NOAO >   Observing Info >   Approved Programs >   2008B-0419

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Proposal Information for 2008B-0419


PI: Christopher J. Conselice, University of Nottingham, conselice@gmail.com
Address: Physics Department, University Park, Nottingham, Nottingham NG7 2RD, UK

CoI: Greg Bothun, University of Oregon

Title: Spectroscopy of Galaxy Aggregates in Nearby Galaxy Clusters

Abstract: We propose to obtain spectroscopy for three unique galaxy `aggregates' found in nearby clusters at z < 0.03 whose structure/morphology and integrated properties strongly suggest they are in a very rapid stage of galaxy assembly. These aggregates are potentially sub-units, gravitationally bound to one another, which are coming together for the first time to form a larger unit. Ground based imaging of these systems reveals a remarkable ensemble of approximately a dozen extremely blue (V-I=0+/-0.1) "knots" of size 2-5 kpc and absolute V magnitudes of -15 to -17 distributed over a total linear extent of ~ 45 kpc. Aggregate starlight is equivalent in luminosity to M33 and observed integrated H I masses are approximately 5 \times 10^9 solar masses. In all respects galaxy aggregates bear the signature of galactic sub-units merging for the very first time into a large body, potentially induced by the cluster potential. Given their low redshifts, we have the extraordinary opportunity to study in detail this assembly process in action. We therefore request two nights of 2.1 meter time to acquire low-resolution spectroscopy that will allow for a better characterization of the star formation, rotation, and stellar populations of these multiple bright knots in these very unusual and enigmatic galaxies.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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