Too Large and Overlooked?

1
Too Large and Overlooked?

• (Unexpected) Extended free-free emission towards
  massive star formation regions

Steven Longmore (Harvard-Smithsonian Center for
Astrophysics)
Michael Burton (UNSW), Eric Keto(CfA), Stan Kurtz
(UNAM), Andrew Walsh (JCU)
2
Talk aims

• Show results from Longmore et al 2009, MNRAS,
  399, 861
• What did we learn that may be relevant to
  planning a future ATCA survey for HCHIIs?

3
Hunting HCHIIs
4
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Learn to use your weapon effectively
• Don't be afraid to ask people more knowledgeable
  than you questions
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

5
Hunting HCHIIs
UCHII

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Learn to use your telescope effectively
• Don't be afraid to ask people more knowledgeable
  than you questions
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

HCHII
Astronomer
HII Region
Applying for telescope time
HCHII
ASTRO
6
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Learn to use your telescope effectively
• Don't be afraid to ask people more knowledgeable
  than you questions
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

7
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Learn to use your telescope effectively
• Don't be afraid to ask people more knowledgeable
  than you questions
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

8
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Learn to use your telescope effectively
• Don't be afraid to ask people more knowledgeable
  than you questions
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

9
A sample of HCHIIs?

• Initial sample of 100 IRAS selected objects
• Observe
• Thermal dust
• Methanol maser
• 8GHz continuum
• Select F8GHz lt 3mJy as pre-UCHII sample
• Thesis
• Found F24GHzgt50mJy towards 50 of pre-UCHII
  region objects
• From F24GHz/F8GHz postulated this could be sample
  of HCHIIs

10
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Don't be afraid to ask people more knowledgeable
  than you questions
• Learn to use your telescope effectively
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

11
Spatial filtering?

• However, array configs very different
• 8GHz ? 6A (6km baselines)
• 24GHz ? H168 (168m baselines)
• Sensitive to very different spatial scales
• Kurtz et al 1999
• Found extended emission around 12/15 UCHIIs
• Up to 5 (2pc)
• Up to an order of magnitude brighter than
  compact component

12
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Don't be afraid to ask people more knowledgeable
  than you questions
• Learn to use your telescope effectively
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

13
Observations

• Aim determine if objects are HCHIIs or extended
  emission?
• Get reliable SED
• 3 different frequencies
• 18GHz
• 35GHz
• 92GHz
• 3 different array configs matching beam sizes
• H75
• H168
• H214

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Results

• Interpretation of objects
• Confirmed HCHIIs
• - 8GHz optically-thick free-free
• - fall below pnt src sensitivity
• 2. Extended free-free emission
• - 8GHz optically-thin free-free
• - spatially extended
• - resolved-out at 8GHz
• 3. Outside primary beam
• Implications
• Misinterpret evolutionary stage
• 1/3 pre-uchii ? post-uchii
• Potentially underestimate dust masses by factor
  of two

15
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Don't be afraid to ask people more knowledgeable
  than you questions
• Learn to use your telescope effectively
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

16
What to take from this?

• In the hunt for HCHIIs
• Careful using interferometric continuum
  observations
• High resolution, snap-shot imaging with low
  number of antenna particularly susceptible to
  misinterpretting data

17
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Don't be afraid to ask people more knowledgeable
  than you questions
• Learn to use your telescope effectively
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

18
Hunting HCHIIs

• Top 10 hunting tips
• Attend a hunter safety/training course
• Learn all you can about what you are hunting
• Don't be afraid to ask people more knowledgeable
  than you questions
• Learn to use your telescope effectively
• Expect mistakes, and learn from them
• Spend as much time as you can out hunting
• Watch the wind
• Be still
• Be quiet
• Wear a safety harness each and every time you
  climb a tree

19
Thanks