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Massive Young Stars in the Galaxy

Massive Young Stars in the Galaxy. Melvin Hoare University of Leeds UK. Outline. Introduction Massive YSOs High resolution observations The RMS Survey Galaxy-wide survey for massive YSOs Next generation galactic plane surveys UKIDSS GPS, SCUBA2, CORNISH Conclusions.

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Massive Young Stars in the Galaxy

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  1. Massive Young Stars in the Galaxy Melvin Hoare University of Leeds UK

  2. Outline • Introduction • Massive YSOs • High resolution observations • The RMS Survey • Galaxy-wide survey for massive YSOs • Next generation galactic plane surveys • UKIDSS GPS, SCUBA2, CORNISH • Conclusions

  3. Massive Star Formation • What determines the upper IMF? • The physics of infall • Turbulence? • Magnetic fields? • Dynamics? • The physics of outflow • Radiation pressure on dust? • Radiation pressure on gas? • MHD driven flows?

  4. Massive Young Stellar Objects • Luminous (>104 L¤), embedded IR source • Bipolar molecular outflow • Often has associated maser emission • Compact, ionised wind (v~100 km s-1)

  5. Evolutionary Outline Hot Core à YSO à UCHII à OB Star SED: Sub-mm à Mid-IR à Near-IR à Visual Masers: CH3OH à H2O à OH Radio: No radio à Weak Radio à Strong Radio

  6. High Resolution Observations S140 IRS 1 OVRO: 2.7mm 2 " CO 4 "

  7. VLA 5 GHz (1.4 GHz)

  8. VLA 8 GHz Tofani et al. (1995)

  9. MERLIN 5 GHz 0.1" 2mm speckle 0.2"

  10. Monopolar reflection nebula in a massive YSO • Scattered light in blueshifted outflow lobe • Polarimetry confirms scattered nature of extended emission S140 IRS 1 Schertl et al (2000)

  11. Radio Proper Motions 5 year baseline 1 month baseline

  12. Mid-IR Diffraction-Limited Imaging - Subaru 24.5mm, 0.6” resolution - Fujiyoshi, Hoare, Moore S140 IRS 1, 2 & 3

  13. 24.5mm images GL 989 Standard Star

  14. Azimuthally-averaged profiles 24.5mm 10.5mm

  15. Resolution of warm dust emission • Models with r-2, r-1.5, r-1, r-0.5 density distribution • Observations support steep density gradient

  16. Mm Interferomety • Resolution of the cool dust continuum emission from the envelope • ATCA mm interferometer • 5 x 22m dishes and 128 MHz bandwidth • Hoare, Urquhart, Gibb, in prep

  17. MYSO Samples • Well characterised MYSOs number in the tens • Not systematically found and mostly nearby • May not be representative • Need well-selected sample that number in the hundreds • Can then study properties in a statistically robust way

  18. Surveys for MYSOs • Too obscured in near-IR • Radio continuum too weak • No single maser transition always present • Molecular cores do not necessarily contain YSOs • Need to use IR where bulk of energy emerges • IRAS-based searches suffer from confusion

  19. The MSX Galactic Plane Survey • 8, 12, 14 and 21mm, 18² resolution, |b|<5o W75 N Region IRAS 12mm MSX 8mm MSX 21mm

  20. The Red MSX Source (RMS) Survey • Colour-select massive YSO candidates from the MSX Point Source Catalogue and 2MASS near-IR survey • Delivers ~2000 candidates • Many other object types with similar near- and mid-IR colours

  21. • Massive YSOs + UCHII regions + C stars + OH/IR stars + PN

  22. Multi-wavelength Ground-based Follow-up Campaign • Identify and eliminate confusing sources • Begin characterisation of the massive YSOs • RMS Team: • Stuart Lumsden, Rene Oudmaijer, James Urquhart, Ant Busfield, Tamara King, Andrew Clarke (Leeds, UK) • Toby Moore, James Allsopp (Liverpool JMU, UK) • Cormac Purcell, Michael Burton (UNSW, Australia) • Zhibo Jiang, Wang Min (PMO, China)

  23. Radio Continuum • 5 GHz, 1² resolution at VLA & ATCA • 1700 objects observed so far Compact H II Region Massive YSO candidate

  24. Kinematic Distances • 13CO at Mopra, Onsala, JCMT, PMO & GRS • 1700 targets observed

  25. Galactic Distribution

  26. Resolving Distance Ambiguities with H I

  27. Mid-IR • 10mm, 0.8² resolution at UKIRT and ESO 3.6m, 350 objects observed + GLIMPSE

  28. Near-IR • K-band imaging at UKIRT & ANU 2.3m + 2MASS • 400 targets observed • H+K band spectroscopy at UKIRT • 120 targets observed

  29. Next Generation Plane Surveys • Deeper and higher spatial resolution • Complete wavelength coverage • Common areas • Matched sensitivities and resolutions • The Spitzer 4-8mm GLIMPSE legacy survey is the starting point (10o<l<65o, |b|<1o)

  30. Proposed VLA Survey • CORNISH Project (Hoare, Diamond, Churchwell, Kurtz, …) • CO-ordinated Radio ‘N’ Infrared Survey for High-mass star formation • 5 GHz, 1² resolution B configuration VLA survey of the northern GLIMPSE region • 9000 pointings of 2 minutes each requiring 400 hours in total • 2 mJy 50% completeness limit

  31. CORNISH Science • Unbiased census of UCHII regions • Triggering and clustering of massive star formation • Identification of radio loud/quiet objects found in GLIMPSE • UCHII regions/Massive YSOs • PN/Proto-PN • Be stars, WR stars, active binaries, X-ray sources etc. • Legacy science

  32. ·H II region ¡MYSO

  33. Conclusions • High resolution observations are beginning to resolve the envelope and winds • The RMS survey will deliver ~1000 massive YSOs over the whole galaxy • GLIMPSE, in combination with other surveys, will deliver very large numbers of intermediate mass YSOs right across the inner galaxy.

  34. Large well-selected samples for future high resolution studies e.g. 8m, ALMA, SKA • The combination of GLIMPSE and UKIDSS GPS will be particularly powerful for YSO, evolved star and stellar population studies • Future SCUBA2, HERSCHEL and CORNISH surveys will be excellent tools for systematic massive star formation studies

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