Title: The activity of galaxies in clusters: decomposing the population of 
massive CLASH galaxy clusters at z~0.45

Abstract:
The massive clusters RXJ1347 and MACS1206, both z∼0.45, have recently been 
observed with 16 filters from UV to NIR (ACS+WFC3) in the central 4.07 
sq.arcmin (~ 3 Mpc regions), as well as several flanking fields in the 
outskirts through the efforts of the multi-cycle HST Treasury program CLASH 
(Cluster Lensing and Supernova survey with Hubble). The wealth of additional 
data available, which includes an extensive spectroscopic follow up, CLASH-VLT, 
and large scale Subaru SuprimeCam observations, enables us to accurately 
determine structural parameters (morphology) and color profiles, while 
combining this with strong- and weak- lensing analyses which provide mass maps 
and reveal substructures of the clusters. In addition, the robust SED fits of 
the galaxies allow derivations of stellar masses, star formation histories, 
dust content and chemical (metallicity) abundances. The quantitative analysis 
of the stellar populations with VIMOS spectra yield stellar ages, metallicities 
and gas abundances, current SF rates and AGN contributions.
The clusters were chosen to study the influence of different environments on 
properties of the galaxy population: RXJ1347 is a highly active massive X-ray 
luminous cluster, where several subgroups fall into the potential of the main 
cluster (observations cover the large-scale cluster structure over 1sq.deg) 
yielding different mixtures of galaxy populations, whereas MACS1206 appears 
relaxed on both optical and x-ray images. 
The intermediate redshifts (z~0.45) of the clusters on the other hand might 
hold clues for the evolution of S0 galaxies: Gas stripping and tidal 
interactions might be an explanation for the transformation of spirals into S0s 
(review in Ziegler (2000)). These processes leave signs, which we can now trace 
and quantify with our data. 
To identify and understand the processes which link galaxy properties to the 
host cluster are the matter of our research: In our studies, we probe a range 
of environments and correlate stellar population parameters, SFRs and AGN 
activity to structural parameters from our morphological analysis. This way, 
processes that influence galaxy properties, and their relative strengths can be 
quantified. Through the efforts of the CLASH and CLASH-VLT surveys, we are able 
to decompose and compare the galaxy populations of an interacting cluster 
(RXJ1347) as well as a relaxed galaxy cluster (MACS1206).