Title:　Gaseous Substructures of Spiral Arms in Disk Galaxies   　　  

    Speaker: Woong-Tae Kim (Seoul National University) 　　  

    Time: Thursday, 3:00pm, May 15th
    
     　　
    

　　Location: Lecture Hall, 3rd floor 　　  

　　Spiral arms are abound with secondary structures such as young stellar complexes, giant clouds, and spurs/feathers, all in close geometrical association with shocked dust lanes. Despite observational and theoretical efforts during the past 15 years, what forms these secondary structures has still remained uncertain. In particular, do they require the presence of self-gravity or do they originate from non-gravitating hydrodynamic processes? In this talk, I will review the physical mechanisms proposed so far for the formation of the secondary structures, and report our resent work on the hydrodynamic instability of spiral shocks