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The Subaru Seminar is usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you are interested in giving a seminar, please contact Subaru seminar organizers (Tadayuki Kodama, Kumiko S. Usuda, Naoyuki Tamura, Tomonori Usuda) by email : (please change"_at" to @).

June 22, Tuesday, at 11:00 am

" Compact Star Clusters in M31 Disk "

Keiichi Kodaira

(JSPS Bonn Office)

During the verification period of Sprime-Cam we obtained high-resolution images of the southwest part of the M31 disk (500 squarearcminutes). Using these images, a full-field search for compact non-stellar objects with apparent size less than 3arcsec (corresponding to about 10pc) was carried out, to identify about 300 candidates for compact star clusters. They looked similar to globular star clusters but some with little irregularities, and included many blue objects of B-V<0.5. After closer inspections we selected 238 highly probable candidates for compact star clusters (V<20.5mag) and performed an accurate surface-photometric study. The calibrated UBVRI data were applied to derive cluster parameters related to structure, age, mass, metallicity, and interstellar extinction. The outcome of this study indicates that there are abundant star clusters, which have the intermediate properties between the open clusters and the globular clusters well known in our Galaxy, bridging between the two populations. Their spatial distribution on the M31 disk shows loose connection to 24micron warm cloud structures. Whether this new population of clusters identified in M31 disk does also exist or not in our Galaxy disk, is still an open question. These clusters might be powerful tool to elucidate the evolution history of galaxy disks.

Seminars are also held at JAC, CFHT, and IfA.

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