Environmental Dependence of Barred and Unbarred Narrow-Line Seyfert 1 Galaxies

Project Description

Narrow-line Seyfert 1 (NLS1) galaxies are a distinct class of active galactic nuclei (AGNs) characterized by relatively low black hole masses and high Eddington ratios. These properties suggest that NLS1s are experiencing rapid black hole growth and may represent an early stage of AGN evolution. Understanding how AGN activity is triggered in NLS1 galaxies is therefore crucial for revealing the physical mechanisms governing black hole growth and galaxy evolution. Recent studies indicate that NLS1 galaxies exhibit diverse host-galaxy properties. While some NLS1s reside in galaxies with prominent stellar bars, suggesting AGN fueling driven by internal secular processes, others lack such structures. This raises an important open question: if unbarred NLS1 galaxies are not fueled by internal bar-driven mechanisms, what alternative processes trigger their AGN activity? This summer research project explores the role of galaxy environment and interactions as potential external triggers of AGN activity in unbarred NLS1 galaxies, using large-scale survey data and statistical analysis.

Topic A: Do unbarred NLS1s preferentially reside in denser environments?

In this project, the student will investigate whether unbarred NLS1 galaxies preferentially reside in denser environments compared to barred NLS1s. Using an existing, well-defined sample of NLS1 galaxies, the student will quantify local galaxy environments through statistical measures such as nearby galaxy number density and nearest-neighbor distances derived from optical survey catalogs.

Topic B: Are unbarred NLS1s more likely to be associated with recent or ongoing galaxy interactions?

This project focuses on identifying signatures of recent or ongoing galaxy interactions associated with unbarred NLS1 galaxies. The student will examine the frequency of close galaxy companions around unbarred NLS1s and compare it to that of barred NLS1s. By analyzing projected galaxy pairs and relative velocities, the project aims to assess whether unbarred NLS1s are more strongly linked to interaction-driven AGN triggering.