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The Galactic Australia SKA Pathfinder Spectral Line Survey (GASKAP)

The Galactic Australia SKA Pathfinder Spectral Line Survey (GASKAP). Milky Way Galaxy Workshop in Kagoshima University on 2012 September 6. Hiroshi Imai Graduate School of Science and Engineering, Kagoshima University

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The Galactic Australia SKA Pathfinder Spectral Line Survey (GASKAP)

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  1. The Galactic Australia SKA Pathfinder Spectral Line Survey (GASKAP) Milky Way Galaxy Workshop in Kagoshima University on 2012 September 6 Hiroshi Imai Graduate School of Science and Engineering, Kagoshima University International Centre for Radio Astronomy Research, The University of Western Australia

  2. Contents • From to VERA to SKA • astrometry of OH and CH3OH maser sources • ASKAP: Phased Feed Array (PFA), operation from 2013 • Concepts of the GASKAP survey • HI and thermal OH emission mapping • HI and OH absorption, OH maser source survey • From the Galactic plane to the Magellanic System • Design Stay Phase of GASKAP • Wide-field imaging • Automatic source finding Supported by the Strategic Young Researcher Overseas Visits Program for Accelerating Brain Circulation funded by Japan Society for the Promotion of Science

  3. Square Kilometer Array • South Africa + Australia • Aperture=50 VLA • Core + remote stations • λ= 3 - 30 cm • θSKA~θVLA/80 (15 mas @18cm) • Operation from ~2020 • Main scientific goals: • Life in the universe • Dark age of the universe • Evolution of the cosmic magnetic field • Probing gravity, dark matter • Evolution of galaxies Astrometric approaches based on experiences with VLBI/VERA

  4. Radio astrometry in era of SKA • Present • VLBA/HSA/VERA/EVN/LBA • Baseline SEFD=200 Jy (VLBA-GBT) • σ~10 microarcsecond • ~700 H2O masers • ~200 CH3OH masers • ~300 pulsars • ~500 nonthermal sources • Galactic thin disk • Solar neighborhood (<2 kpc) • SKA era • Baseline SEFD=2.4 Jy (core-remote) • σ~10 microarcsecond • ~5000 OH masers (1612/1665/1667/1720MHz) • ~5000 (6.7 GHz) CH3OH masers • ~5000 pulsars • >1000 nonthermal sources • Galactic thick disk • Galactic center, bulge, halo • Magellanic System • Wide FoV, space VLBI?

  5. ASKAPAustralia SKA Pathfinder • 36 12-m dish antennas • θ~30”@1.6GHz • Radio Quiet Zone in western Australia • 0.7—1.8 GHz • Focal Plane Phased-Array (FPA): 188 beams, 30 deg2 FoV • 8 times as fast sky survey as VLA • 300 MHz bandwidth (good for HI and OH) • 16384 spectral channels • Yielding closure phase in 2012 Aug. • Commissioning from 2013 • Scientific operation from 2014 • Dedicated for large surveys

  6. GASKAPGalactic ASKAP Spectral Line Survey • One of the Survey Science Programs (SSPs) defined in ASKAP. • A program integrated since the Expression of Interests in 2009. • The fastest sky surveys toward the Galactic plane, Magellanic Clouds, Stream, and Bridge. • Simultaneous mapping of HI (1.4 GHz)and OH (1.6 GHz). • ~7,000 hours in total, 0.15—2.40 hr/deg2 • Exploration of HI gas circulation between the disk and low latitude halo/MCs. • Galactic dynamics probed by OH maser sources • star forming regions (1665/1667 MHz) • circumstellar envelopes (16120 MHz) GASKAP logo designed by Josh Peek

  7. GASKAP international team • Principal Investigator • John Dickey (Univ. Tasmania) • Naomi McClure-Griffiths (ATNF, Australia) • Steering committee • Steven Gibson(Western Kentucky Univ. USA) • José F. Gómez (CSIC, Spain) • Hiroshi Imai (Kagoshima Univ. Japan) • Paul Jones (Univ. New South Wales, Australia) • Snězana Stanimirović (Univ. Wisconsin) • Jacco van Loon (Keele Univ. United Kingdom) • ~80 team members, now growing • First publication • Dickey J.M. et al. 2012, PASA (arXiv;1207.0891) • Now working in “Design Study Phase”.

