Scientific and technical feasibilities of VSOP-2 astrometry of H2O masers

in the Magellanic Clouds

Hiroshi Imai(Kagoshima University)

VSOP-2 KSP Maser Working Group

version on 2010 April 281

Key issues in scientific and technical feasibilities

(in lower ASTRO-G sensitivity case)

• Targets of H2O maser astrometry with VSOP-2: the Galactic System

Milky Way (D>10 kpc), LMC, SMC• scientific feasibility of study on H2O masers

– scientific background: c.f. astrometry with GAIA– scientific rationale: deviation from galactic rotations– challenging: trigonometric parallax measurements

• technical feasibility– phase-referencing (ASTRO-G orbits, calibration)– image quality v.s. maser spot / reference source structures– sensitivity: ~1 Jy (H2O maser), ~300 mJy (reference) – observation scheduling: depending on tracking stations 2

Scientific feasibility of VSOP-2 study on H2O masers

1. Maser astrometry– Current trigonometric distance scale < diameter of the Galaxy– Current proper motion measurements > 1-year baseline– Current main topics

• global parameters of the Milky Way• Individual local YSOs and evolved stars in the Milky Way

– Targets of VSOP-2• trigonometric distance scale over 10 kpc• proper motions of 100 μas yr-1 within 1 year baseline• YSOs and evolved stars in critical or rate phases and sites

critical evolutional phases: YSO mass accretion or helical jet formationcritical astrophysical sites: LMC and SMC, (mini) starburst in LMC (30 Dor)

• Maser astrophysics: e.g. intraday variable (tiny structure and turbulence, beaming)

• Stellar physics: acceleration3

H2O masers in LMC

420 μas/yr

LMC center and motion

14 H2O masers with Sν >1 Jyin LMC(Katayama & Imai

2008, in prep)

Measurable:LMC/SMC 3D motionsLMC rotation parallax

c.f. 21 field (around QSO)HST astrometry with

1.1—2.8 yr baselines,

σv~100 km/s(σerr~50 km/s)(Piatek et al. 2008)

4

LMC galactic rotation curve and peculiar motions

5

Residual from rotation curve: σerr~50 km/sPiatek et al. 2008

LMC galactic rotation curve and its deviations 2D deviations from rotation curve

Forecast of GAIA astrometryhttp://www.esa.int/esaSC/120377_index_0_m.html

• 10 μas-level astrometry for 109 stars• σπ~24 μas

for V=15 mag• σπ~44 μas

for V=18 mag(Mignard et al. 2003)• optical-band

astrometry, away fromGalactic disk

• Launch around 2012?

(Lindegren et al. 2007)

Piatek et al. 2008

6

Technical feasibilitySee Y. Asaki’s simulation (Asaki et al. 2007)• (u,v) plane coverage (changing with ~3 yr period)• antenna fast switching (~1 min possible with LBA)• targetー reference separation (<1° ?)• ASTRO-G orbit accuracy (~10 cm)Other issues• scheduling for astrometry• maser feature structure• maser feature lifetime

7

€

σθ ≈0.5θ

RSN

× f

RSN ≥10, θ ≈100μas, 1 ≤ f ≤ 2

Astrometric accuracy

When observed for parallax measurement?• Peaks of the annual parallax ellipse: 2 seasons/year• Tracing maser trajectory: 3 epochs/season

or reliable measurements of the ellipse peak: 2 epochs/season• Longer time baseline for ellipse reconfirmation: 2—3 years

Sgr B2 H2O maser astrometry with VLBA(Reid et al. 2009)

Most suitable:18 epochs/3 years

8

(u,v) plane coverage (24 hr) for LMC

• Always (u,v) hole• Poor coverage for

~4 months every 3 years

• Case with only Usuda tracking station– Only in the first

year for available monthly monitoring

– valid observation in every 3-4 days

9

Snap-shot detection confirmation with ATCA

• Quick look of phase stability in 10 sec integration integration: 1σ ~ 2 mJy @K-band

63 sources (K-band) 45 sources (K-band)σ(Tb)~7 K (R~0.2 pc)

10

Katayama & Imai (2010 in prep.)

