Active Galactic Nuclei, Supermassive Black Holes, and Galaxy Evolution

My research is focused on Active Galactic Nuclei (AGN) and supermassive blackholes (SMBH). It is currently well accepted that SMBHs resided ubiquitously in the nuclear regions of most massive galaxies and when SMBH are in a phase rapid accretion growth, they are called AGN. It is believed that AGNs may play an important role in moderating star formation in galaxies. Both objects represent an important part of our understanding of the physics of black hole growth and galaxy evolution.

Here I summarize the research I have done.

The Obscured Fraction of Luminous Quasars at Cosmic Noon

Vijarnwannaluk et al. 2022

In this project, we examined the fraction of obscured AGN during the peak era of accretion growth (z~2). There is a trend in which the fraction of obscured AGN increases with redshift but the fraction is not well determined for luminous high redshift AGN. In this project, we used deep and wide X-ray datasets combined with deep optical and infrared datasets to search for the host galaxy of X-ray sources and estimate their redshift.

By using a sample of 306 AGN at z>2, we determined that 76% of luminous high redshift AGN are obscured suggesting that a large fraction of accretion growth occurs under obscuration. We also investigate the spectral energy distribution of unobscured and obscured AGN. We found that both unobscured and obscured AGN show a variety of shapes which may reflect the broad variety of host galaxy properties and physical processes associated with the obscuration

The spectral energy distribution of X-ray obscured and unobscured AGN compared with empirical models.