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Lientjie de VilliersPhD Supervisor: Dr. M.A. Thompson
University of Hertfordshire
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Methanol masers and the 6.7 GHz methanol maser surveyMolecular outflowsHARP instrument on the JCMTData reduction processResults:
outflow detection script3D representation and possible outflows3D overlay of different molecular emissons
Future work:Expand data from other surveys – Galactic planeMedical imaging analysis
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Maser = Microwave Amplification by Stimulated Emission of RadiationTrace an IR bright stage immediately prior to development of UC HII regions1 ~ 104 year# molecules in quantum state 2 = n2
state 1 = n1 If n2/n1 > 1 population inversion due to radiative pumping MASER.
2 Classes2 :Class I – collisionally pumped, often associated with outflowsClass II - radiatively pumped – far IR emission by dust cocoon around the maser, uniquely associated with high mass star formation 3,4,5
Class II methanol masers: brightest radio sources in sky, & compact.Galaxy = transparent at 6.67 GHz ideal tracers for star formation in Galactic structure.
1 Codella et al. 2004; 2. Sobolev et al. 2005; 3. Sobolev et al. 1997; 4.Minier et al. 2003; 5. Ellingsen, 2005
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Outflowing wind > vsound from protostar – accelerate surrounding molecular gas to vmg >> vcloud of quiescent cloud gas produce molecular outflow, a turbulent expanse of cloud gas from the vicinity of a stellar sourcePart of the SF process mass-loss phase during their protostellar stages 1
1 Arce et al. 2007
Search for outflows associated with methanol masers – the latter always associated with high mass SF its dynamic lifetime = upper bound on maser lifetimeDe Buizier (2009) observed the SiO (6-5) transition of 10 maser sources. Broad line wings indicate outflows all the sources with bright SiO lines, displayed broad line wings indicitave of outflow.
Not finally confirmed.
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Heterodyne Array Receiver Program 16 pix heterodyne focal-plane array receiver
4x4 element array with SIS detectors
Beam size 14” @ 345 GHz
High 3D mapping speed
sensitivity at 325-375 GHz
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Selection from a HARP-B outflow survey of 200 Class II methanol masers drawn from MMB catalogue of 6.7 GHz (4.49 cm) masers.13CO J=3-2 (trace outflows) C18O J=3-2 (see core)
Masers selected with wide range of luminosities, distances and galactic longitudes analyse differences in outflow properties.
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Starlink’s NAMAKA version of the REDUCE SCIENCE PIPELINE
Raw timeseries image
~ Clip noisy ends~ Sub 1 baseline Bl. Subtracted
timeseries
Clumpfind baseline mask
3 baseline fit on timeseries
Pipeline reduced cube
~ Sub 3 baselline~ Makecube
Collapse along velocity axis – quality control
Collapsed image
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~ Clip noisy ends~ Sub 1 baseline Bl. Subtracted
timeseries
Clumpfind baseline mask
3 baseline fit on timeseries
~ Sub 3 baselline~ Makecube
Collapsed along v over (peak-20km/s; peak+20 km/s)RA
Dec
Receptor #
Tim
e
Example: 13CO images from Maser source G30.704 -0.06
RA
Dec
CUBE COLLAPSED CUBEMore edge clippingDespikeRebin velocitySwitch of noisy receptors
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Aim of this phase:
Simple outflow detection & contour mapping
3D image rendering with current astronomical software (GAIA) of both 13CO and C18O.
Detect outflows in 3D by eye
Create a 3D training set for future medical image analysis programs
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Simple outflow detection method1:Using median filter: determine central v and width of source peakDerive from above: define BLUE = (-10 ; -2) GREEN = (-2; 2) RED = (2; 10)
1. Private communication: Antonio Chrysostomou – JAC, Hawaii
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Simple outflow detection method1:Using median filter: determine central v and width of source peakDerive from above: define BLUE = (-10 ; -2) GREEN = (-2; 2) RED = (2; 10)Create 3 separate images by collapsing over above regions.
1. Private communication: Antonio Chrysostomou – JAC, Hawaii
Example: 13CO image from Maser source G30.760 -0.05
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Example: 13CO image from Maser source G30.760 -0.05
3D rendering
in Gaia
3 separation between contours (receptor temp). Levels: 6.6 K; 4.3 K, 2.1 K
Blue: 13CO; Yellow: C18O; Plane: image plane located at central peak velocity
C18O : abundance thus opacity see core
13CO > abundant than C18O, see more structure like
outflows. Both molecules low enough density & low
opacity – trace dense gas in molecular cores where masers are embedded.
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Another example of high velocity structures (possible outflows?)
Contours and 3D rendering of 13CO and C18O images of G24.790 +0.08
However, still inconclusive, need to be confirmed.
3 separation between contours (receptor temp). Levels: 6.1 K; 3.8 K, 1.5 K
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Expand dataExpand current data set of 80 sources with 13CO and C18O maser observations from T. MooreGet 12CO images for all maser sources from 12CO galactic plane survey (JAC)
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Investigate Medical Imaging optionsOutflows = irregular 3D shapes similarities with typical medical imaging problemsArce et al. (2010) visualized the molecular clouds from Perseus 3D in Ra-Dec-v space detected high velocity features (e.g. outflows)Used 3D Slicer from MIT Artificial Intelligence Lab & Surgical Planning Lab at Brighham and Women’s Hospital designed to help surgeons in image-guided surgery, diagnostics and brain research visualization.1
1. Borkin et al. 2005
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“If the whole universe has no meaning, we should never have found out that it has no meaning: just as, if there were no light in the universe and therefore no creatures with eyes, we should never know it was dark. Dark would be without meaning.”
C.S. Lewis