Description |
For deep imaging longward of 100 um, confusion noise sets the fundamental sensitivity limits achievable with Herschel, and these limits cannot be improved by integrating longer. To penetrate through this confusion limit and detect faint high-redshift galaxies, gravitational lensing by massive galaxy clusters offers a very powerful and yet cheap solution. For this reason, our team has been conducting a PACS/SPIRE imaging survey of 44 massive lensing clusters as one of the Herschel Key Programs, The Herschel Lensing Survey (PI: Egami, 292.3 hrs). Deep PACS/SPIRE imaging data of massive clusters are quite rich with a variety of information, which allows us to study not only the properties of gravitationally lensed high-redshift galaxies but also those of cluster member galaxies and the intracluster medium through the analysis of the Sunyaev-Zeldovich effect.
In January 2010, a massive HST program targeting powerful lensing clusters was accepted as one of the three multi-cycle treasury (MCT) programs. This program, ``the Cluster Lensing And Supernova survey with Hubble (CLASH), has an allocation of 524 orbits, and will obtain deep ACS and WFC3 images of 25 massive galaxy clusters using 16 broad-band filters from near-UV (2250 A) to near-IR (1.6 um). These extensive multi-filter imaging observations will produce high-precision photometric redshifts (sigma/(1+z)<0.02). On average, the program spends 20 orbits per cluster. Considering this enormous investment of HST time, the CLASH program will define the ultimate sample of massive galaxy clusters on which future studies will focus.
Here, we propose to obtain deep PACS and SPIRE images for 10 CLASH clusters that still lack such data (the other 15 clusters already have a good Herschel coverage). To fully exploit the combination of the Herschel and HST data, the HLS and CLASH teams are submitting this proposal jointly with the participation of key scientists from both teams. |