Workshop on EastAsian Collaboration for SKA in Daejeon

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

Contents l SKA and Australian SKA Pathfinder (ASKAP) l l 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 l Galactic ASKAP Spectral Line Survey (GASKAP) l l Survey specification: HI—OH mapping and OH maser survey Activities in the Survey Study Phase l Toward SKA astrometry l l Possible future collaboration in the Pacific region Current progress in VERA+KVN/ EAVN

High sensitivity astrometry with SKA (mid-band) l Aperture (dish)=50 VLAs l l l Baseline SEFD=2. 4 Jy (with core-remote station), enabling to use fainter phase-reference sources Image dynamic range=106 High angular resolution l l θSKA~θVLA/80 (3000 km), 2. 4 mas @ 3 cm Baseline extension with distant remote stations

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 GHz Δθ(target – reference) < 6 deg @6 GHz ~30, 000 reference sources with S 8 GHz > 1 m. Jy 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 Fo. V=30 deg 2 @1. 5 GHz

Wide band astrometry with SKA (mid band) l l l λ= 3 – 60 cm (0. 5 -10 GHz) Pulsar astrometry (main target? Tingay’s and Kameya’s talks) Thermal source astrometry (OB stars, YSOs) l l Recombination line and thermal continuum sources Proper motion measurement Non-thermal sources: annual parallaxes Maser source astrometry (in MHz) l l l OH: 1612, 1665, 1667, 1720, 4751, 4766, 6031, 6035, 13441 CH 3 OH: 6669, 12179 H 2 O: 22235, NH 3: 23694, 23723, 23870 (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)

Why OH maser astrometry? Major maser lines in SKA mid-band l Targets of wide-field VLBI astrometry l Nearby HI 21 -cm line l Wide variety of populations of OH maser sources l l 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 l l Light curve phase-lag technique for distance determination sites of present mass release from dying stars in the Milky Way

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 (ASKAP) http: //www. hs. uni-hamburg. de/~st 2 b 102/maserdb

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

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

Light curve phase-lag technique for distance determination W 43 A OH masers (Imai et al. 2002) van Langevelde et al. (1990) Herman & Habing (1985)

ASKAP Australian Square Kilometer Array Pathfinder (Norris’s talk) l l l 36 12 -m dish antennas Radio Quiet Zone in western Australia Focal Plane Phased-Array Antenna (FPA) covering 30 deg 2 300 MHz band width, 16384 spectral channels Operation from 2013

GASKAP: Galactic ASKAP Spectral Line Survey l l l l 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/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 l star forming regions (1665/1667 MHz) l circumstellar envelopes (16120 MHz) GASKAP logo designed by Josh Peek

GASKAP international team l P. I. John Dickey (Univ. Tasmania) l Steering committee l l l l Steven Gibson (Western Kentucky Univ. USA) José F. Gómez (CSIC, Spain) Hiroshi Imai (Kagoshima Univ. , Japan) Paul Jones (Univ. New South Wales, Australia) Naomi Mc. Clure-Griffiths (ATNF, Australia) Snězana Stanimirović (Univ. Wisconsin) Jacco van Loon (Keele Univ. , United Kingdom) l ~80 team members l Now working in “Design Study Phase”.

GASKAP Working Groups in Design Study Phase l WG 1: Simulations l l WG 2: Source finding from image cubes l l Management of field rotation in Phased Array Feed WG 4: ASKAP hardware commitment l l CLUMPFIND, DUCHAMP, Selavy, etc. for a huge image cube WG 3: Survey strategy l l Calibration and imaging (de-convolution for diffuse source) Multiple gridding (30”, 60”, 90”, 180”) Simulated source catalogs of OH masers Correlation in zoom mode, band-pass stability WG 5: Data management l Output data format for a virtual observat 0 ry

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

Approved possible

What we want to see in HI? 1 kpc @D=21 kpc Magellanic leading arm high-velocity cloud interacting with the Galactic plane (Mc. Clure-Griffiths et al. 2008) Dynamic atomic hydrogen motions on 0. 1— 1000 pc scale Comparison of HI sky surveys (Mc. Clure-Griffiths et al. 2009)

Bubbles, arcs, and loops in the whole Milky Way Any gas structure traced by HI emission “ 2° UV tail” of Mira (Martin et al. 2007) “CO gas loops” (Fukui et al. 2006) Magellanic leading arm high-velocity cloud interacting with the Galactic plane (Mc. Clure-Griffiths et al. 2008)

Predicted 1612 MHz OH maser detection Detecting typical (O -rich) OH/IR stars in MW. l Red supergiants in LMC and SMC. l Slower expansion velocity envelope in LMC/SMC due to lower metalicity? l J. van Loon (from GASKAP proposal)

More realistic OH maser catalog for GASKAP source finding simulation l Based on existing 1612 MHz OH maser catalogs l l l 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 l MSX (MIR) sources Simulated OH maser histogram within 3 deg from GC (J. F. Gómez) (~80% coincidence within 20”) l Si. O maser sources (~20% coincidence within 20”) Log (Flux density [m. Jy])

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

Technical challenging in GASKAP l Visibility calibration schemes in wide-field imaging. l l l 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”. l Emission identification in the complicated structures. l l l Including absorption Outputs in the “virtual observatory”. l l HI Image cubes …. huge file size! Fitting parameters for OH maser sources.

Current collaborations in East-Asian VLBI Network related to SKA l 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) l Planning KVN+VERA Key Science since 2011 June l (star formation, AGN, evolved stars, astrometry sub-WGs) l International team collaboration for development of multi-frequency band, phase-referencing technique (lead by U. Western Australia /ICRAR)

Possible GASKAP/SKA/EAVN collaboration in maser source astrometry