Metal enhancement of the protocluster galaxies at z=2.2

[Speaker 1]
Rhythm Shimakawa M2, SOKENDAI, Mitaka(supervisor : Kodama Tadayuki)
Metal enhancement of the protocluster galaxies at z=2.2
Protoclusters are the ideal laboratories to study how the strong environmental dependence in galaxy properties seen today was initially set up. We conducted a near-infrared spectroscopy of star-forming galaxies (H-alpha emitters) associated with two protoclusters at z=2.2&2.5 with MOIRCS/Subaru.
Shimakawa et al. (2014) have confirmed that the two protoclusters are the right ancestors of today’s largest clusters like ‘Coma’, and now we are studying the physical characteristics of the memberships in the respective protoclusters.
This talk focuses on one of our recent results regarding the environmental dependence of mass-metallicity relation seen in the protocluster, PKS1138-262 at z=2.2. The mass-metallicity relation provides crucial insights into star formation history, gaseous inflows and outflows.
As a result, we find a clear excess of the gaseous metallicities of the protocluster galaxies at the stellar mass of < 1E11 Msun. We suggest that it can be explained by the 'downsizing effect' or 'gas recycling' in the protocluster region.