Research Interests

My primary research interest is the study of active galactic nuclei (AGNs) at moderate to high redshifts through their morphological characteristics, spectroscopic signatures and variable nature.

My thesis research (completed at the University of Arizona in August of 1997) consisted of a search of active nuclei in Hubble Space Telescope images based on their morphology. An AGN will manifest itself as an unresolved nucleus in the center of a galaxy. This figure shows several galaxy images from the Medium Deep Survey which reveal central unresolved nuclei comprising as little as 3% of the total galaxy light. Notice that the majority of galaxies hosting these nuclei appear spiral in nature.

AGNs are also identified based on their spectroscopic characteristics. The DEEP project at the University of California, Santa Cruz, has been obtaining spectra of several hundred galaxies with the Keck Telescope on Mauna Kea, Hawaii. Here is an example of one of these spectra which clearly indicates the presence of an active galactic nucleus by the broad Magnesium II emission line at 2799 angstroms (at a redshift of z=1.22). By searching for broad emission lines and narrow emission lines having specific intensity ratios, we are investigating the number density of AGN at z ~ 1.

AGN can also be detected through their variable nature. Observations of the Hubble Deep Field (shown left) taken originally in 1994 and repeated in 1996 reveal 8 galaxies with varying nuclei (Sarajedini et al. 2000). These are likely to be Seyfert-like galaxies. They have a mean redshift of z~0.8 and a variety of morphologies. A third epoch of HDF imaging has recently been obtained and will be used to confirm these results. I will be conducting a similar variability survey to look for AGN in the Groth Survey Strip. Stay tuned for the results of this study which should yield a much larger sample of active galaxies at z>0.5.