High Redshift Quasars and
Galaxy Evolution
My research focus is in observational cosmology, more specifically, in high-redshift quasars and active galaxies in general, and in the formation and evolution of galaxies.
With Steidel, I have been also working on studying the impact of quasars on the surrounding IGM. In March and May 2007, using Keck telescope we have made a discovery of huge intergalactic gas “blobs” glowing in Lyman alpha near a luminous quasar at redshift z~2.8. The paper is in the works.
In 2005 and 2006, with S.G Djorgovski, I have conducted a spectroscopic survey to find low-luminosity quasars at redshift z~4.0, from the publicly available NOAO Deep Wide Field survey and Deep Lens Survey. The survey finished with 20 quasars discovered, some of which turned out to be very unique in their spectroscopic characteristics (letter : Discovery of Two Spectroscopically Peculiar, Low-Luminosity Quasars at z~4). The paper describing the whole survey and the observed low-luminosity end of the quasar luminosity function is being finalized.
In previous years I have been searching for highest redshift quasars to study the epoch of reionization (with S.G. Djorgovski, A. Mahabal, Dan Stern and Dave Thompson), using an optical and near infrared survey we did at the Palomar 200” telescope. We have discovered a faint quasar at z=5.7 (Discovery of an Optically Faint Quasar at z = 5.70).
I have also been working for two years on The Palomar-Quest Survey, which is a large area survey conducted with the Palomar 48” telescope, using a wide field-of-view Quest camera (containig no less than 112 CCD chips). One of the notable side projects from the Palomar-Quest survey is the Griffith Observatory Big Picture , which we completed in August 2006.
Most recently, with my thesis advisor Charles Steidel, I am working on detecting and measuring the ammount of escaping Lyman continuum radiation from galaxies at redshifts z~2 to z~3.
The fraction of UV photons which manage to escape from galaxies at high redshift is a key parameter required for our understanding of re-ionization and the physical conditions in the IGM at z>2, but the relationship between this escape fraction and galaxy properties is unknown.
To address this question, we have obtained very deep Keck LRIS-B spectroscopy in the restframe UV for a sample of ~50 galaxies at z~3. This spectroscopic sample in conjunction with optical and near-IR imaging allows us to characterize how properties such as star formation rate, stellar mass and UV morphology of galaxies relate to measurements of flux in the Lyman continuum.
