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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20121108T103000
DTEND;TZID=Atlantic/Canary:20121108T113000
UID:iactalks-416
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/416
CREATED:2012-11-08T10:30:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Truncations in stellar disks and warps in HI-layers in spiral galax
 ies
DESCRIPTION:Truncations in stellar disks and warps in HI-layers in spiral g
 alaxies\nProf. Piet van der Kruit\n\nDisks in spiral galaxies consist of s
 tars and gas. The stellar disks  show radially an exponential surface brig
 htness distribution (and  vertically one resembling an isothermal sheet), 
 with relatively sharp  truncations at of order 4 scalelengths. These trunc
 ations are most  easily seen in edge-on galaxies. The evidence for these t
 runcations and  their statistics will be reviewed. Truncations appear to b
 e not only  truncations in the distribution of stars, but also in the tota
 l density.  The origin of these truncations seem related to the maximum sp
 ecific  angular momentum in the material that formed the disks. Disks are 
  extremely flat. The HI-gas often extends beyond the eructations in the  s
 tellar disks, but when they do they also show a warp. Again edge-on  galax
 ies show this mostly readily. Analysis shows that the warps start  abruptl
 y, just beyond the truncation radius and some other properties  also show 
 abrupt changes at the radius of the onset of the warp. This  suggests that
  warps are the result of infall of gas at later times, when  the formation
  of the stellar disks has been completed. The open issue  is still that we
  have not conclusively shown that we can discover the  face-on analogs of 
 the truncations we see in edge-on disk. I will  outline some recent resear
 ch I have been involved in and some ideas for  further work and collaborat
 ions.
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