NOAO >   Observing Info >   Approved Programs >   2003A-0419

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Proposal Information for 2003A-0419


PI: Ana Matkovic, University of Florida, matkovic@astro.ufl.edu
Address: Department of Astronomy, 211 Bryant Space Sciences Center BOX 112055, Gainesville, FL 32611, USA

CoI: Rafael Guzman, University of Florida

Title: Testing The Galaxy Harassment Scenario for The Formation of Cluster Dwarf Ellipticals

Abstract: One of the main unanswered questions in modern cosmology is the nature of the Butcher-Oemler effect: the observation of numerous star- forming, low-mass, 'blue disk' galaxies in clusters at z ~ 0.4 that are absent in today's clusters. A promising new theoretical model shows that gravitational interactions with massive cluster galaxies may transform these blue disks into today's population of cluster dwarf ellipticals (dEs). The so-called 'galaxy harassment' scenario predicts that, on average, dEs located in the inner, high-density cluster regions should be more metallic and have larger velocity dispersions than those in the outer regions. However, no such differences have yet been observed due to a lack of a statistically representative sample of dEs including velocity dispersions and metallicities. We propose to test this model by comparing the metallicity and kinematics of dEs located in the inner and outer regions of the Coma cluster. We have already obtained WIYN/HYDRA spectra of ~50 dEs in the inner 1^\circ region of Coma to measure their velocity dispersions and line strength indices. Here we propose to obtain spectra of ~50 dEs in the outer regions using WIYN/HYDRA. The measurements of the same properties in the outer parts of the cluster are crucial in our effort to determine the validity of the 'galaxy harassment' model.


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