LOCAL ENVIRONMENTAL EFFECTS ON AGN ACTIVITIES

Abstract

< 19) sampleof galaxies via visual inspection and the de nition of galaxy pair systems based on the Sloan Digital SkySurvey Data Release 7 in order to con rm the e ects of galaxy interaction on AGN activities. We foundthat local environmental e ects such as galaxy interaction have an inuence on the enhancement of thefrequency and the strength of the AGN activity. This article is the summary of the paper which will besubmitted soon.Key words: galaxies: active - galaxies: interactions1. INTRODUCTIONActive Galactic Nucleus (AGN) are one of the most pow-erful objects in the universe. These days, it is gener-ally accepted that AGNs are powered by the accretionof materials onto a supermassive black hole (SMBH;Lynden-Bell et al., 1969), which is located in the centerof the galaxy. Over the last few decades, there have beenmany studies of the physical mechanisms powering theAGN. Several mechanisms, including stellar winds, diskinstabilities and galaxy-galaxy interactions, have beenproposed to explain this phenomenon, but the primarymechanism that turns a quiescent SMBH into an AGNis still unclear.Of these mechanisms, galaxy mergers provide an ap-pealing mechanism for triggering galactic nuclear ac-tivities, as modern cosmology predicts that there arefrequent interactions between a galaxy and its environ-ment during its evolution. Many statistical studies havebeen undertaken with large samples, to investigate thelink between AGN host galaxies and their environments.Some found some hints for the positive e ects of envi-ronments on AGN activity (Miller et al., 2003; Kau -mann et al., 2004; Serber et al., 2006; Alonso et al.,2007; Koss et al., 2010; Schawinski et al., 2010; Ellisonet al., 2011; Silverman et al., 2011; Liu et al., 2012),but others found no signi cant evidence (Schmitt, 2001;Grogin et al., 2005; Coldwell & Lambas, 2006; Gabor etal., 2009; Sabater et al., 2012). Several factors includingAGN diagnostics, data sets, and particularly the de ni-tion of the merger criteria, may contribute to these con-troversial results. In this study, we tried to statistically nd the link between the local environment surroundinggalaxies and galactic activity, using homogeneous sam-http://pkas.kas.orgples.2. DATA & METHODOLGYUsing the nearby(0.01< z <0.05) volume-limited(M