The theme of my research is the history of galaxy formation and evolution, which I explore by charting the development and production of metals in the universe. My research program has both theoretical components (numerical components, photoionising models) and observational components (ground-based and HST imaging, low and high resolution spectroscopy). It includes studies of objects at high redshift as well as some in the nearby universe at present.

My primary efforts fall into three categories.

           Galaxy Evolution through Quasar Absorption Lines

           Central Engines of Quasars - Intrinsic Absorption Systems

           Formation of Dwarf galaxies and star clusters in tidal interactions

       Visit the Quasar Absorption Line Research Group Page

  GALAXY EVOLUTION THROUGH QUASAR ABSORPTION LINE

Quasar Absorption Lines (QAL) have provided a unique view of the evolution of the gaseous content of the universe, unbiased by whether the gas produces light. Using this tool, we can study forming galaxies, dwarf galaxies, and the intergalactic environment, as well as the interstellar medium and halos of giant galaxies. Distant quasars serve as flashlights whose light is observed by various chemical elements in intervening galaxies. The spectra of quasars provide a sensitive probe of the internal workings of galaxies. The challenge remains to decode the spectra in order to identify the signatures of galaxies disks, halo high velocity clouds, satellite galaxies, superbubbles, galaxy pairs and groups etc. Once the code is broken the story of galaxy formation and evolution will unfold before us.

CENTRAL ENGINES OF QUASARS

In perhaps 30% of quasars, narrow absorption lines (NALs) are produced by material along the quasar line of sight that is part of the environment of the quasar central engine. Other quasars exhibit broad absorption lines (BALs). This material can allow us to diagnose the physical conditions in the vicinity of the quasar, and therefore to begin to understand its fueling and energy production mechanisms. This research effort was serendipitously "triggered" by former Penn State graduate student Rajib Ganguly, who subsequently completed a thesis on this topic. It is a joint effort now with Ganguly (now at University of Wyoming) and Mike Eracleous at Penn State.

GALACTIC TRAIN WRECKS

The origin of dwarf galaxies of various types is another part of the puzzle of structure formation. Compact groups of galaxies provide a laboratory for studying mergers and interactions which are important for determining galaxy morphology, and which may have been much more common in the distant past. In collaboration with Sally Hunsberger (Penn State Ph. D, 1998) and Sarah Gallagher (Penn State Ph. D, 2002), Penn State post-doc Chris Palma and other colleagues, I have been surveying the dwarf galaxy population in the Hickson compact groups, and studying their properties. We are working on collecting more data to help us understand the mechanism of formation of tidal and intragroup star clusters.

Watch STScI outreach movie on interacting galaxies of the Stephan's Quintet.

PEOPLE

Collaborators

       Mike Eracleous    Associate Professor     Pennsylvania State University

       Chris Churchill     Assistant Professor     New Mexico State University

       Chris Palma         Lecturer                       Pennsylvania State University

       Rajib Ganguly      Post Doc                       Univeristy of Wyoming

Post Docs

      Toru Misawa


Students

       Theres Jones               Brian Lacki                    Ryan Lynch               Andrew Mshar

       Nikola Milutinovic        Anand Narayanan          Jian Wu