Astrometry with SKA: case of OH maser sources Hiroshi Imai Graduate School of Science and Engineering, Kagoshima University GASKAP collaboration Workshop on East-Asian Collaboration for SKA in Daejeon, Korea on 2011 December 2

SKA 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 Phase Toward 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=10 6 High angular resolution θ SKA ~θ VLA /80 (3000 km), 2.4 3cm Baseline extension with distant remote stations

Permitted phase coherence angle within atmospheric fluctuation for 10-μas level astrometry (e.g. Asaki et al. 2007) Δθ (target – reference) < 2 GHz Δθ (target – reference) < 6 GHz ~30,000 reference sources with S 8GHz > 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 deg

λ= 3 – 60 cm ( 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, CH 3 OH: 6669, H 2 O: 22235, NH 3 : 23694, 23723, (high-band) OH maser survey in GASKAP and OH maser astrometry (this talk) Galactic kinematics of CH 3 OH maser sources (Matsumoto’s talk) Internal motions and kinematics H 2 O masers (Chibueze’s talk)

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

Mira variables, OH/IR stars post-AGB stars, supergiants, From targeted (VLA/Parkes/ATCA) to unbiased sky survey (ASKAP)

Tracing Galactic rotation and arms (|b|<1 deg) Credit: Daniel Tafoya

Using tangential point method in each longitude bin R 0 =8kpc θ 0 = 200 km/s Credit: Daniel Tafoya Stellar OH maser sources = collision-less system transparent toward Galactic plane

van Langevelde et al. (1990) Herman & Habing (1985) W43A OH masers (Imai et al. 2002)

ASKAP Australian Square Kilometer Array Pathfinder (Norris’s talk) m dish antennas Radio Quiet Zone in western Australia Focal Plane Phased-Array Antenna (FPA) covering 30 deg MHz band width, spectral channels Operation from 2013

GASKAP: Galactic ASKAP Spectral Line Survey One of the Survey Science Programs (SSPs) defined in ASKAP. A program integrated since the Expression of Interests in 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/deg 2 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 team P.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 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 areas Galactic plane (|b|<10°, δ<40°) Magellanic Clouds, Stream, Bridge Galactic bulge, center and lower halo (GASKAP+ ?)

Approved possible

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 Dynamic atomic hydrogen motions on 0.1—1000 pc scale

“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 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 GASKAP 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 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

Input single channel map 90” resolution synthesized image CLUMPFIND identification clump distribution Next goal: removing artifacts through finding multi-channel correlation (will be tested with VERA data) Credit: J.F. Gomez

Technical 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.

SKA-JP sub-WG on Astrometry Y. 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 CH 3 OH 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)