Thursday

One of the key results in the field of galaxy clusters show that there is a close link between the galaxy density and their morphology in the local Universe (see e.g. Dressler et al. 1980). At higher redshifts this picture is unclear as evolved clusters are rarer and the imprint on morphology is less pronounced. With a wealth of imaging data from publicly available surveys and dedicated VIMOS observations of a highly clustered region in the COSMOS field (Darvish et al. 2014) we investigate the links between galaxy morphology, star-formation activity (traced by [OII] and Hd in the VIMOS spectra), and environment at z~1.
We find that there is a break on the average galaxy size, with high density regions having smaller galaxies when compared to the filaments and field regions. We also see signatures for profile changes with density, by observing higher Sérsic indexes (indicative of more elliptical-like galaxies) in the higher density regions. Our results show that there is already some morphological differentiation through local density taking place when the Universe had roughly half of its current age.