VSOP-2 beam(for LMC @48 kpc)

H2O maser spots and features in W3 IRS5 @2 kpc (Imai et al. 2002)

Unique angular resolution for crowded H2O maser features

D>10 kpc for VSOP-211

Requested hours of observations• Annual parallax measurements in LMCN113 (〜 50 Jy) ー J0518-6935 (〜 40 mJy) Δθ=0°.51

In-beam astrometry possible with new reference?HII-1186 (〜 3Jy) ― J0440-6952 (〜 160 mJy) Δθ=1°.3404521-6928 (〜 3Jy) ― J0440-6952 Δθ=1°.08

In-beam astrometry possible with new reference?12 hours × 18 epochs × 2 sources =432 hours

• Proper motion measurements in LMC (maserー QSO)12 hours × 5 epochs × 10 sources =600 hours

• Proper motion measurements in SMC (maserー QSO)S7 (〜 5 Jy) ー J0028-7045 (〜 80 mJy) Δθ=0°.20

12 hours × 5 epochs × 4 sources =240 hours• Star burst region (30 Dor, maserー QSO, in-beam

masers)12 hours × 7 epochs × 1 sources =84 hours

~1400 hours

12

Supplements

13

scientific feasibility of study on H2O masers(supplement)1. Physics of astrophysical masers

– excitation, amplification, beaming, saturation, polarization– Intraday variation has been reported.– technical requirement: resolving fine structures (<10-2 AU) in

the whole maser gas clump (~100 AU)• high quality imaging (dynamic range > 10,000, 10 ≦ B ≦ 10,000 km)• snapshot (< 1 hour) imaging

• Stellar physics explored with H2O masers– earliest phase since birth of star

• “micro-jet” (e.g. Furuya et al. 2000)• circular “bubble” (e.g. Torrelles et al. 2001)

– final phase before death of star• H2O molecules in a planetary nebula (e.g. Miranda et al. 2001)• “water fountain” (e.g. Imai et al. 2002)• stellar shock waves in envelope (Imai et al. 2003)

1. high resolution exploration (with VSOP-2)• acceleration (rotation/helical motion, accretion, deceleration) 14

scientific feasibility of study on H2O masers(today’s main)

3. Maser astrometry– Current trigonometric distance scale < diameter of the Galaxy

• IRAS 19134+2131: D=8.0+0.9-0.7 kpc (Imai et al. 2007)

• S269: D=5.29+0.49-0.41 kpc (Honma et al. 2007, c.f. Reid et al. 2009)

• Sgr B2: D=7.9+0.8-0.7 kpc (Reid et al. 2009)

c.f. BeSSeL project for MW (Reid et al. in VLBA Large Project)– Current proper motion measurements

• For Galactic thin disk components: too large θ0 argument (Reid et al. 2009)peculiar motions by up to 30 km/s (Baba et al. 2009)• proper motions of M33: 54±12 μas yr-1, 3-year baseline (Brunthaler et al. 2005)• orbit and mass of stellar objects in H2O maser sources

(e.g., Imai et al. 2007)– Targets of VSOP-2

• trigonometric distance scale over 10 kpc• proper motions of 100 μas yr-1 in 1 year baseline 15

Geometrical distance measurements: always technical challenging

Previous results Maser astrometry results or goals

R0 D=8.24±0.50 kpc Mira variables(Matsunaga et al. 2009)

D=7.9+0.8-0.7 kpc trogonometric

parallax (Sgr B2, Reid et al. 2009)

D=8.07±0.45 kpc Stellar orbit statistics(Ghez et al. 2008)

D=8.4±0.6 kpc global model fitting (Reid et al. 2009)

D=7.94±0.63 kpc Pop. II Cepheids & RR Lyrs(Groenewegen et al. 2006)

D=7.1±1.5 kpc Expanding flow parallax (Sgr B2N&M, Reid et al. 1988)

D=7.52±0.45 kpc Red clump stars(Nishiyama et al. 2006)

D(LMC)

D=52.0+3.5-3.2 kpc RR Lyrs

(Szewczyk et al. 2008) Annual parallax with VSOP-2Marginal detection (σD/D~30%)

D=47.9±1.1 kpc Chepheids(Szewczyk et al. 2008)

LMC rotation parallax σD/D~10%

D=51.7±2.3 kpc SN1987A expansion(Panagia 1991)

(supplement)

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Galactic rotation deviation rather than Galactic rotation curve• Galactic parameters

– VERA: ~500 masers– VLBA/BeSSeL:

~500 masers• Galactic rotation curve

derive up to 60 kpc – e.g., 2,400 BHB stars

in SDSS DR6 (Xue et al. 2008)

