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. Top 10 hunting tips 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Learn to use your weapon effectively 4.Don't be afraid to ask people more knowledgeable than you questions 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.Wear a safety harness each and every time you climb a tree

5. Hunting HCHIIs Applying for telescope time HCHII UCHII HCHII Astronomer HII Region ASTRO Top 10 hunting tips 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Learn to use your telescope effectively 4.Don't be afraid to ask people more knowledgeable than you questions 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.Wear a safety harness each and every time you climb a tree

6. Hunting HCHIIs Top 10 hunting tips 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Learn to use your telescope effectively 4.Don't be afraid to ask people more knowledgeable than you questions 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.Wear a safety harness each and every time you climb a tree

7. Hunting HCHIIs Top 10 hunting tips 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Learn to use your telescope effectively 4.Don't be afraid to ask people more knowledgeable than you questions 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.Wear a safety harness each and every time you climb a tree

8. Hunting HCHIIs Top 10 hunting tips 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Learn to use your telescope effectively 4.Don't be afraid to ask people more knowledgeable than you questions 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.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 F 8GHz < 3mJy as pre- UCHII sample Thesis –Found F 24GHz >50mJy towards 50% of pre-UCHII region objects –From F 24GHz /F 8GHz postulated this could be sample of HCHIIs

10. Hunting HCHIIs Top 10 hunting tips 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Don't be afraid to ask people more knowledgeable than you questions 4.Learn to use your telescope effectively 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.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 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Don't be afraid to ask people more knowledgeable than you questions 4.Learn to use your telescope effectively 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.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 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Don't be afraid to ask people more knowledgeable than you questions 4.Learn to use your telescope effectively 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.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 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Don't be afraid to ask people more knowledgeable than you questions 4.Learn to use your telescope effectively 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.Wear a safety harness each and every time you climb a tree

18. Hunting HCHIIs Top 10 hunting tips 1.Attend a hunter safety/training course 2.Learn all you can about what you are hunting 3.Don't be afraid to ask people more knowledgeable than you questions 4.Learn to use your telescope effectively 5.Expect mistakes, and learn from them 6.Spend as much time as you can out hunting 7.Watch the wind 8.Be still 9.Be quiet 10.Wear a safety harness each and every time you climb a tree

19. Thanks