Large Hα surveys of field, filaments and (proto-)clusters at z∼0.2−2.2: does the environment matter?

I will present results from the largest narrow-band surveys for Hα emitters in and around the richest clusters at z ∼ 0.2 − 0.4 and over the general large scale structure, including proto-clusters, up to z ∼ 2.2. Our follow-up spectroscopy allows us to further investigate the nature and physical properties of star-forming galaxies and AGN within some of the most massive relaxed and merging clusters, and to directly contrast them to equally selected galaxies in the field and in filaments and to clusters and proto-clusters at higher redshift. We find interesting similarities between filament and merging cluster galaxies, but also point out how some Hα over-densities at higher redshift are likely group/filament structures instead of proto-clusters. I will finish by exploring the nature of a unique proto-cluster (9σ overdensity) surrounded be a potential filamentary structure in the COSMOS field, revealed by our very wide field Hα survey.