Astrometry with SKA: case of OH maser sources

Hiroshi ImaiGraduate School of Science and

Engineering, Kagoshima UniversityGASKAP collaboration

Workshop on East-Asian Collaboration for

SKA in Daejeon, Korea on 2011

December 2

ContentsContentsSKA and Australian SKA Pathfinder (ASKAP)

High sensitivity, wide-band, wide-field astrometry Stellar and interstellar OH masers as a probe of

stellar mass loss flows and the Milky Way dynamics Galactic ASKAP Spectral Line Survey (GASKAP)

Survey specification: HI—OH mapping and OH maser survey

Activities in the Survey Study PhaseToward SKA astrometry

Possible future collaboration in the Pacific region Current progress in VERA+KVN/ EAVN

Aperture (dish)=50 VLAs Baseline SEFD=2.4 Jy (with core-remote station),

enabling to use fainter phase-reference sources

Image dynamic range=106 High angular resolution

θSKA~θVLA/80 (3000 km), 2.4 mas @ 3cm Baseline extension with distant remote stations

High sensitivity astrometry with SKA High sensitivity astrometry with SKA (mid-band)(mid-band)

Wide-field astrometry with SKA (mid-band)Wide-field astrometry with SKA (mid-band)Permitted phase coherence angle within atmospheric fluctuation for 10-μas level astrometry

(e.g. Asaki et al. 2007)Δθ(target – reference) < 2 deg @22 GHzΔθ(target – reference) < 6 deg @6 GHz

~30,000 reference sources with S8GHz > 1 mJy

Δθ(reference – reference) ~0.7 deg Multi-reference, in-beam astrometry is possible.Wide-angle astrometry is still necessary and possible for estimation/ correction of zenith delay residuals.

ASKAP focal plane phased array FoV=30 deg2 @1.5GHz

Wide band astrometry with SKA (mid band)Wide band astrometry with SKA (mid band)λ= 3 – 60 cm (0.5-10 GHz) Pulsar astrometry (main target? Tingay’s and

Kameya’s talks) Thermal source astrometry (OB stars, YSOs)

Recombination line and thermal continuum sources Proper motion measurement

Non-thermal sources: annual parallaxes Maser source astrometry (in MHz)

OH: 1612, 1665, 1667, 1720, 4751, 4766, 6031, 6035, 13441 CH3OH: 6669, 12179 H2O: 22235, NH3: 23694, 23723, 23870 (high-band) OH maser survey in GASKAP and OH maser astrometry (this talk) Galactic kinematics of CH3OH maser sources (Matsumoto’s talk) Internal motions and kinematics H2O masers (Chibueze’s talk)

Why OH maser astrometry?Why OH maser astrometry? Major maser lines in SKA mid-band Targets of wide-field VLBI astrometry Nearby HI 21-cm line Wide variety of populations of OH maser sources

star forming regions (high-mass, intermediate mass YSOs) in the Galactic thin disk

evolved stars (long period variables, OH/infrared stars) in Galactic thick disk, bulge, halo (including globular clusters)

Unique property of 1612 MHz OH maser sources Light curve phase-lag technique for distance

determination sites of present mass release from dying stars in the

Milky Way

Stellar OH maser sources distributedStellar 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 (ASKAP)

OH maser distributionOH maser distribution Tracing Galactic rotation and arms (|b|<1 deg)

Credit: Daniel Tafoya

Rotation curve derived with OH masersRotation curve derived with OH masers Using tangential point method in each longitude bin

R0=8kpcθ0= 200 km/s

Credit: Daniel Tafoya

Stellar OH maser sources= collision-less system transparent toward Galactic plane

Light curve phase-lag technique for distance determinationLight curve phase-lag technique for distance determination

van Langevelde et al. (1990) Herman & Habing (1985)

W43A OH masers(Imai et al. 2002)

ASKAPASKAPAustralian Australian

Square Kilometer ArraySquare Kilometer ArrayPathfinderPathfinder

(Norris’s talk)(Norris’s talk) 36 12-m dish antennas Radio Quiet Zone in western

Australia Focal Plane Phased-Array

Antenna (FPA) covering 30 deg2

300 MHz band width, 16384 spectral channels

Operation from 2013

GASKAP: GASKAP: Galactic 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 surveys of HI / OH thermal and OH maser

emission in the Milky Way, 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 Sites of present stellar mass loss in the Miky Way

star forming regions (1665/1667 MHz) circumstellar envelopes (16120 MHz)

GASKAP logo designed by Josh Peek

GASKAP international teamGASKAP international teamP.I. John Dickey (Univ. Tasmania)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) Naomi McClure-Griffiths (ATNF, Australia) Snězana Stanimirović (Univ. Wisconsin) Jacco van Loon (Keele Univ., United

Kingdom)~80 team members Now working in “Design Study Phase”.

