I am involved in the lens mapping of the cluster for the HST Frontier Fields campaign during Cycle 21-23. This program is essentially the Hubble Deep Field on steroids -- HST will stare at massive clusters and parallel fields for 140 orbits each with WFC3/IR and ACS and use the magnification boost from lensing to study the faint end of the galaxy luminosity function at z>7 and find super high-redshift galaxies (z>10), the ancestors of the most massive galaxies we see today.
During the summer of 2013, I modeled the lensing in each of the six Frontier Fields clusters from preliminary HST data and ground-based supplementary data. The magnification maps and lens models for all the clusters are now publicly available.
We are also using our resources at Michigan (Magellan telescopes) to spectroscopically confirm and measure the redshifts of lensed sources and cluster member galaxies in these fields to improve upon future revisions to these lens models.
The Frontier Fields, based on their wealth of lensing constraints and follow-up data, are an excellent opportunity to test lens modeling systematics. We are beginning to investigate the systematic errors that can occur in our lens modeling methods, specifically when the redshifts of the lensed galaxies are unknown. We find that the magnification values are inconsistent between models with different assumptions about the redshifts of the background galaxies.
I also plan to stay involved in model revisions and will keep the public models up-to-date as more data become available.
Papers
- Frontier Fields lens models: Johnson et al., (2014) - Line of sight structure: Bayliss et al., (2014) - Cosmological parameter uncertainies and lens models: Bayliss et al. (2015) - Time delays of Supernova Refsdal: Sharon & Johnson (2015) - Refsdal meets Popper -- time delay challenge: Treu et al. (2015)