Statistical Analysis of AGN Fraction as a Function of Projected Separation in SDSS Galaxy Pairs

Abstract

Galaxy mergers and gravitational interactions are considered critical mechanisms for driving galactic gas reservoirs into nuclear scales, thereby triggering active galactic nuclei (AGN). In this study, we present a systematic statistical framework to investigate the AGN fraction as a function of projected physical separation (r_p) using an interacting galaxy pair sample selected from the Sloan Digital Sky Survey (SDSS). We construct an automated data analysis pipeline in Python to extract emission-line fluxes and classify the primary ionization sources utilizing the BPT diagnostic diagram with the theoretical boundary defined by Kewley et al. (2001). Our statistical analysis demonstrates a significant, monotonic increase in the AGN fraction at tight separations (r_p < 25 kpc), peaking at approximately 14.80%, which represents a threefold enhancement compared to isolated control environments. This small-scale environmental dependency indicates a distinct physical time-lag between large-scale tidal starbursts and the subsequent activation of supermassive black holes (SMBHs).