Presentation on theme: "Lientjie de Villiers PhD Supervisor: Dr. M.A. Thompson University of Hertfordshire."— Presentation transcript:
Lientjie de Villiers PhD Supervisor: Dr. M.A. Thompson University of Hertfordshire
Methanol masers and the 6.7 GHz methanol maser survey Molecular outflows HARP instrument on the JCMT Data reduction process Results: outflow detection script 3D representation and possible outflows 3D overlay of different molecular emissons Future work: Expand data from other surveys – Galactic plane Medical imaging analysis
Maser = Microwave Amplification by Stimulated Emission of Radiation Trace an IR bright stage immediately prior to development of UC HII regions 1 ~ 10 4 year # molecules in quantum state 2 = n 2 state 1 = n 1 I f n 2 /n 1 > 1 population inversion due to radiative pumping MASER. 2 Classes 2 : Class I – collisionally pumped, often associated with outflows Class 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
Outflowing wind > v sound from protostar – accelerate surrounding molecular gas to v mg >> v cloud of quiescent cloud gas produce molecular outflow, a turbulent expanse of cloud gas from the vicinity of a stellar source Part of the SF process mass-loss phase during their protostellar stages 1 1 Arce et al Search for outflows associated with methanol masers – the latter always associated with high mass SF its dynamic lifetime = upper bound on maser lifetime De 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.
Heterodyne Array Receiver Program 16 pix heterodyne focal-plane array receiver 4x4 element array with SIS detectors Beam size 345 GHz High 3D mapping speed sensitivity at GHz
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. 13 CO J=3-2 (trace outflows) C 18 O J=3-2 (see core) Masers selected with wide range of luminosities, distances and galactic longitudes analyse differences in outflow properties.
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
~ 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 # Time Example: 13 CO images from Maser source G RA Dec CUBECOLLAPSED CUBE More edge clipping Despike Rebin velocity Switch of noisy receptors
Aim of this phase: Simple outflow detection & contour mapping 3D image rendering with current astronomical software (GAIA) of both 13 CO and C 18 O. Detect outflows in 3D by eye Create a 3D training set for future medical image analysis programs
Simple outflow detection method 1 : Using median filter: determine central v and width of source peak Derive from above: define BLUE = (-10 ; -2 ) GREEN = (-2 ; 2 ) RED = (2 ; 10 ) 1. Private communication: Antonio Chrysostomou – JAC, Hawaii
Simple outflow detection method 1 : Using median filter: determine central v and width of source peak Derive 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: 13 CO image from Maser source G
3D rendering in Gaia 3 separation between contours (receptor temp). Levels: 6.6 K; 4.3 K, 2.1 K Blue: 13 CO; Yellow: C 18 O; Plane: image plane located at central peak velocity C 18 O : abundance thus opacity see core 13 CO > abundant than C 18 O, see more structure like outflows. Both molecules low enough density & low opacity – trace dense gas in molecular cores where masers are embedded.
Another example of high velocity structures (possible outflows?) Contours and 3D rendering of 13 CO and C 18 O images of G However, still inconclusive, need to be confirmed. 3 separation between contours (receptor temp). Levels: 6.1 K; 3.8 K, 1.5 K
Expand data Expand current data set of 80 sources with 13 CO and C 18 O maser observations from T. Moore Get 12 CO images for all maser sources from 12 CO galactic plane survey (JAC)
Investigate Medical Imaging options Outflows = irregular 3D shapes similarities with typical medical imaging problems Arce 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 Borkin et al. 2005
“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