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Massive Young Stars in the Galaxy

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Luminous ( 104 L ), embedded IR source. Bipolar molecular outflow ... MERLIN 5 GHz 0.1' 2mm speckle 0.2' Monopolar reflection nebula in a massive YSO ... – PowerPoint PPT presentation

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Title: Massive Young Stars in the Galaxy


1
Massive Young Stars in the Galaxy
  • Melvin Hoare
  • University of Leeds
  • UK

2
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

3
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?

4
Massive Young Stellar Objects
  • Luminous (gt104 L), embedded IR source
  • Bipolar molecular outflow
  • Often has associated maser emission
  • Compact, ionised wind (v100 km s-1)

5
Evolutionary Outline
  • Hot Core à YSO à UCHII à OB Star
  • SED
  • Sub-mm à Mid-IR à Near-IR à Visual
  • Masers
  • CH3OH à H2O à OH
  • Radio
  • No radio à Weak Radio à Strong Radio

6
High Resolution Observations
S140 IRS 1
OVRO 2.7mm 2 " CO 4 "
7
VLA 5 GHz (1.4 GHz)
8
VLA 8 GHz Tofani et al. (1995)
9
MERLIN 5 GHz 0.1" 2mm speckle 0.2"
10
  • 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)
11
Radio Proper Motions
5 year baseline
1 month baseline
12
Mid-IR Diffraction-Limited Imaging
- Subaru 24.5mm, 0.6 resolution - Fujiyoshi,
Hoare, Moore
S140 IRS 1, 2 3
13
24.5mm images
GL 989
Standard Star
14
Azimuthally-averaged profiles
24.5mm
10.5mm
15
Resolution of warm dust emission
  • Models with r-2, r-1.5, r-1, r-0.5 density
    distribution
  • Observations support steep density gradient

16
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

17
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

18
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

19
The MSX Galactic Plane Survey
  • 8, 12, 14 and 21mm, 18² resolution, blt5o

W75 N Region
IRAS 12mm
MSX 8mm
MSX 21mm
20
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

21
Massive YSOs
C stars
UCHII regions
OH/IR stars
PN
22
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)

23
Radio Continuum
  • 5 GHz, 1² resolution at VLA ATCA
  • 1700 objects observed so far

Compact H II Region
Massive YSO candidate
24
Kinematic Distances
  • 13CO at Mopra, Onsala, JCMT, PMO GRS
  • 1700 targets observed

25
Galactic Distribution
26
Resolving Distance Ambiguities with H I
27
Mid-IR
  • 10mm, 0.8² resolution at UKIRT and ESO 3.6m, 350
    objects observed GLIMPSE

28
Near-IR
  • K-band imaging at UKIRT ANU 2.3m 2MASS
  • 400 targets observed
  • HK band spectroscopy at UKIRT
  • 120 targets observed

29
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30
Next Generation Plane Surveys
  • Deeper and higher spatial resolution
  • Complete wavelength coverage
  • Common areas
  • Matched sensitivities and resolutions
  • The Spitzer 4-8mm GLIMPSE legacy survey is the
    starting point (10oltllt65o, blt1o)

31
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32
Proposed VLA Survey
  • CORNISH Project (Hoare, Diamond, Churchwell,
    Kurtz, )
  • CO-ordinated Radio N Infrared Survey for
    High-mass star formation
  • 5 GHz, 1² resolution 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

33
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

34
H II region MYSO
35
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.

36
  • 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
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