Astronomy Tea Talk

The environment is known to influence galaxy formation and evolution
through studies of the relationship between galaxy overdensity and
galactic properties at lower redshifts. At higher redshifts, however,
it is less certain whether the environment plays an equally important
role in galaxy evolution. The methodology to define the large-scale
galaxy environment is one of the challenges of such studies. At z = 2,
galaxy distributions and the Lyα forest tomography are now considered
as observational probes for the large-scale structure. This talk will
present spatial correlation of those two independent observational
probes for the large-scale structure and discuss their use as a probe.
In addition, I will also talk about the results of the environmental
effect of galaxy evolution at z = 2 in the COSMOS field. The unique
aspect of this second topic is evaluating the large-scale environment
by looking at the dark matter density itself, rather than galaxy
overdensity, based on the former part of this talk. Utilizing the
matter density maps, we examined the dependence of the star formation
activities and galaxy types (mergers, submillimeter galaxies, active
galactic nuclei, and quiescent galaxies) on the local matter density,
cosmic web structures, and stellar mass. I will present those results
and a scenario for galaxy formation and evolution indicated from them.
I will also discuss our new approach with matter density for studying
environmental effects at higher redshifts.