5 antennas 5 antennas inin
300-km 300-km rangerange
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 2 /21
Discussion in the Next-Generation sub-mm WGDiscussion 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 : 10μJy@3600 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 3 /21
Positioning ALMA extended arrayPositioning ALMA extended array
•5 antennas•sensitivity : 10μJy@3600 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 4 /21
ALMA extended configurationALMA extended configuration
5 antennas 5 antennas inin
300-km 300-km rangerange
ALMASitesSites AltitudeAltitude LatitudeLatitude LongitudeLongitude Distance Distance
from ALMAfrom ALMA
11 4100 -25.205 69.173 266 km
22 3200 -22.267 68.950 134 km
33 2900 -24.253 69.057 171 km
44 2400 -24.550 70.333 290 km
55 3600 -25.130 68.925 248 km
Tentative site locations… to be surveyed
further
higher altitude, needed for > 350 GHz
国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ 6 /21
Science highlights : Black HolesScience 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 AGNProbing 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 8 /21
Approaching the central engine of AGNsApproaching 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 9 /21
Space VLBI route to BH imagingSpace VLBI route to BH imaging
Longer
Baselin
e
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 10
/21
ALMA extended route to BH imagingALMA extended route to BH imaging
Realm of Space VLBI
ALM
A e
xte
nded ro
ute
国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ 12
/21
Science highlights : StarsScience 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 13
/21
ALMA stellar imagingALMA stellar imaging
Size measurements (photosphere imaging) of nearby Giants
• Stellar apparent diameter
• Flux density
e.g. 3000 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 (3000 K) @ 350 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 14
/21
Stellar imaging with extended ALMAStellar imaging with extended ALMA
・ Main sequence stars in 100 pc・ Giants in 10 kpc
Imaging / Apparent size of
← 6μJy3σ@3600 secw/ 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 15
/21
Science goals of stellar size / imagingScience 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
• 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
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/sensitivityALMA capability + VLBI tech. →high res/sensitivity
Requirements
ScheduleSchedule
CostsCostsFY X X+1 X+2 X+3 X+4 X+5 X+6…
survey
const-ruction
opera-tion
Site survey
Technical development
Infrastructure
Antenna
RX / Backends
Tests
Full Op.
•12 m (ALMA design) x 5 antennas12 m (ALMA design) x 5 antennas•BW 16 GHz (4 GHz x 2SB x Dual BW 16 GHz (4 GHz x 2SB x Dual pol.)pol.)•Baseline 300 kmBaseline 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 Msite 150 M, ant 1400 M, FE 300 M, BE 120 M
Computing ¥ 200 M
Tests ¥ 600 M
Managements
¥ 200 M
total ¥ 10.85 B (~ $140
M)
国立天文台電波専門委員会 2012/9/23 : ALMA 拡張アレイ 17
/21
Possible cost-reduction plansPossible 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 108
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 18
/21
Technical IssuesTechnical 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 19
/21
Summary / Open questionsSummary / 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
/21
緊急性緊急性
「 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