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5 antennas in 300-km range

ALMA. 5 antennas in 300-km range. ALMA Extended Array. Thermal Universe with a VLBI resolution. Seiji Kameno (Kagoshima Univ.) Naomasa Nakai (Tsukuba Univ.) Mareki Honma (NAOJ). Overview Science case BH in galaxies Stellar imaging / size Schedule and costs Technical issues.

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5 antennas in 300-km range

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  1. ALMA 5 antennas in 300-km range ALMA Extended Array Thermal Universe with a VLBI resolution Seiji Kameno (Kagoshima Univ.) Naomasa Nakai (Tsukuba Univ.) Mareki Honma (NAOJ) • Overview • Science case • BH in galaxies • Stellar imaging / size • Schedule and costs • Technical issues

  2. ALMA extended array is mid-term program directing the ALMA enhanced array • earth-like planets • large scale structure / DM mapping • SZ kinematics • BH imaging • stellar imaging / astrometry • 5 antennas • sensitivity : 10μJy@3600 sec • resolution 0.6 mas • Tb sensitivity 1000 K …proposed to the science council of Japan, as a mid-term program Discussion in the Next-Generation sub-mm WG working on 2009 Mar - Nov Possible in only radio / needed from non-radio ALMA enhanced array 80 ant’s / 128 GHz BW / 300 km baseline 井口 (2009) : 宇電懇シンポジウム

  3. ALMA extended array is mid-term program directing the ALMA enhanced array • 5 antennas • sensitivity : 10μJy@3600 sec • resolution 0.6 mas • Tb sensitivity 1000 K …proposed to the science council of Japan, as a mid-term program Positioning ALMA extended array Thermal Universe with a VLBI resolution

  4. ALMA extended configuration Tentative site locations … to be surveyed further ALMA 5 antennas in 300-km range higher altitude, needed for > 350 GHz

  5. Thermal Universe with a VLBI resolution Science Case 1 Black holes in galaxies

  6. Science highlights : Black Holes Supermassive Black Holes (SMBHs) in galaxies Sub-mm galaxies discovered with ASTE (Tamura+09 Nature, 459, 61) • Sub-mm galaxies in the early Universe • Search for SMBHs in high-z galaxies • Clarify Galaxy / SMBH co-evolution • High resolution to discriminate AGN from SB Evolving BH in a galaxy (artist’s impression) SED of SgrA* RIAF disk (Yuan+03 ApJ, 598, 301) • BH engines in nearby AGNs • Mass accretion process from galactic disk to BH • Census for RIAF at sub-mm SED peak • Imaging BH+accretion disk（as a part of sub-mm VLBI）

  7. Probing mass accretion to AGN How does matter lose angular momentum? What is the source: Stars, Gas, or Dust? Galactic rotation ↓ BH-bound rotation in 1-10 pc Cen A w/ SMA : Espada+09, ApJ, 695, 116 Spatial resolution imaged by AeA 福江純「輝くブラックホール 降着円盤」p.162

  8. Approaching the central engine of AGNs Radio ‘photosphere’ of the jet …frequency dependent • Hi-Fi imaging at > 40 GHz • High frequency to see through jets • High dynamic range to discriminate the disk from jets • Middle baseline (~ a few 100 km) to fill (u, v) hole in sub-mm VLBI Black-hole positioning by multifrequency core-position offset (Hada+11, Nature, 477, 185) Simulation images : Nagakura & Takahashi (2010)

  9. Space VLBI route to BH imaging Realm of Space VLBI Longer Baseline Space VLBI route

  10. ALMA extended route to BH imaging Realm of Space VLBI ALMA extended route

  11. Thermal Universe with a VLBI resolution Science Case 2 Stellar imaging / size measurements

  12. Science highlights : Stars Stellar physics Betelgeuse NIR image (10-mas resolution) (Kervella+09, A&A, 504, 115) NIR visibilities • Imaging photospheres of nearby giants / supergiants • 100 x 100 pixel images for Betelgeuse and Antares (RSGs) • 4 x 4 pixel image for α Cen (MS) • Ellipticity (e.g. Achernar) • Flares, Prominences, CME • Convection cells / Dynamo • Motion of active regions • Magnetic inversion The sun imaged with the Nobeyama Radio Heliograph (180 x 180 pixel) Betelgeuse H-band image (9-mas resolution) (Haubois+09, A&A, 508, 923) comparison with the sun

