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Session 48 - Spiral & Field Galaxies.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center
In the three decades since Lin and Shu (1964, ApJ, 140, 646) introduced the spiral density wave theory a persistent question remains. How efficient are spiral galaxies in accumulating mass in their arms? Rix and Rieke (1993, ApJ, 418, 123) in an extensive study of M51 found that the luminous mass density is accurately traced by K band photometric measurements. Rix and Zaritsky (1995, ApJ, 447, 82), in a study of face-on spiral galaxies, find further evidence that K band intensity variations trace the mass distribution in a galaxy with an error of less than 20report that nearly half of their galaxies exhibit spiral arm intensities which are twice that of the interarm regions.
Photometric images of a random sample of nearby spiral galaxies obtained at J and K have been analyzed to produce spiral arm amplitudes. Preliminary results indicate that there is on the order of twice as much luminous mass in a spiral arm as there is in the adjacent interarm region. The effect seems to be larger at K than at J. These amplitudes provide a serious constraint on theoretical models which predict disk temperature and density fluctuations.
