COSMIC WEB AND STAR FORMATION ACTIVITY IN GALAXIES AT z ∼ 1

We investigate the role of the delineated cosmic web/filaments on star formation activity by exploring a sample of 425 narrow-band selected H alpha emitters, as well as 2846 color-color selected underlying star-forming galaxies for a large-scale structure at z = 0.84 in the COSMOS field from the HiZELS survey. Using the scale-independent Multi-scale Morphology Filter algorithm, we are able to quantitatively describe the density field and disentangle it into its major components: fields, filaments, and clusters. We show that the observed median star formation rate (SFR), stellar mass, specific SFR, the mean SFR-mass relation, and its scatter for both H alpha emitters and underlying star-forming galaxies do not strongly depend on different classes of environment, in agreement with previous studies. However, the fraction of H alpha emitters varies with environment and is enhanced in filamentary structures at z similar to 1. We propose mild galaxy-galaxy interactions as the possible physical agent for the elevation of the fraction of H alpha star-forming galaxies in filaments. Our results show that filaments are the likely physical environments that are often classed as the intermediate densities and that the cosmic web likely plays a major role in galaxy formation and evolution which has so far been poorly investigated.