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

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?

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)

Evolutionary Outline

Hot Core YSO UCHII OB Star

SED:Sub-mm Mid-IR Near-IR Visual

Masers:

CH3OH H2O OH

Radio:

No radio Weak Radio Strong Radio

High Resolution Observations

OVRO: 2.7mm 2 "

CO 4 "

S140 IRS 1

VLA 5 GHz

(1.4 GHz)

VLA 8 GHz

Tofani et al. (1995)

MERLIN 5 GHz 0.1"

2m speckle 0.2"

- 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)

Radio Proper Motions

5 year baseline 1 month baseline

Mid-IR Diffraction-Limited Imaging

S140 IRS 1, 2 & 3

- Subaru 24.5m, 0.6” resolution

- Fujiyoshi, Hoare, Moore

GL 989 Standard Star

24.5m images

Azimuthally-averaged profiles

24.5m 10.5m

Resolution of warm dust emission

• Models with r-2, r-1.5, r-1, r-0.5 density distribution

• Observations support steep density gradient

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

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

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

The MSX Galactic Plane Survey

• 8, 12, 14 and 21m, 18 resolution, |b|<5o

IRAS 12m MSX 8m MSX 21m

W75 N Region

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

+ OH/IR stars

+ C stars+ UCHII regions

+ PN

• Massive YSOs

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)

Radio Continuum

• 5 GHz, 1resolution at VLA & ATCA

• 1700 objects observed so farCompact H II Region Massive YSO candidate

Kinematic Distances

• 13CO at Mopra, Onsala, JCMT, PMO & GRS

• 1700 targets observed

Galactic Distribution

Resolving Distance Ambiguities with H I

Mid-IR

• 10m, 0.8resolution at UKIRT and ESO 3.6m, 350 objects observed + GLIMPSE

Near-IR

• K-band imaging at UKIRT & ANU 2.3m + 2MASS

• 400 targets observed

• H+K band spectroscopy at UKIRT

• 120 targets observed

Next Generation Plane Surveys

• Deeper and higher spatial resolution

• Complete wavelength coverage

• Common areas

• Matched sensitivities and resolutions

• The Spitzer 4-8m GLIMPSE legacy survey is the starting point (10o<l<65o, |b|<1o)

Survey Beam Sens. Region INT WFC H 0.7"

UKIDSS GPS J,H,K 0.7" 0.02mJy 15o<l<230o, |b|<5o

GLIMPSE 4-8 m 2" 1mJy 10o<l<65o, |b|<1o

MSX 8-21 m 20" 100mJy |b|<5o

ASTRO-F 50-200 m 30-50" 40?mJy all sky

Herschel 200-500 m 17-34" 20mJy |b|<2.5o?

SCUBA2 450/850 m 8-14" 4mJy 10o<l<250o, |b|<1o?

GRS 13CO 1-0 46" 0.4K 18o<l<54o, |b|<1o

HARP-B 13CO 3-2 15" 1K 10o<l<250o, |b|<1o?

CORNISH 5 GHz 1" 2 mJy 10o<l<65o, |b|<1o?

Proposed VLA Survey

• CORNISH Project (Hoare, Diamond, Churchwell, Kurtz, …)– CO-ordinated Radio ‘N’ Infrared Survey for High-mass

star formation

• 5 GHz, 1resolution 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

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

H II region

MYSO

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.

• 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