those galaxies appear brighter and revealing details we could not otherwise see.
This Hubble Space Telescope image shows the strong gravitational lens SDSSJ1430-4150. A foreground galaxy sits at the centre, surrounded by a nearly complete ring of light from a more distant galaxy.
Using gravitational lens analysis software I developed, we reconstructed the distant galaxy’s appearance before its light was lensed. The result below reveals a grand-design spiral galaxy.
PyAutoLens:
The analyses above use PyAutoLens, the open-source software I lead development of.
I want to make strong lensing accessible to more people. The HowToLens lectures teach the science of lensing and how to analyse real astronomy data through interactive Jupyter notebooks.
PyAutoLens Links:
Code: PyAutoLens on GitHub
Documentation: PyAutoLens documentation
Software paper: PyAutoLens in the Journal of Open Source Software
Try PyAutoLens: Open the start_here notebook in Google Colab to explore PyAutoLens in your browser.
Science Papers: