Galaxy Interaction in Overdense Environments
Abstract
Examining protoclusters is an important method for developing our understanding of the formation and evolution of large galaxy clusters found in the local universe. Many of the z≈2-3 protoclusters contain overdensities of dusty star-forming galaxies (DSFG) which have stellar formation rates greater than 100 Msun/year. Due to the short depletion time (≈100Myr) of molecular gas in the DSFGs contained in these protoclusters, the assembly of protoclusters is believed to be a rapid and occasional process. One possible mechanism for this rapid assembly is an enhanced frequency of interaction between galaxies. We analyzed one of these protoclusters at z= 2.1 to determine if the frequency of mergers is affected by the overdense environment. Previous works have shown that galaxies may interact more frequently in overdense environments but do not provide adequate significance to confirm this connection. Using the COSMOS2015 catalog, galaxies in the protocluster are evaluated with the following criteria for merger candidates: existence of neighboring galaxies in a 10-30 kpc radius, agreement of photometric redshift with neighbor(s) within 1σ, and stellar mass ratio calculation for merger candidates in terms of minor mergers (>4:1) and major mergers (1:1 - 4:1). Our analysis confirms that interacting galaxies are found more frequently in overdense environments (δ > 0.5). Based on further analysis using spectroscopic redshifts from the ZFIRE Survey to evaluate the uncertainty present by using the photometric redshifts, we find that σΔ/(1+z_s) = 0.05 for the photometric redshifts from z= 1.50 to z= 2.50. In the future it will be helpful to analyze mergers in other stages of interaction to see if the enhanced merger frequency is still evident.
- Publication:
-
American Astronomical Society Meeting Abstracts #229
- Pub Date:
- January 2017
- Bibcode:
- 2017AAS...22924605H