Letters of Intent for 2015

LoI 2015-173
Focus Meeting: Pushing the Frontiers of Cosmology and Galaxy Formation with HST

Date: 3 August 2015 to 14 August 2015
Location: Honolulu, United States
Contact: Harald Ebeling (ebeling@ifa.hawaii.edu)
Coordinating division: Division J Galaxies and Cosmology
Co-Chairs of SOC: Harald Ebeling (IfA, University of Hawaii)
Jean-Paul Kneib (EPF Lausanne)
Masamune Oguri (University of Tokyo)
Tommaso Treu (UC Santa Barbara)
Priyamvada (Natarajan)
Co-Chairs of LOC: Harald Ebeling (IfA, University of Hawaii)
Nicholas Kaiser (IfA, University of Hawaii)
William Burgett (IfA, University of Hawaii)



Properties of gravitationally lensed galaxies at high redshift

Properties of the galaxy population of the HFF clusters

The mass distribution and internal dynamics of massive clusters

Modelling techniques based on strong and weak gravitational lensing

Ground- and spacebased follow-up studies of the HFF

Transient sources in the HFF

The significance of the HFF for future studies with JWST and 30m-class telescopes



In the course of the past few decades, gravitational lensing has proven to be an exceptionally powerful tool for studies of faint objects at the edge of the observable Universe, as well as for the characterization of the mass distribution in the lensing system. Generating significant gravitational amplification over areas of several square arcmin, massive galaxy clusters in particular are natural telescopes that allow us to probe the distant universe to unprecedented depth.

Progress made in recent years has provided us with a unique opportunity to fully exploit the potential of clusters as gravitational telescopes. For one, all-sky surveys designed specifically to find the most massive galaxy clusters have unveiled previously unknown and extremely powerful cluster lenses. In addition, coordinated efforts within the extragalactic community have led to parametric and non-parametric lens modeling techniques that combine the strong- and weak-gravitational lensing signal and are capable of creating highly accurate descriptions and calibrations of lensing clusters.

Recognizing the enormous potential of the gravitational amplification provided by massive clusters, STScI recently dedicated 560 orbits of Director's Time on the Hubble Space Telescope (HST) to extremely deep observations of four carefully selected massive clusters. The images obtained by the Hubble Frontier Fields (HFF) initiative will reach a limiting magnitude of 29 (AB) in each of six passbands covering the entire optical and NIR window. The HFF project represents the largest investment of HST time for deep observations of galaxy clusters in the history of HST. Its main science goal is the discovery of gravitationally lensed background galaxies at z=5-10 for both in-depth studies of bright individual objects and statistical investigations into the properties of galaxies at magnitudes and distances inaccessible to observation without gravitational amplification. As a bonus, the HFF observations will also yield the deepest images of the cores of massive clusters ever collected, thereby facilitating exquisitely detailed characterizations of the cluster lenses and their galaxy content. Two HFF clusters will be observed in each of Cycle 21 and 22; observations will commence in November 2013 and end in June 2015. All data will immediately be available via the HST archive.

We propose a Focus Meeting (FM) on the HFF at the IAU General Assembly in August 2015 to allow observers, theorists, and modelers to present results from the HFF project, discuss new lens modeling techniques, and prepare and evaluate observational strategies to further exploit the HFF with both the James Webb Space Telescope and groundbased 30-m class telescopes.