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

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

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

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)

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

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

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”.

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

Approved Approved

possible possible

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

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

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)

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)

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)

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])

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.

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

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)

Unidentified sources in the mode sourcesUnidentified sources in the mode sources

In CLEANedimage cube

. True detection・ false detection

Completeness Completeness and reliabilityand reliabilityagainst source against source peak intensitypeak intensity

(example)(example)

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

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