NOAO >   Observing Info >   Approved Programs >   2007A-0276

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Proposal Information for 2007A-0276


PI: David Andersen, NRC Herzberg Institute of Astrophysics, david.andersen@nrc-cnrc.gc.ca
Address: 5071 W. Saanich Rd, Victoria, BC V9E 2E7, Canada

CoI: Carl Jakob Walcher, LAM, Marseilles
CoI: Hans-Walter Rix, MPIA, Heidelberg
CoI: Luis Ho, Observatories of the Carnegie Institution

Title: Do Bulge-less Galaxies have a Center?

Abstract: The nuclear regions of galaxy bulges are closely related to the evolution of their surrounding hot stellar systems. It is not clear if the centers of very late type (i.e. bulge-less) galaxies are as well- defined and decisive for their host galaxies evolution. Studying the centers may provide clues as to why this special group of galaxies never built up dynamically hot component in the first place. Most very late type, bulge-less spirals, however, do appear to host stellar nuclei: central, massive, multi-age, compact star clusters of ~10^6M_\odot. Apparently these galaxies also have centers with special physical properties, as is the case in early type galaxies. Perhaps more surprisingly, 25% of these bulge-less galaxies do not contain nuclear clusters (NCs). Little is known about why the nucleation process appears to be triggered in most galaxies, but not in others. Therefore, we propose to observe the galaxy kinematics of 16 late-type galaxies both with and without NCs using the IFU DensePak on WIYN. If the velocity fields of galaxies with NCs are ordered and have clear kinematic centers coincident with the NCs while the velocity fields of galaxies without NCs are more asymmetric, we will infer that NCs are indeed special and that the gravitational potential of galaxies with and without NCs are fundamentally different. Alternatively, if there are no discernible differences in the velocity fields and NCs are not always found to be coincident with the kinematic center, then we will conclude that NCs are formed through a stochastic process.


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