A Galaxy-wide Sample of Massive Young Stellar Objects · School of Physics and Astronomy FACULTY OF...
Transcript of A Galaxy-wide Sample of Massive Young Stellar Objects · School of Physics and Astronomy FACULTY OF...
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School of Physics and AstronomyFACULTY OF MAPS
A Galaxy-wide Sample of Massive Young Stellar Objects
James Urquhart RMS Team:
Melvin Hoare, Stuart Lumsden, René Oudmaijer, Ant Busfield, Andrew Clarke, Joseph Mottram, Joseph Stead (Leeds)Toby Moore (Liverpool JMU)Cormac Purcell (Jodrell Bank)Michael Burton (UNSW)Zhibo Jiang (PMO)
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School of Physics and AstronomyFACULTY OF MAPS
The Red MSX Source (RMS) Survey
James Urquhart
RMS Team:Melvin Hoare, Stuart Lumsden, René Oudmaijer, Ant Busfield, Andrew Clarke, Joseph Mottram, Joseph Stead (Leeds)Toby Moore (Liverpool JMU)Cormac Purcell (Jodrell Bank)Michael Burton (UNSW)Zhibo Jiang (PMO)
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• Introduction• Colour selection of MYSOs• Follow-up programme • Progress and initial results• Summary • Future programmes
The RMS SurveyTalk Outline
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• Mid and Near-IR bright• Luminous (>104 Lo)• Radio quiet → UCHII region has not
formed• Often associated maser emission• Bipolar molecular outflow → accretion is
still taking place
MotivationWhat is a MYSO?
GL2591:Gemini JHK
B-type MYSO (see poster by K. Johnston #47)
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MotivationMYSO samples
• Well characterised MYSOs number in the tens• Not systematically found and mostly nearby• Most samples IRAS colour selected:‣ Bias towards bright isolated sources‣ tend to avoid dense clustered environments and the Galactic mid-
plane where majority of MYSOs are expected - scale height massive stars ~30’ (Reed 2000)
• The limited number and selection method means they may not be representative of the general population of MYSOs
• Need well-selected sample that number in the hundreds• Can then study properties in a statistically robust way
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MotivationSearching 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
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The RMS SurveyColour Selection of MYSOs
• MSX survey: 8, 12, 14 and 21µm, 18″ resolution, |b|<5o
• Colour-select massive YSO candidates from the MSX PSC and 2MASS near-IR survey (Lumsden et al. 2002)
• Delivers ~2000 candidates• Many other object types with similar near- and mid-IR colours
IRAS 12µm MSX 8µm MSX 21µm
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The RMS SurveyColour Selection of MYSOs
• MSX survey: 8, 12, 14 and 21µm, 18″ resolution, |b|<5o
• Colour-select massive YSO candidates from the MSX PSC and 2MASS near-IR survey (Lumsden et al. 2002)
• Delivers ~2000 candidates• Many other object types with similar near- and mid-IR colours
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The RMS SurveyColour Selection of MYSOs
• Massive YSOs + UCHII regions+ PN
+ C stars+ OH/IR stars
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Multi-wavelength follow-up campaignObservational Programme
• Identify and eliminate confusing sources• Begin characterisation of the massive YSOs• Observational programme includes• Mid-IR imaging (UKIRT, Gemini)• Radio continuum (VLA & ATCA)• Molecular lines (13CO and CS; Mopra, JCMT, PMO, Onsala, FCRAO)• Near-IR imaging and spectroscopy (AAT, UKIRT, NTT)
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Multi-wavelength follow-up campaignRadio Continuum
Radio Continuum• Identify UCHII regions and small number of PNe• 5 GHz, 2″ resolution, 0.3 mJy/beam noise level at VLA & ATCA• 2000 objects observed (Urquhart et al. 2007)• ~25% of sources detected in radio• Morphologies, distribution and spectral indices consistent with these sources
being identified as UCHII regions
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Multi-wavelength follow-up campaignMid-IR Imaging
• 10µm, 0.8″ resolution at 700 objects observed & GLIMPSE
• Distinguish between UCHII regions and MYSOs
‣ UCHII → Extended
‣ MYSO → Point like
•Mid-IR imaging complements radio imaging in cases where UCHII and MYSOs are in close proximity
•See Mottram et al. 2007 (astro-ph/0709.2040)
G293.9512-00.8941
G287.4373-00.6129
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Multi-wavelength follow-up campaignMillimetre Line Observations
• Obtain kinematic distances• Identify nearby low-luminosity YSOs,
evolved stars (~200)• 2000 sources observed - complete• Using Brand and Blitz (1993) rotation
curve• Two difficulties:• Multiple components towards many
sources (~50%)• Masers + CS
• Most sources (80%) are located within the solar circle i.e. distance ambiguities!• HI Self-absorption (IGPS)
• See Busfield et al. 2006
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Multi-wavelength follow-up campaignNear-IR Imaging and Spectoscopy
• Identify remaining evolved stars and confirm identified MYSOs
• K-band imaging + 2MASS• 400 targets observed • H+K band spectroscopy• ~250 targets observed
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Preliminary ResultsSource Identification
0
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YSO
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Preliminary ResultsGalactic Distribution MYSOs + UCHII
Rotation curve fromBrand and Blitz 1993Spiral arm structure fromCordes & Lazio 2004
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Preliminary ResultsLuminosity Distribution
Luminosities have been estimated using the IRAS fluxes (i.e. Emerson 1988)
See poster by J. Mottram #71
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The RMS SurveySummary
• The RMS survey will deliver ~500 massive YSOs over the whole galaxy
• In addition will identify ~500 compact and UCHII regions• Luminosity function of MYSOs and UCHIIs• Investigate triggering and clustering as a function of Galactic location• High spatial/spectral resolution studies of well-selected sub-samples
for infall, accretion and outflow characteristics• Sample will be available at www.ast.leeds.ac.uk/RMS
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The RMS SurveyFurther Work
• Broadband chemical study of distance limited sample of MYSO• Outflow studies (Mopra and JCMT)• Accretion disks (VLTI, Gemini)• Search for associated water masers and ammonia studies (Mopra)• Studies of potentially triggered regions (IRAM 30m + CARMA)
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The RMS SurveyDistribution of RMS Sources
Northern Galactic Plane
Southern Galactic Plane
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Multi-wavelength follow-up campaignGLIMPSE 8µm + 6cm radio contours
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Preliminary ResultsLongitude-Velocity Distribution
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Preliminary ResultsLongitude-Latitude Distribution
Northern Galactic Plane
Southern Galactic Plane
Dame et al. 2001
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Multi-wavelength follow-up campaignSolving Distance Ambiguities
Use HI data from the IGPS and the HI self-absorption methode.g. Jackson et al. 2002 & Kolpak et al. 2003
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The RMS SurveyFuture programmes
• Luminosity function of MYSOs and UCHIIs• Investigate triggering and clustering as a function of Galactic location• High spatial/spectral resolution studies of well-selected sub-samples
for infall, accretion and outflow characteristics
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The RMS SurveyStatistical Studies
• Luminosity function of MYSOs and UCHIIs (RG, environment)
• Lifetime of MYSO phase (L)• Clustering of MYSOs and UCHIIs• Triggering by UCHIIs, OB stars, SNRs
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Preliminary ResultsLongitude-Velocity Distribution
Northern Galactic Plane
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The RMS SurveyMulti-wavelength follow-up campaign
Southern Galactic Plane
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School of Physics and AstronomyFACULTY OF MAPS
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Multi-wavelength follow-up campaignExample Spectra
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