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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20100204T000000
DTEND;TZID=Atlantic/Canary:20100204T010000
UID:iactalks-155
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/155
CREATED:2010-02-04T00:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Electron densities in HII regions across galaxy discs
DESCRIPTION:Electron densities in HII regions across galaxy discs\nProf. Jo
 hn E. Beckman\n\nWhen we measure the electron density within an H II regio
 n using ratios of emission lines we find characteristic values in the rang
 e of 100-300 cm-3. But when we make these measurements using the total lum
 inosity in Hα and the overall radial size of an H II region we find 
 average values in the range 3-10. I will first explain how this discrepanc
 y occurs, and then go on to show some measurements of electron densities i
 n the H II regions of M51 (over 2500 regions) and the dwarf galaxy NGC 444
 9 (over 250 regions) using the second method, by Leonel Gutiérrez and mys
 elf. From these measurements we can infer how the electron density varies 
 with the radial size of an individual region, and how it varies as we move
  from the center of the galaxy disc to the outside. Some interesting simpl
 e global relationships are found, which tell us about the interaction of s
 tar forming regions with their surroundings and how this interaction varie
 s across the face of a galaxy.\n\n
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