Contributed Talk - Splinter SMBHs

Wednesday, 23 September 2020, 12:10   (virtual room K)

Environmental Effects on AGN Activities via Extinction-free Mid-Infrared Census

Daryl Joe D. Santos, Tomotsugu Goto, Seong Jin Kim, Ting-Wen Wang, Simon C.-C. Ho, et al.
Institute of Astronomy, National Tsing Hua University

This study focused on unveiling the relationship between star formation/active galactic nucleus (SF/AGN) activity and environment of galaxies with mid-infrared (MIR) and far-infrared (FIR) detections in the AKARI North Ecliptic Pole Wide (NEPW) field in the redshift range 0 < z < 1.5. The AKARI satellite, compared to other infrared (IR) telescopes (e.g., WISE and Spitzer), has the unique continuous 9-band filter coverage that provides more detailed photometry, thus allowing us to better characterize features that appear in the MIR. We constrained the properties of the selected galaxies using CIGALE, a spectral energy distribution (SED) fitting code. We also defined several parameters to describe the galactic environments of our sample: local galaxy density, clustercentric distance, and cluster-field galaxy classification. The AGN contribution fraction (ratio between the AGN luminosity and total IR luminosity) and the AGN number fraction (ratio of the number of AGNs over the total number of galaxies) were used as probes of AGN activity in this study. The specific star formation rates of the sample galaxies were also investigated. Both definitions of AGN activity showed consistent trends: AGN and star-formation activities decrease with denser environments only for ultra-luminous infrared galaxies (ULIRGs). This suggests that the environmental effect on quenching galactic activities is more effective in ULIRGs than less luminous galaxies. We present our current progress and possible physical explanations for our results.