1 / 12

Model fitting AT20G ultra/hyper compact HII region visibilities and the nature of the 3mm excess

Model fitting AT20G ultra/hyper compact HII region visibilities and the nature of the 3mm excess. Ron Ekers CSIRO Sydney, Sep 8, 2010. Sample selection – AT20G (20GHz) AT20G Galactic plane region (|b| < 1.5 o ) Blind survey S 20 GHz > 200 mJy 263 sources

sidney
Download Presentation

Model fitting AT20G ultra/hyper compact HII region visibilities and the nature of the 3mm excess

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Model fitting AT20G ultra/hyper compact HII region visibilities and the nature of the 3mm excess Ron Ekers CSIRO Sydney, Sep 8, 2010

  2. Sample selection – AT20G (20GHz) AT20G Galactic plane region (|b| < 1.5o) Blind survey S 20 GHz > 200 mJy 263 sources Sample selection - MGPS-2 (0.843 GHz) Compact in AT20G and MPGS-2 Isolated in AT20G and MGPS-2 Inverted spectrum (α 0.8-20GHz > 0.1) 46 sources Murphy et al. 2010, MNRAS, 405, 1560 Galactic Ron Ekers

  3. Hyper Compact HII region G330-00 • Ne 1.6x105 • Size 0.05pc • EM 1.3 109 • Te 104 K • Low freq excess • 3mm excess Ron Ekers

  4. Compact galactic sourcesfree-free emission models Name TeSize EM Ne95/45 Class (K) (pc) (pc cm-6) GHz G301.1366−00.2248 11600 0.02 3.0E+09 6.8E+05 ... H G302.0321−00.0606 8000 0.14 3.0E+07 1.5E+04 1.6 U G307.5604−00.5875 7100 0.30 5.0E+06 4.1E+03 ... U G309.9217+00.4788 6700 0.03 8.0E+08 2.3E+05 2.0 H G323.4594−00.0788 8100 0.05 1.9E+08 6.4E+04 2.9 H G328.8076+00.6330 6400 0.25 6.0E+07 1.6E+04 2.5 U G330.9536−00.1820 10400 0.05 1.3E+09 1.6E+053.5 H G332.8254−00.5499 6500 0.06 4.0E+08 8.0E+04 1.8 U Ron Ekers

  5. G330 – UC/HC HII Ron Ekers

  6. G330 – 19GHz 2.9” 5Jy G330 – ATCA Visibility Visibility amplitude (Jy) Spacing (kλ ) Ron Ekers

  7. SED model fitting • Simple constant density free-free emission model • Flux densities at 0.8, 19, 32, 44, 95 GHz • Visibilities (angular sizes) at 19, (32, 44, 95) GHz • Assume Te from recomb line • 19GHz point gives EM and SED • predicts all other frequencies • 0.8 GHz always high • needs an optically thin large component • 19, 32, 44 GHz usually fit • 95 GHz often high Ron Ekers

  8. G330: 1x free-free • Fit EM at 19 GHz Ron Ekers

  9. G330: 2x free-free • Fit 0.8GHz Ron Ekers

  10. G330: free-free + dust • Add dust • Has to be very hot Ron Ekers

  11. G330: ν+1 spectrum ? • ν+1 ? Ron Ekers

  12. G309 – ATCASize v Frequency • 20GHz 0.9” • 40GHz 1.0” • 95GHz 0.8” • Getting the high frequency flux from the same size is a problem because it has to be optically thick at lower frequencies • Easiest way to do this is to make filling factor <<1 • Hierarchical model • Shell models • Note that the 0.8 GHz point can’t be fit in the same model Ron Ekers

More Related