The Implementation Plan:
The first four cluster/blank field pairs will be observed with Director's Discretionary time in Cycles 21 and 22. The observations of the final two cluster/blank field pairs in Cycle 23 will be contingent on the initial results from Cycle 21/22. HST will obtain WFC3/IR and ACS images simultaneously for each cluster/parallel blank field at a fixed position angle, and then swap camera positions roughly 6 months later.
The program devotes 140 orbits to each cluster/blank field pair, achieving AB ≈ 28.7-29 mag optical (ACS) and NIR (WFC3) imaging with 560 orbits in Cycles 21/22. Limiting AB mags are for 5-sigma detections of a point source within a 0.4" diameter aperture.
|ACS: (70 orbits per position)||WFC3/IR: (70 orbits per position)|
Six Frontier Fields:
|Cluster Name||z||Cluster||Parallel Field||HST
|Abell S1063 (RXCJ2248.7-4431)||0.348||22:48:44.4||-44:31:48.5||22:49:17.7||-44:32:43.8||regions|
These were selected primarily on their predicted lensing strength*, their low/moderate zodiacal and Galactic backgrounds, their observability with ALMA and Mauna Kea, and their observability with HST and Spitzer. We've also looked at their suitability for deep radio observations, and their existing multi-wavelength data observations.
(* Lensing strengths were calculated by Dan Coe, Johan Richard, and Adi Zitrin, based on existing HST data.)
The parallel blank field positions are constrained by the availability of HST guide stars, which permit > 30-day windows of fixed roll-angle observations with both ACS and WFC3 at both the cluster and blank field positions. From the available locations, the final parallel field location was based primarily upon the ability to obtain very deep, high quality imaging in both HST and Spitzer. Therefore the avoidance of bright stars which would cause scattered light, saturated columns, and persistence took precedence over the avoidance of extended cluster structures.Cluster Candidate List