• Deviation from the Galactic rotation curve– e.g. Baba et al. 2009

(supplement)

17

Scientific feasibility of study on H2O masers in Magellanic Clouds

• unique targets for VSOP-2 (θbeam〜 100 μas)

Three major goals• LMC galactic rotation and rotation

deviation• Orbits of MCs around MW• diagnosing interior of star burst activityTrial: annual parallax detection (π~20μas)

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Solving fundamental parameters of galactic kinematics (flat rotation)

free parameters in galactic kinematics (Np = 10)• dynamical center (Xg, Yg, Zg): scaled by distance D• secular motion (Vxg, Vyg, Vzg) : scaled by distance D• rotation axis (ig, PAyg) : linked with D • rotation parameter (Vrot (r=rg), dVrot/dr) : linked with D observables from maser sources (3 × Nmaser)• 3D velocity vector (μx, μy, Vz)(x, y)

freedom of best-fitting: Nf = 3 × Nmaser- Np >> 1

estimation of location along line-of-sight

€

′ f zi( )∂χ 2

∂zi

= 019

LMC galactic rotation• Kinematic center: well known

– α= 05h17m. 6, δ=-69°02’ [J2000] (Kim et al. 1998)• Systemic line-of-sight velocity: well known

– Vsyshelio=279 km/s (Kim et al. 98), 274 km/s (Luks & Rohlfs 1992)

• Rotation axis inclination: well known– 31°.3±3°.5 (Subramaniam & Subramaniam 2009)– 30°.7±1°.1 (Nikoraev et al. 2004) – 34°.7±6°.2 (van der Marel & Cioni 2001), 22°±6° (Kim et al. 1998)

• Rotation axis position angle: varying with radius– 52°ー 77° (e.g., Caldwell 1986)

• Rotation curve: depending on population– HI map: 60ー 70 km/s @275’ (Kim et al. 1998)– HST images: 120±15 km/s @275’ (Piatek et al. 2009)

• How large deviation from the rotation curve?– 10ー 30 km/s in MW (Reid et al. 2009; Asaki et al. 2009)⇒ 40―130 μas/yr @LMC/SMC 20

HST proper motion measurements(after subtracting the center-of-mass space

velocity)

21 fieldsCenter (α,δ)=(5h27m.6, -69°52.2’)

Piatek et al. 2008

21

Dynamics of the Milky Way system (DMW > 50 kpc)

• Secular (proper) motion of LMC : roughly known– (μα, μδ)= (1.956 ± 0.036 , 0.435 ± 0.036) [mas/yr] (Piatek et al. 2008)

– (μα, μδ)= (1.94 ± 0.29 , -0.14 ± 0.36) [mas/yr] (Kroupa & Bastian 1997)

• Systemic line-of-sight velocity: well known– Vsys

helio=279 km/s (Kim et al. 98), 274 km/s (Luks & Rohlfs 1992)

• LMC gravitationally bound by the Milky Way?

– Dependent on the Milky Way rotation velocity (V0~230 km/s or 250 km/s?)

– LMC: gas rich galaxy should be less interacted with the Milky Way

Shattow & Loeb (2009) 22

3D internal motions ofindividual H2O maser sources

M33 @800 kpc(Argon et al. 2004)

ΔT=14 yr

10 km/s 40μas/yr⇒ ⇒ 10μas/3 months

more than 20 proper motions for kinematic model

fitting

c.f. σerr~3 km/s from 64 motions

(Imai et al. 2000)23

H2O masers in 30 Dor (N157A)

• Survey of Oliveira et al. (2006)– 3, 1, 0.4, 0.4 Jy

(75 Jy @10 kpc << H2O masers in

W49N)– Δv~20 km/s– compressed interface

regionsFeedback process for

star formation?

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diagnosing interior of star burst activity30 Dor (N157A, 159, 160)

• 3D internal motions in individual H2O maser sources– Finding the youngest site of massive star formation– Dynamical time scale of the outflow interaction

• 3D relative motions among H2O maser sources– Motions of YSO in GMC: cloud-cloud collision?

• GMC motion in LMC: tracing the possible trigger of star burst?

