5 antennas in 300-km range ALMA ALMA Extended Array 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 Thermal Universe with a VLBI resolution

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 2 Discussion in the Next-Generation sub-mm WG ALMA enhanced array earth-like planets large scale structure / DM mapping SZ kinematics BH imaging stellar imaging / astrometry Possible in only radio / needed from non-radio 井口 (2009) : 宇電懇シンポジウム 80 ant’s / 128 GHz BW / 300 km baseline working on 2009 Mar - Nov 5 antennas sensitivity : sec resolution 0.6 mas Tb sensitivity 1000 K ALMA extended array is mid-term program directing the ALMA enhanced array …proposed to the science council of Japan, as a mid-term program

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 3 Positioning ALMA extended array 5 antennas sensitivity : sec resolution 0.6 mas Tb sensitivity 1000 K ALMA extended array is mid-term program directing the ALMA enhanced array …proposed to the science council of Japan, as a mid-term program Thermal Universe with a VLBI resolution

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 4 ALMA extended configuration 5 antennas in 300-km range ALMASitesAltitudeLatitudeLongitude Distance from ALMA km km km km km Tentative site locations … to be surveyed further higher altitude, needed for > 350 GHz

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

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 6 Science highlights : Black Holes Sub-mm galaxies discovered with ASTE (Tamura+09 Nature, 459, 61) Supermassive Black Holes (SMBHs) in galaxies 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 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 ） Evolving BH in a galaxy (artist’s impression) SED of SgrA* RIAF disk (Yuan+03 ApJ, 598, 301)

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 Probing mass accretion to AGN 福江純「輝くブラックホール 降着円盤」 p.162 What is the source: Stars, Gas, or Dust? How does matter lose angular momentum? Spatial resolution imaged by AeA Galactic rotation ↓ BH-bound rotation in 1-10 pc Cen A w/ SMA : Espada+09, ApJ, 695, 116

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 8 Approaching the central engine of AGNs Black-hole positioning by multifrequency core-position offset (Hada+11, Nature, 477, 185) 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 Simulation images : Nagakura & Takahashi (2010)

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 9 Space VLBI route to BH imaging Longer Baseline Realm of Space VLBI Space VLBI route

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 10 ALMA extended route to BH imaging Realm of Space VLBI ALMA extended route

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

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 12 Science highlights : Stars Stellar physics 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 Betelgeuse NIR image (10-mas resolution) (Kervella+09, A&A, 504, 115) 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 NIR visibilities

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 13 ALMA stellar imaging Size measurements (photosphere imaging) of nearby Giants Stellar apparent diameter Flux density e.g K, 300 R 1 kpc → 1.7 mJy → 7σ detection requires 10-min. w/ ALMA (cycle 1) Antares (700 R , 175 pc) → 40 mas Antares ( GHz → 290 mJy Goals: Tests for stellar size measurements Tests for distance estimation Critical point: Higher resolution (< 1 mas) is needed (47 sec on-source)

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 14 Stellar imaging with extended ALMA ・ Main sequence stars in 100 pc ・ Giants in 10 kpc Imaging / Apparent size of ← 6μJy sec w/ full-spec ALMA (+16 GHz BW) Direct distance measurements without parallax if linear size is known - Galactic plane, invisible by GAIA - Num. of stars overwhelming VERA

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 15 Science goals of stellar size / imaging Science goals : phase 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 Science goals : phase 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 500 supergiants for phase 1

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 ALMA capability + VLBI tech. →high res/sensitivity RequirementsSchedule Costs FYXX+1X+2X+3X+4X+5X+6… survey const- ruction opera- tion Site survey Technical development Infrastructure Antenna RX / Backends Tests Full Op. 12 m (ALMA design) x 5 antennas 12 m (ALMA design) x 5 antennas BW 16 GHz (4 GHz x 2SB x Dual pol.) BW 16 GHz (4 GHz x 2SB x Dual pol.) Baseline 300 km Baseline 300 km Frequency 350 GHz (230 GHz, 650 GHz) Resolution 0.6 mas Image sensitivity 7σ = 10 μJy (1 hr) Tb sensitivity 7σ = 1000 K (1 hr) Site candidates (need survey) Specs. Stations ￥ 1970 M/ant×5 = ￥ 9850 M site 150 M, ant 1400 M, FE 300 M, BE 120 M Computing ￥ 200 M Tests ￥ 600 M Management s ￥ 200 M total ￥ B (~ $140 M)

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 17 Possible cost-reduction plans Refurbish ASTE/NMA antenna surface panel replacement accuracy for 350 GHz drive system, pointing accuracy 10-m diameter (-30% aperture area) 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) Antennas : majority of costs VLBI recording (HDD/SSD) trade off between fibre link expected operation ~ 1000 hr/yr (phase I) 8 GB/s x 3.6e6 s x 6 station / 4 turn = 43.2 petabytes storage HDD cost ~ JPY 10 8 baseline SEFD : 1.2x

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 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

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 19 Summary / Open questions Does this array offer rich science? ‣ Science WG to be organized Is the array affordable? International collaborations, definitely needed Can technical issues feasible? Thermal Universe with a VLBI resolution

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 20 (u, v) coverage for -30º

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 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 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 計画として未熟 … 十分に時間をかけて検討すべき 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

国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ /21 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 : / を準備中