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DTSTART;TZID=Atlantic/Canary:20100324T000000
DTEND;TZID=Atlantic/Canary:20100324T010000
UID:iactalks-40
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/40
CREATED:2010-03-24T00:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Study of molecular clouds associated with HII regions
DESCRIPTION:Study of molecular clouds associated with HII regions\nDr. Moha
  Azimlu\n\nThe properties of molecular clouds associated with 10 H II regi
 ons were studied using CO observations.  We identified 142 dense clumps wi
 thin our sample and measured and calculated  physical properties of the cl
 umps such as size, excitation temperature, line widths, density and mass. 
 We found  that our sources are divided  into two  categories: those that s
 how a size-line width relation ("type I")  and those which do not show any
  relation ("type II"). Type II  sources have larger line widths in general
 . Investigating  the relation between the line width and other parameters 
 shows that while the MLTE (Local Thermodynamic Equilibrium mass) increases
  with ΔV  (line width) for both  12CO(2-1) and  13CO(2-1) lines in t
 ype I sources,  no  relation  was found for type II sources. No relation b
 etween column density and  line width was found for either  category.  We 
 also investigated how the characteristics of the clumps vary with distance
  from the HII region. We found no relation between mass distribution of th
 e clumps and distance from the ionization front, but a weak decrease of th
 e excitation temperature with increasing distance from the ionized gas.  O
 nly the projected distance is measured in our study  which is equal or sma
 ller than the true value.  Therefore we compared the results by a Monte Ca
 rlo  simulation of a central heating source and found that for small dista
 nces the relation is very scattered, which is consistent with our results.
   No  relation was found  between line width and distance from the H II re
 gion which probably  indicates that the internal dynamics of the clumps is
  not affected by the ionized gas.  Internal sources of turbulence, such as
  outflows and stellar winds from young proto-stars may have a more importa
 nt role.
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