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