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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20090324T000000
DTEND;TZID=Atlantic/Canary:20090324T010000
UID:iactalks-55
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/55
CREATED:2009-03-24T00:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Spirals and rings: how do they form? What are their structure and p
 roperties?
DESCRIPTION:Spirals and rings: how do they form? What are their structure a
 nd properties?\nDr. Lia Athanassoula\n\nI will propose a new theory to exp
 lain the formation and properties of rings and spirals in barred galaxies,
  focusing on a comparison of theoretical results to observations and givin
 g some predictions for further comparisons. This theory can account for bo
 th spirals and rings, the latter both inner and outer. The model outer rin
 gs have the observed R1, R_1', R_2, R_2' and  R_1R_2 morphologies, includi
 ng the dimples near the direction of the bar major axis. It explains why t
 he vast majority of spirals in barred galaxies are two armed and trailing 
 and I will discuss what it takes for higher multiplicity arms to form. The
  shapes of observed and theoretical spirals agree and the theory predicts 
 that stronger non-axisymmetric forcings at and somewhat beyond corotation 
 will drive more open spirals. I will compare the ratio of ring diameters i
 n theory and in observations and predict that more elliptical rings will c
 orrespond to stronger forcings. This theory also provides the right buildi
 ng blocks for the rectangular-like bar outline and for ansae.
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