ami and massive star formation
DESCRIPTION
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: - PowerPoint PPT PresentationTRANSCRIPT
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School of somethingFACULTY OF OTHER
School of Physics & AstronomyFACULTY OF MATHEMATICS & PHYSICAL SCIENCES
AMI and Massive Star Formation
Melvin Hoare
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Evolutionary outline – High-mass
Object:
Molecular Core MYSO UCHII Hot Star
SED:
Sub-mm Mid-IR Near-IR Visual
Radio:
Undetected Weak Strong
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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, 1.5resolution (B configuration)
• Covers northern Spitzer GLIMPSE survey
• 10o<l<65o, |b|<1o
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Over-resolution of CORNISH HIIs
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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
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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)
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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
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• MYSOs display weak radio emission
• A few have been resolved to show jets
• Proper motions show velocities ~500 km s-1
Ionized Jets
Cep A2 (Patel et al. 2005)
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• Others show evidence of radiation driven disc wind
Disc winds
S140 IRS 1 (Hoare 2006)Drew, Proga & Stone (1998)
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Wind Spectra
Gibb & Hoare (2007)
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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
Jets Evolved OB stars Hoare & Franco (2007)
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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)
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Detection of winds by AMI
Non-detection by VLA 5 GHz <0.75 mJyDetection by AMI 16 GHz 1.8 mJy
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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