  8. Survey area • Galactic plane (|b|<10°, δ<40°) • Magellanic System (LMC, SMC, Bridge, Stream)

  9. Approved possible

  10. Dynamic HI motions and filamentary strucutres on 0.1—100 pc scale 1 kpc @D=21 kpc • Magellanic leading arm high-velocity cloud interacting with the Galactic plane (McClure-Griffiths et al. 2008) • Opaque HI filaments on 15 pc scale in LMC, well correlated with CO clumps (Brown et al. 2012, IAUS 290)

  11. Bubbles, arcs, and loopsin the whole Milky Way Magellanic leading arm high-velocity cloud interacting with the Galactic plane (McClure-Griffiths et al. 2008) Any gas structure traced by HI emission Circulation of material between stars and interstellar space “2° UV tail” of Mira (Martin et al. 2007) “CO gas loops” (Fukui et al. 2006)

  12. Stellar OH maser sources distributed in the whole Milky Way Mira variables, OH/IR stars post-AGB stars, supergiants, From targeted (VLA/Parkes/ATCA) to unbiased sky survey (GASKAP) http://www.hs.uni-hamburg.de/~st2b102/maserdb

  13. Stellar 1612 MHz OH masers • Clear double peaks in circumstellar envelopes trigonometric parallax /geometric distance measurable. • Typical (O-rich) OH/IR stars in MW. • Red supergiants in LMC and SMC. Spectrum (Diamond et al. 1985) http://www.hs.uni-hamburg.de/ ~st2b102/maserdb Light curve (Herman & Habing 1985)

  14. Predicted 1612 MHz OH maser detection • Detecting typical (O-rich) OH/IR stars in MW. • Red supergiants in LMC and SMC. • Slower expansion velocity envelope in LMC/SMC due to lower metallicity? • SKA astrometry: LMC/SMC rotation and secular motions J. van Loon (see GASKAP proposal)

  15. More realistic OH maser catalog for GASKAP • Based on existing 1612 MHz OH maser catalogs • A complete blind survey with VLA towards the Galactic Center (Sjouwerman et al. 1998) • Incomplete catalog towards the whole Galaxy (Engels 2007) … GASKAP can double OH maser sources. • Candidates for OH maser sources • MSX sources (~80% coincidence within 20”) • SiO maser sources (~20% coincidence within 20”) Simulated OH maser histogram within 3 deg from GC (J.F. Gomeź) Log (Flux density [mJy])

  16. GASKAP Working Groups in Design Study Phase • WG1: Simulation • Calibration and imaging (de-convolution for diffuse source) • Multiple gridding (30”, 60”, 90”, 180”) • Simulated source catalogs of OH masers • WG2: Source finding from image cubes • CLUMPFIND, DUCHAMP, etc. in a huge image cube • WG3: Survey strategy • WG4: ASKAP hardware commitment • Correlation in zoom mode, band-pass stability • WG5: Data management • Output data format for a virtual observat0ry Progress should be reported to /evaluated by (annually) the ASKAP Internal Review Committee.

  17. Simulations of automatic source finding • Software: Duchamp / Selavy (for ASKAP) • Smoothing and flagging of image cubes • Image cube statistics (MADFM) • Source identification without interpretation (fitting) • Source growing, catalog output • Simulation environments • Local CPUs + theSkyNet (~2000 CPUs) • My Mac for result analysis • Goals • To find out the major parameters that dominate source finding results. • To find the best sets of input parameters to yield the best combination of completeness and reliability. http://www.theskynet.org

  18. Simulation procedures (HI’s simulation in ICRAR) • Input source distribution (by José F. Gómez) 1338 OH maser features towards the Galactic center • Simulated image cubes (by Tobias Westmeier) 1538 x 1538 x 4000 pixels, 10” and 0.1 km/s grid Dirty (undeconvolved) and CLEANed (deconvolved) cubes • Prepare sets of Duchamp input parameters (python scripts, by HI) ~10 / ~2000 sets of parameters for local CPUs / theSkyNet • Compare the output identification with the input source catalogs to judge true / false detections • Calculate identification completeness and reliability • Make statistical analysis with many sets of completeness and reliability • Analyze which kind of identifications become true/false (in case-by-case)

  19. Unidentified sources in the mode sources In CLEANed image cube . True detection ・ false detection

  20. Completeness and reliabilityagainst source peak intensity(example)

  21. Current status of source finding simulations • Analyzer scripts almost completed. • With CLEANed image cube • Reasonable results with minor unexpected performance • With dirty (conservative) image cube • Miserable results • Difficulty in major parameters to cause the results • theSkyNet simulation (4 weeks in total) • 1st round on June 15-20: too long, too miserable! • 2nd round in end of September

  22. Summary • Optimistic future of radio astrometry for vast of exotic sources (pulsars and masers in the local universe) • High sensitivity, wide field of view, (+space VLBI?) • Preparatory works towards radio astrometry / maser source survey in SKA/ASKAP era • Milestones in automatic data processing/ analysis • theSkyNet ~ SETI@home based scheme for vast public computation • VLBI demonstration in low-frequency astrometry • EVN / LBA / VLBA EAVN? • Multi-reference source astrometry

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