AAS 207th Meeting, 8-12 January 2006
Session 64 ISM outside the Milky Way
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[64.14] An HST Archival Survey of Spiral Arm Substructure

M. La Vigne, S. Vogel, E. Ostriker (University of Maryland)

We present a survey of spiral arm substructure using HST WFPC2 images, along with BIMA SONG CO 1-0 data where available. The sample includes all 235 galaxies in the RC3 catalog with Vsys \(<\) 5000 km s\(-1\), B\(T\)-magnitude \(<\) 15, inclination \(<\) 60\degr\, and types Sa--Sd which have well-exposed broadband WFPC2 images. Well-defined spiral arms appear in exposures available for 68 galaxies. Of these, 21 have regular substructure commonly referred to as spurs or feathers, and another 21 have possible substructure. The probability of finding substructure increases with spiral arm and main dust lane definition. For those galaxies with BIMA SONG CO 1-0 maps, we find that substructure tends to be associated with high gas column density regions, and that the spacing is inversely related to gas surface density. The substructure has properties such as shape, size, spacing, and galaxy location consistent with predictions of both the Balbus (1988) and Kim & Ostriker (2002) models. Partial support for this work was provided by NSF award AST-0228974.

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