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26

H2O masers in LMC

ATCA archive(Katayama & Imai 2008) 27

H2O masers in SMC

ATCA archive(Katayama & Imai 2008) 28

H2O masers in LMC & SMC

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Pre-lunch study/ preparation (planning)• VSOP-2 action items

– Reference source candidate survey• 22 GHz and 43 GHz surveys wit ATCA (in processing)• Candidate detection and position measurements with LBA

– fixing possible observation schedule – tracing astrometry activity– VLBI astrometry demo with LBA– VSOP-2 astrometric calibration scheme

• Scientific driving– dynamics of the Local Group– dynamics of star burst region (without AGN)– star formation in metal-poor environment

30

CH3OH masers?• 4 sources

(Green+2009)– Brightest: 3.8 J

in IRAS 05011-6815

(without H2O maser)

– >0.3 JyN11/MC18N105/MC23N160a/MC76

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How is seen?

galactic rotation vectordepending on the location in LMC(~400μas/yr)

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Collaboration with LBA

• Hartebeesthoek (South Africa) may be valid.• eVLBI network completed

– Remote (internet) operation– Software correlation

• Slow antenna slew (0°.2/s in Parkes), but 1 min switching is possible

• SKA high-band after 2020

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Scientific feasibility of MC astrometry• unique targets for VSOP-2 (θbeam〜 100 μas)

– Most feasible at 10 kpc < D < 40 kpc (Asaki priv. comm.)

Three major goals• galactic rotation and rotation deviation

– 21 ~30⇒ ー 40 proper motions • dynamics of the Milky Way system• diagnosing interior of star burst activity

– “local” gas dynamics (bubble, cloud collision)– YSO outflow activity

Trial: annual parallax (π~20μas) 34

Calculation of VLBI array sensitivity

1. Baseline sensitivity

1. Array sensitivity (see VSOP Proposer’s Guide)

For the case with same sensitivity telescopes like VLBA 　　　　　　　　　

※(effective) VSOP-2 sensitivity: only using ASTRO-G – GRT baselines

€

σ ij =1

η c

SEFDiSEFD j

2Bτ

€

σA = wk2σ k

2

k=1

NB∑ wkk=1

NB∑ for k - th baseline

€

σA =σ

NANT NANT −1( ) 2

35

Calculation of “effective” VSOP-2 sensitivity

€

σA =SEFDASTRO−G

η c 2Bτ

wk2SEFDkk=1

Nant∑wkk=1

Nant∑ for k - th baseline

σ A =SEFDASTRO−G

η c 2Bτ

SEFDkk=1

Nant∑Nant

when wk =1

36

ASTRO-G astrometry• Antenna nodding:

period <1 min (~15 sec on-source)• (effective) coherent integration is limited by

(see, e.g. Proposal of VSOP-2 Project, 2003) 1. Atmospheric fluctuation

(tint<90 min, for antenna nodding)2. Systematic phase error due to uncertainty in

ASTRO-G orbits (tint<90 min)• Large telescopes (e.g. NRO 45m) are also useful.• ASTRO-G baselines available after calibration of

ASTRO-G’s complex gain.• News: HartRAO may be available at 22GHz.

(sensitivity equivalent to Ceduna 25m?)37

ASTRO-G (SEFD=5000 K)に対する感度

VERA20m

VLBA25m

NRO45m

NICT34m

ATCA6x20m

Mopra20m

DSN70m

Parkes70m

Ceduna25m

Hobart26m

SEFD[Jy]

1760(Tsys= 100K)

500(Tsys=50K)

280 1300(Tsys=150K)

88 900 60 810 2500 1800

15s256MHz[mJy]

48 26 19 42 11 35 9 33 58 49

15s31.2kHz[Jy]

4.4 2.3 1.7 3.8 0.98 3.1 0.81 3.0 5.2 4.4

90m31.2kHz[Jy]

0.23 0.12 0.09 0.20 0.05 0.17 0.04 0.16 0.28 0.23

位相準拠積分に使える参照電波源 7σ > 230(Parkes)-400 mJyメーザー源による逆位相補償の場合 7σ > 36 Jy基線感度： 7σ > 2.0 Jy

38

ASTRO-G (SEFD=8200 K)に対する感度

VERA20m

VLBA25m

NRO45m

NICT34m

ATCA6x20m

Mopra20m

DSN70m

Parkes70m

Ceduna25m

Hobart26m

SEFD[Jy]

1760(Tsys= 100K)

500(Tsys=50K)

280 1300(Tsys=150K)

88 900 60 810 2500 1800

15s256MHz[mJy]

62 33 25 53 14 44 11 42 74 63

15s31.2kHz[Jy]

