Main sequence of star formation and colour bimodality considering galaxy environment

TL;DR

This study investigates how galaxy environment affects the main sequence of star formation and colour bimodality using SDSS DR12 data, revealing significant environmental influences on galaxy properties and distributions.

Contribution

It introduces a method to classify galaxies by environment and demonstrates the impact of environment on star formation and colour distribution, with detailed quantitative analysis.

Findings

Decreased slope and intercept of the main sequence in different environments.

Significant differences in galaxy counts across star formation and colour categories.

Environmental influence on galaxy evolution and distribution patterns.

Abstract

This study involves the use of friend-of-friend method on the volume limited samples constructed from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12) to classify the galaxies into isolated and non-isolated environments hence to investigate the influence of the galaxy environment on the main sequence of star formation, and colour bimodality. We classified the galaxies into the luminous volume-limited sample with $ -22.5\leq M_r \leq -20.5$ (mag), and the faint volume-limited sample with $-20.5 \leq M_r \leq -18.5$ (mag). Using the WHAN diagnostic diagram we assignedthe samples into star-forming, strong AGN, weak AGN, and retired galaxies based on their environment (isolated and non-isolated). The friend-of-friend method was successful in producing consistent results regarding the stellar mass-SFR and stellar mass-colour known relations. Apart from that the decrease in the slope of the main sequence for star-forming galaxies by $0.04$ dex and intercept by $0.39$ dex for the luminous sample was observed while the faint sample a decrease of $0.08$ dex in slope and $0.74$ dex in intercept was observed between isolated and non-isolated galaxies. A significant difference on the number of galaxies between isolated and non-isolated galaxies within, above and below the main sequence by $7.47\%$, $28.51\%$, $14.59\%$ for the luminous sample while for the faint sample by $16.15\%$, $32.60\%$, $35.23\%$ on average, respectively are observed. A significant difference in the number of galaxies in the blue cloud, green valley, and red sequence by $10.30\%$, $20.61\%$, $5.74\%$ for luminous sample while for faint sample by $28.46\%$, $41.36\%$, $8.95\%$ on average, respectively was observed. The study concludes that the galaxy environment influences the shaping and positioning of galaxies along the star formation main sequence and colour bimodality.