About Our Survey

Scientific Objectives of CLASH:

By observing 25 massive galaxy clusters with HST’s panchromatic imaging capabilities (Wide-field Camera 3, WFC3, and the Advanced Camera for Surveys, ACS), CLASH accomplishes its four primary science goals:

Map, with unprecedented accuracy, the distribution of dark matter in galaxy clusters using strong and weak gravitational lensing;


Detect Type Ia supernovae out to redshift z ~ 2, allowing us to test the constancy of dark energy's repulsive force over time and look for any evolutionary effects in the supernovae themselves;


Detect and characterize some of the most distant galaxies yet discovered at z > 7 (when the Universe was younger than 800 million years old - or less than 6% of its current age);


Study the internal structure and evolution of the galaxies in and behind these clusters.

The CLASH program has observed these 25 clusters over a 2.7 year period (Nov 2010 - July 2013). The program was awarded a total of 524 orbits of time on HST to conduct this program. CLASH is a multi-cycle Treasury program and, as such, all its HST data are immediately released for public access via the MAST archive.


The CLASH program observed the clusters with the Advanced Camera for Surveys (ACS) and both the UVIS and IR channels of the Wide-Field Camera 3 (WFC3). Detailed descriptions of ACS and WFC3 are available on-line (click the links).

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