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![Page 1: The Galactic Australia SKA Pathfinder Spectral Line Survey (GASKAP) Hiroshi Imai Graduate School of Science and Engineering, Kagoshima University International.](https://reader036.fdocuments.net/reader036/viewer/2022062518/56649e555503460f94b4d158/html5/thumbnails/1.jpg)
The Galactic Australia SKA Pathfinder The Galactic Australia SKA Pathfinder Spectral Line Survey (GASKAP)Spectral Line Survey (GASKAP)
Hiroshi ImaiGraduate School of Science and Engineering, Kagoshima
UniversityInternational Centre for Radio Astronomy Research, The University
of Western Australia
Milky Way Galaxy Workshop
in Kagoshima Universityon 2012 September 6
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ContentsContentsFrom to VERA to SKA
astrometry of OH and CH3OH maser sources ASKAP: Phased
Feed Array (PFA), operation from 2013Concepts 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
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Square Kilometer ArraySquare Kilometer Array South Africa + Australia Aperture=50 VLA Core + remote stationsλ= 3 - 30 cmθSKA~θVLA/80 (15 mas @18cm) Operation from ~2020 Main scientific goals:1. Life in the universe2. Dark age of the universe3. Evolution of the cosmic magnetic field4.Probing gravity, dark matter5.Evolution of galaxies
Astrometric approaches based on experiences with VLBI/VERA
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Radio astrometry in era of SKARadio astrometry in era of SKA 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?
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)
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ASKAPASKAPAustralia SKA PathfinderAustralia SKA Pathfinder
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
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
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GASKAPGASKAPGalactic ASKAP Spectral Line SurveyGalactic 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
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GASKAP international teamGASKAP 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”.
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Survey areaSurvey area Galactic plane (|b|<10°, δ<40°) Magellanic System (LMC, SMC, Bridge, Stream)
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Approved Approved
possible possible
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Dynamic HI motions and filamentary strucutres Dynamic HI motions and filamentary strucutres on 0.1—100 pc scaleon 0.1—100 pc scale
• 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)
1 kpc @D=21 kpc
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Bubbles, arcs, and loopsBubbles, arcs, and loopsin the whole Milky Wayin the whole Milky Way
“2° UV tail” of Mira (Martin et al. 2007)
Magellanic leading arm high-velocity cloud interacting with the Galactic plane (McClure-Griffiths et al. 2008)
“CO gas loops” (Fukui et al. 2006)
Any gas structure traced by HI emissionCirculation of material between stars and interstellar space
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StellarStellar OH maser sources distributed OH maser sources distributed in the whole Milky Way in the whole Milky Way
Mira variables, OH/IR starspost-AGB stars, supergiants,
http://www.hs.uni-hamburg.de/~st2b102/maserdb
From targeted (VLA/Parkes/ATCA) to unbiased sky survey (GASKAP)
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Stellar 1612 MHz OH masersStellar 1612 MHz OH masers
Clear double peaks in circumstellar envelopestrigonometric 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)
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Predicted 1612 MHz OH maser detectionPredicted 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)
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More realistic OH maser catalog for GASKAPMore realistic OH maser catalog for GASKAPBased 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])
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GASKAP Working Groups in Design Study PhaseGASKAP 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.
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Simulations of automatic source findingSimulations 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
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Simulation procedures (HI’s simulation in ICRAR)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)
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Unidentified sources in the mode sourcesUnidentified sources in the mode sources
In CLEANedimage cube
. True detection・ false detection
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Completeness Completeness and reliabilityand reliabilityagainst source against source peak intensitypeak intensity
(example)(example)
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Current status of source finding simulationsCurrent 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
resultstheSkyNet simulation (4 weeks in total)
1st round on June 15-20: too long, too miserable!
2nd round in end of September
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SummarySummary 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