Richard Green

Tucson Nighttime Scientific Staff


Areas of Interest

Active Galactic Nuclei, Quasar Absorption Line Systems, Galaxy Nuclear Dynamics

Recent Research Results

Near-UV echelle data from the 4-meter have been acquired for studying metal-line and Lyman alpha absorption systems observed in lines of sight to distant quasars. Recent analysis of spectra of the quasars MC3 1331+170 and B2 1225+317 by York, Green and their collaborators shows that the pattern of abundances of the chemical elements can be used to model the star formation history of the absorbers. Some differences are seen when compared to the fossil record of abundances in the oldest stars in the Galaxy. Osmer, Hall, Liu and Green are pursuing a multi-color survey of about a square degree of sky at high galactic latitudes, that is complete to near 23rd magnitude in V. Recent papers address the evolution of the quasar and Seyfert galaxy luminosity functions. The low surface density of high-redshift objects confirms earlier work that there was a "quasar epoch" around z=2 prior to which the density of observable objects was significantly lower. In addition, Liu's thesis supervised by Green will address the frequency of star formation episodes through the incidence of E+A galaxies and the evolution of star-formation rate in galaxies, based on a color-selected sample from the same imaging database. Green's participation in the Hubble Space Telescope Medium Deep Survey Key Project has led to papers by thesis student V. Sarajedini and team collaborators on the incidence of stellar nuclei in faint field galaxies. The goal is to define the evolution of the faint end of the Seyfert nucleus luminosity function.

Future Research Plans

During the next Agreement period, Green will concentrate on research related to two NASA orbital instruments, for which he has served for more than ten years on the instrument definition teams. The first program is based on data from STIS, the Space Telescope Imaging Spectrograph, currently scheduled for deployment in February, 1997. Green leads the GTO team's internal key project on galaxy nuclear dynamics. The goal will be to analyze spectra with high spatial resolution to determine the demographics of Black Holes in the nuclei of ellipticals and other non-active galaxies. The next program is that of FUSE, the Far Ultraviolet Spectroscopic Explorer satellite. The team's goal is to measure the primordial deuterium to hydrogen ratio as a diagnostic of physical conditions in the nucleosynthesis phase of the Hot Big Bang. Since deuterium is easily destroyed in stellar fusion reactions, we must extrapolate the D/H ratio as a function of metallicity of absorbing gas, which reflects the degree of modification of primordial abundances by stellar processing.

Service

Responsibilities as Deputy Director:


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Posted: 06Dec1996