GASKAP Working Groups in Design Study PhaseGASKAP Working Groups in Design Study Phase

WG1: Simulations 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, Selavy, etc. for a huge

image cube WG3: Survey strategy

Management of field rotation in Phased Array Feed WG4: ASKAP hardware commitment

Correlation in zoom mode, band-pass stability WG5: Data management

Output data format for a virtual observat0ry

Survey areasSurvey areas Galactic plane (|b|<10°, δ<40°) Magellanic Clouds, Stream, Bridge Galactic bulge, center and lower halo (GASKAP+ ?)

Approved Approved

possible possible

What we want to see in HI?What we want to see in HI?

Comparison of HI sky surveys (McClure-Griffiths et al. 2009)

Magellanic leading arm high-velocity cloud interacting with the Galactic plane (McClure-Griffiths et al. 2008)

1 kpc @D=21 kpc

Dynamic atomic hydrogen motions on 0.1—1000 pc scale

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)

Any gas structure traced by HI emission

“CO gas loops” (Fukui et al. 2006)

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 metalicity?

J. van Loon (from GASKAP proposal)

More realistic OH maser catalog for More realistic OH maser catalog for GASKAP source finding simulationGASKAP source finding simulation

Based on existing 1612 MHz OH maser catalogs A complete unbiased deepy 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 (MIR) sources

(~80% coincidence within 20”) SiO maser sources

(~20% coincidence within 20”)

Simulated OH maser histogram within 3 deg from GC (J.F. Gómez)

Log (Flux density [mJy])

Simulation of HI map reproductionSimulation of HI map reproduction Input: HI map from previous observations (right) Output: Map reproduction in ASKAP configuration (left)

Good recovery in 180” resolution

ASKAP+Parkes

Credit: P. Jones

From imaging to source From imaging to source identificationidentification

Input single channel map 90” resolution synthesized image

CLUMPFIND identification clump distribution

Next goal: removing artifactsthrough finding multi-channel correlation (will be tested with VERA data)

Credit: J.F. Gomez

Technical challenging in GASKAPTechnical challenging in GASKAP Visibility calibration schemes in wide-field imaging.

With/without using calibrators in the same scan field Uniform sensitivity in the whole scan field and frequency

band Real-time processing of calibration

Automatic and reliable visibility calibration through “the pipeline”.

Emission identification in the complicated structures. Including absorption

Outputs in the “virtual observatory”. HI Image cubes …. huge file size! Fitting parameters for OH maser sources.

Current collaborations in East-Asian VLBI NetworkCurrent collaborations in East-Asian VLBI Networkrelated to SKArelated to SKA

SKA-JP sub-WG on AstrometryY. Asaki (ISAS/JAXA), H. Imai, D. Tafoya (Kagoshima Univ.), K. Ohnishi

(Nagano Nat’l. College of Technology), T. Hirota, Y. Hagiwara, N. Matsumoto (NAOJ/Mizusawa VLBI), Niimura (Yamaguchi Univ.), N. Goda, T. Tsujimoto, T. Yano (NAOJ/JASMINE), Mitsumi Fujishita (Tokai Univ.)

VLBI demonstrations for 6.7 GHz CH3OH maser sources in JVN and SHAO since 2010 Autumn (See Matsumoto’s talk)

Planning KVN+VERA Key Science since 2011 June (star formation, AGN, evolved stars, astrometry sub-WGs)

International team collaboration for development of multi-frequency band, phase-referencing technique (lead by U. Western Australia /ICRAR)

Possible GASKAP/SKA/EAVN collaborationPossible GASKAP/SKA/EAVN collaborationin maser source astrometryin maser source astrometry