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Too Large and Overlooked?

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). Talk aims.

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Too Large and Overlooked?

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  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 < 3mJy as pre-UCHII sample • Thesis • Found F24GHz>50mJy 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

  14. Results • Interpretation of objects • Confirmed `HCHII’s: • - 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

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