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AMI and Massive Star Formation

School of Physics & Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES. AMI and Massive Star Formation. Melvin Hoare. Evolutionary outline – High-mass. Object: Molecular Core à MYSO à UCHII à Hot Star SED: Sub-mm à Mid-IR à Near-IR à Visual Radio:

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AMI and Massive Star Formation

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  1. School of Physics & Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES AMI and Massive Star Formation Melvin Hoare

  2. Evolutionary outline – High-mass Object: Molecular Core à MYSO à UCHII à Hot Star SED: Sub-mm à Mid-IR à Near-IR à Visual Radio: Undetected à Weak à Strong

  3. Radio Survey for UCHII regions • The Co-Ordinated Radio ‘N’ Infrared Survey for High-mass star formation or CORNISH survey • High spatial resolution VLA survey of the Galactic Plane • 5 GHz, 1.5² resolution (B configuration) • Covers northern Spitzer GLIMPSE survey • 10o<l<65o, |b|<1o

  4. Over-resolution of CORNISH HIIs

  5. Over-resolution/snapshot VLA B config 15 GHz snapshot Integrated flux 2.6 Jy VLA D config 15 GHz observation Integrated flux 3.9 Jy

  6. Ionizing Star(s) Spectral Type • Correct optically thin, integrated radio flux is crucial to determine the ionizing flux and hence spectral type of the ionizing star(s)

  7. Massive Young Stellar Objects • Luminous (>104 L¤) embedded IR point source • no UCHII region - star swollen due to ongoing accretion? • bipolar molecular outflow (~10 km s-1) • ionised wind (~100 km s-1) GL 2591

  8. Ionized Jets • MYSOs display weak radio emission • A few have been resolved to show jets • Proper motions show velocities ~500 km s-1 Cep A2 (Patel et al. 2005)

  9. Disc winds • Others show evidence of radiation driven disc wind S140 IRS 1 (Hoare 2006) Drew, Proga & Stone (1998)

  10. Wind Spectra Gibb & Hoare (2007)

  11. Radio vs IR luminosity • Clear distinction between UCHIIs and MYSOs at luminous end • MYSOs also distinguished from OB star winds – MS OB stars not detected yet Hoare & Franco (2007) ¨ Jets p Evolved OB stars

  12. Red MSX Source Survey • sample of about 500 MYSOs from mid-IR survey and ground-based follow-up • e-Merlin Legacy programme to detect and map the winds/jets for sub-sample of 75 of these • ongoing near-IR spectroscopy programmes to study H I emission line profiles which constrain outflow velocity • study the ionized feedback as a function of stellar mass (luminosity) and age (embeddedness)

  13. Detection of winds by AMI Non-detection by VLA 5 GHz <0.75 mJy Detection by AMI 16 GHz 1.8 mJy

  14. Summary • AMI can play a useful role following-up 100s of: • CORNISH UCHII regions for spectral typing ionizing star(s) • RMS MYSOs for (pre-) detecting wind/jet emission, although really need resolution of EVLA to be sure of detection and e-Merlin to actually resolve the emission

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