  13. ALMA stellar imaging Size measurements (photosphere imaging) of nearby Giants • Stellar apparent diameter • Flux density Antares (700 R8, 175 pc) → 40 mas Antares (3000 K) @ 350 GHz → 290 mJy e.g. 3000 K, 300 R8@ 1 kpc → 1.7 mJy → 7σ detection requires 10-min. w/ ALMA (cycle 1) (47 sec on-source) • Goals: • Tests for stellar size measurements • Tests for distance estimation • Critical point: • Higher resolution (< 1 mas) is needed

  14. Stellar imaging with extended ALMA ・Main sequence stars in 100 pc ・Giants in 10 kpc Imaging / Apparent size of Direct distance measurements without parallax if linear size is known - Galactic plane, invisible by GAIA - Num. of stars overwhelming VERA ← 6μJy 3σ@3600 sec w/ full-spec ALMA (+16 GHz BW)

  15. Science goals of stellar size / imaging • Science goals : phase 1 • 500 supergiants to be imaged (δ < 20º, K < 6 mag, lumi. class I and II) • 1-hour / source → 500 hours • Verify previously measured size and distance • Establish size-spectral type-luminosity relation • Surface activity (flares, spots, convection cells) • Binary systems 500 supergiants for phase 1 • Science goals : phase 2 • 20000 giants (δ < 20º, lumi. class III) • 4 sources / hour → 5000 hours • Angular diameter → distance • Precise galactic structure and dynamics beyond the center (NA w/ GAIA) • Whole lifecycle of stars • BH mass accretion by stellar dynamics

  16. Requirements RX / Backends Specs. Site survey Antenna Tests Infrastructure Technical development Full Op. ALMA capability + VLBI tech. →high res/sensitivity Site candidates (need survey) • 12 m (ALMA design) x 5 antennas • BW 16 GHz (4 GHz x 2SB x Dual pol.) • Baseline 300 km Schedule Costs total ￥10.85 B (~ $140 M)

  17. Possible cost-reduction plans Antennas : majority of costs Refurbish ASTE/NMA antenna • surface panel replacement • accuracy for 350 GHz • drive system, pointing accuracy • 10-m diameter (-30% aperture area) baseline SEFD : 1.2x Some antennas from ALMA main array • ~ 5 years after ALMA’s full operation • User’s requests for high resolution, expected Credit: ALMA(ESO/NAOJ/NRAO) VLBI recording (HDD/SSD) storage 8 GB/s x 3.6e6 s x 6 station / 4 turn = 43.2 petabytes • trade off between fibre link • expected operation ~ 1000 hr/yr (phase I) HDD cost ~ JPY 108

  18. Technical Issues • Site survey • Higher altitude / sufficient (u, v) coverage • Sub-mm coherence at long baselines • LO distribution / individual frequency standards? • Phase compensation : switching / VERA-like dual beam? • Fiber connection • > 100 km optical fibre / VLBI recording? • Correlator • Number of baselines, faster phase tracking, larger delay buffer • Calibration plan • Are there good calibrators? • Operation planning • Impacts on ALMA • Multi-Frequency Synthesis

  19. Summary / Open questions Thermal Universe with a VLBI resolution • Does this array offer rich science? • Science WG to be organized • Is the array affordable? • International collaborations, definitely needed • Can technical issues feasible?

  20. (u, v) coverage for -30º

  21. 緊急性 「ALMAの初期成果を得てから進めてもよいのでは」 宇電懇ヒアリング時コメント Yes 計画として未熟 … 十分に時間をかけて検討すべき • サイエンス検討 • システム検討（サイト選定, アンテナ, 干渉技術, 記録系, 運用） • 国際協力 • 運用体制 運用開始目標 ~ 2019 (5 yrs since full ALMA) • ALMA利用の競争率低下の期待 • 高空間分解能への要求増 → ALMA Development Planへの申請

  22. 体制 : TBD 現状 関心を持つ研究者に声をかけている段階 ALMA extended array science workshop : 2012 11/15 -16を準備中

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