AMI and Massive Star Formation
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Transcript of AMI and Massive Star Formation
School of somethingFACULTY OF OTHER
School of Physics & AstronomyFACULTY OF MATHEMATICS & PHYSICAL SCIENCES
AMI and Massive Star Formation
Melvin Hoare
Evolutionary outline – High-mass
Object:
Molecular Core MYSO UCHII Hot Star
SED:
Sub-mm Mid-IR Near-IR Visual
Radio:
Undetected Weak Strong
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
Over-resolution of CORNISH HIIs
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
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)
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
• 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)
• Others show evidence of radiation driven disc wind
Disc winds
S140 IRS 1 (Hoare 2006)Drew, Proga & Stone (1998)
Wind Spectra
Gibb & Hoare (2007)
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)
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)
Detection of winds by AMI
Non-detection by VLA 5 GHz <0.75 mJyDetection by AMI 16 GHz 1.8 mJy
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