5 antennas in 300-km range

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


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



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

Science Case 1

Black holes in galaxies



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


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)


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

Science Case 2

Stellar imaging / size measurements



/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


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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)


/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


/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)


/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


/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


/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?



/21

(u, v) coverage for -30º(u, v) coverage for -30º


/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


/21

体制 : TBD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

5 antennas in 300-km range

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