Goals of the CLASH Program

By observing 25 massive galaxy clusters with HST's panchromatic imaging capabilities, CLASH accomplished its four primary science goals:

  • Map 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 measure the role of dark energy over time and look for any evolutionary effects in the supernovae themselves;
  • Detect and characterize distant galaxies at z > 7 (when the Universe was younger than 800 million years old);
  • Study the internal structure and evolution of the galaxies in and behind these clusters.

  • The CLASH program was awarded a total of 525 orbits of time on HST to conduct its observations. The observations of these 25 clusters were scheduled and performed over a 2.7 year period (Nov 2010 - July 2013). The images of the clusters were acquired using Hubble's Advanced Camera for Surveys (ACS) and both the UVIS and IR channels of the Wide-Field Camera 3 (WFC3). CLASH was a multi-cycle Treasury program and, as such, all its HST data were immediately released for public access via the MAST archive.

      Science Highlights from CLASH

    The people behind CLASH

    The CLASH team consisted of over 55 astronomers from 10 different countries and located at over 25 institutions. Find out more about the researchers that conceived, planned, and created the CLASH program and its scientific data.

    Other Resources & Related Projects

    CLASH was a multi-wavelength, multi-observatory project. Here we list some of the other resources, such as our ground-based VLT spectroscopic survey, that helped enable the full range of CLASH science. We also provide links to programs that were inspired by CLASH to further study the universe as seen through nature's largest gravitational lenses.

    • CLASH-VLT Program

      A panoramic spectroscopic survey with VIMOS on the European Southern Observatory's VLT was conducted to provide essential redshift and astrophysical information on the galaxies in the CLASH fields. This VLT large project targeted 12 of the CLASH clusters, with redshifts between z = 0.2-0.6, that are visible from the southern hemisphere. The program acquired over 31,000 galaxy spectra. The redshift catalogs are being made available via MAST.

    • Hubble Frontier Fields

      Inspired, in part, by the success of CLASH, the Space Telescope Science Institute initiated a community-led program to observe 6 massive galaxy clusters (4 of which were part of the CLASH program) to flux limits 10x fainter than those achieved in CLASH. The program was dubbed the Hubble Frontier Fields and provides a first look at the galaxy populations in the early universe that will be explored in great detail with the James Webb Space Telescope.

    • HFF Lens Models

      The public Frontier Fields lens models include maps of mass (kappa) and shear (gamma) from which magnifications can be derived at any redshift using the script provided. Magnification maps pre-computed at z = {1,2,4,9} are also available for download at this site. Four of the six models are for clusters in the CLASH sample.

    • RELICS Program

      Building on the successes of CLASH and the Frontier Fields, and optimizing our survey for high-redshift discovery, the Reionization Lensing Cluster Survey (RELICS) has delivered candidates for the brightest galaxies known in the first billion years at z ~ 6 (Salmon et al. 2017) and the most distant galaxy lensed to form an arc at z ~ 10, observed 500 million years after the Big Bang (Salmon et al. 2018). Learn more about the RELICS program and access its data.

    • Grism Lens-Amplified Survey from Space

      The GLASS project was a slitless (grism) spectroscopic survey, performed with the Hubble Space Telescope, of 10 massive clusters, including 8 CLASH clusters. The survey observed these 10 clusters using the G102 and G141 grisms and observed parallel fields adjacent to the clusters with the G800L grism. Using the clusters as cosmic telescopes, GLASS acquired spectra of faint background galaxies with unprecedented sensitivity and angular resolution.

    • Archive of Chandra Cluster Entropy Profile Tables

      ACCEPT is a research tool for astrophysicists interested in the high-energy (X-ray) properties of galaxy clusters. ACCEPT is a large, uniformly analyzed database of many cluster properties, including the X-ray surface brightness profiles, ICM temperature profiles, and entropy profiles. Many of the CLASH clusters are included in the ACCEPT database.