Seminars and Colloquia

Changing Look behaviour in 6dFGS AGNAstrophysics Seminar

by Ms Sruthi Suresh (University of Melbourne)

Asia/Kolkata
Auditorium

Auditorium

Description

Abstract: 

Active galactic nuclei (AGN) are the compact, energetic central regions of galaxies, powered by supermassive black holes that accrete surrounding gas and dust. Understanding AGN is essential to uncover how black holes co-evolve with their host galaxies. While northern surveys such as SDSS have mapped AGN extensively, the Southern Sky remains comparatively underexplored. To bridge this gap, we present Type 1 and Type 2 AGN catalogues from the Six-degree Field Galaxy Survey (6dFGS), which contains over 136,000 spectra covering ~17,000 deg2 of the southern sky. We identify emission-line galaxies using a statistical cut and fit their spectra with the Python-based fitting tool PyQSOFit. 2,515 Type 1 and around 5,000 Type 2 AGN are classified using the optical flux ratios. Multi-wavelength analysis of this southern AGN sample reveals a subset of sources showing signs of Changing-Look (CL) behaviour, dramatic transitions in their spectral type that may reflect rapid changes in accretion states. These systems provide valuable insight into the dynamic nature of black hole growth. With the start of the Legacy Survey of Space and Time (LSST), this catalogue establishes a critical foundation for alert-driven AGN monitoring in the Southern Hemisphere, enabling rapid identification and follow-up of CLAGN.