The Universe has proven to be far more intriguing in its composition than we knew it to be. It is a “dark” Universe where 23 percent of its mass-energy density is made up of weakly interacting (and, as yet, undetected) non-baryonic particles (a.k.a. dark matter) and 73 percent is as yet unknown physics (a.k.a. dark energy) that is driving an accelerated expansion. To shed new light on these mysteries, gravitational lensing power of 25 massive galaxy clusters is coupled with HST’s panchromatic imaging capabilities (WFC3 and the restored ACS) to test structure formation models with unprecedented precision.

VLT-CLASH is a spectroscopic follow-up using VLT-VIMOS of a subset of 14 clusters from CLASH. The VLT-VIMOS spectroscopy aims at obtaining redshift measurements for 400-600 cluster members in each cluster field. In particular five emission lines ([OII]3727, Hβ, [OIII]5007, Hα and [NII6584]) are observed for galaxies in three clusters at z~0.45: RXJ1347, MACSJ0329, and MACSJ1206. Our group member Christian Maier is using the five emission line fluxes to get reliable metallicities for cluster members and field galaxies, to study the effect of environment on the mass-metallicity relation of galaxies at z~0.45.

Read more: CLASH