Speaker
Description
Roughly one in a thousand quasars or bright galaxies at cosmological distances appears to us as a multiple-image mirage, caused by gravitational lensing by an intervening galaxy or cluster. The separation between the multiple images ranges from sub-arcsecond to tens of arcseconds, which is easily resolved by standard telescopes. These are sometimes called macro-images.
Each macro-image actually consists of a swarm of micro-images on the micro-arcsecond scale. The micro-image swarm is produced by the small-scale variations (due to stars) in the gravitational field of the lensing galaxy or cluster. The micro-image swarm is time-varying because of the motion of stars, and it is thought that micro-images appear and disappear on time scales of months. A micro-image swarm has never been resolved, only the resulting brightness variation of macro-images has been observed. Resolution of micro-image swarms would be a novel statistical probe of the stellar mass function.
In this presentation we will explain all the above, and then argue that resolving the brightest micro-image swarms will be within the reach of a future VLT-ELT intensity interferometer with instruments now in development (100s of wavelength channels at 10ps time resolution).