5.6 3.0 2.2 4.8 1.3 4.0 1.0 3.8 6.7 5.7

90m31.2kHz[Jy]

0.30 0.16 0.12 0.25 0.07 0.21 0.05 0.20 0.35 0.30

位相準拠積分に使える参照電波源 7σ > 300(Parkes)-520 mJyメーザー源による逆位相補償の場合 7σ > 47 Jy基線感度 7σ > 2.4 Jy

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ASTRO-G 基線群のみによるメーザーマッピング感度 (90

min)LBA fullATCA, MopraDSN70mParkes, Hobart,Ceduna, HartRAO

LBA nominalATCA, MopraParkes, HobartCeduna, HartRAO

EAVN fullVERA, KVN, NRO, NICTShanghaiUrmqui

EAVN nomimalVERA, NICTYamaguchiShanghaiUrmqui

APT=EAVNnominal+ LBAnomimal

ASTRO-GSEFD =5000K[mJy]

73 85 69 85 61

ASTRO-GSEFD =8200K[mJy]

94 109 88 110 78

10-σ 検出レベル：　 0.8 Jy (APT) ― 1.1 Jy (LBA nominal)10-σ 検出レベル：　 0.6 Jy (APT) ― 0.8 Jy (LBA nominal)40

メーザー源フラックス密度の扱い

• 典型的な水メーザースポットサイズ： ~1AU– 10 kpc 先で 100μas ASTRO-G ⇒ 基線での角分解能– LMC&SMC以遠では分解されないとする– 10 kpc 以遠の銀河系内メーザー源：　

相関フラックスは一律 10%程度と仮定する(fakesat simulation より )

• コヒーレンスロスによる相関フラックス低下– Coherency: ρ > 0.8 を仮定– 実質的な coherence integration < 90 min (for ~300 min obs.)⇒ASTRO-G 周回周期 (~6 hours)

• LMC&SMCでは 0.8 Jy 以上のメーザー源がターゲット

• MW(D>10 kpc)では 8.0 Jy 以上がターゲット 41

LMC & SMC の水メーザー源

1 Jy 以上の水メーザー源

14/ 18 in LMC 5/ 6 in SMC

42

ATCA K/Q reference source survey• instruments and observations

• Project code: C2049• 6 telescope @K-band 5 telescopes @Q band• June 12 for ~8 hours for K–band• June 13 for ~6 hours for Q-band, for ~3 hours for K-band• CABB (Compact Array Broadband Backend)

– 2 GHz band width, RCP&LCP, 2 IFs– 19 & 23 GHz or 43 & 45 GHz

• 2 min/scan• 15 baselines (10 baselines) × 2ー 3 scans for imaging

• Source selection– AT20G (14 targets), 15 sources included in current survey– Sydney University Molonglo Sky Survey (SUMSS) @0.84 GHz– Parkes- MIT-NRAO Radio Survey (PMN) @4.85 GHz– 106 targets at K-band– 〜 60 targets at Q-band from detected K-band targets 43

References for LMC&SMC (supplement)• 0530-727 0.21 Jy/beam@X (Ohja et al. 2005, ICRF)• 0530-727 J0529-7245 0.31 Jy@X 25-50Mlambda (0.55Jy) 0.5 Jy @20GHznearest H2O maser: 05406-7111, 7.8 Jy, 1.78 deg away (Katayama&Imai 2008)

• J0542-735 (Fey et al. 2004) 0.2 Jy (2.3GHz), 0.3 Jy (8.4GHz) nearest H2O maser: 05406-7111, 7.8 Jy, 2.37 deg away (Katayama&Imai 2008)

• 0026-710 J0028-7045 0.09 Jy@X 25-50Mlambda 0.3 Jy @20GHzwith S7, 7.4 Jy, 2.01 deg away (Katayama&Imai 2008)• 0424-668 J0425-6646 0.15 Jy@X 25-50Mlambda 0.2 Jy @20GHz• 0441-699 J0440-6952 0.23 Jy@X 25-50Mlambda (0.51Jy) 0.6 Jy @20GHz with HII-1186: 5.0 Jy, 1.34 deg away (Katayama&Imai 2008) with 04521-6928, 2.5 Jy, 1.08 deg away (Katayama&Imai 2008) with N113, 73.8 Jy, 2.87 deg away • 0517-726 J0516-7237 0.16 Jy@X 25-50Mlambda 0.07 Jy @20GHz• 0518-696 J0518-6935 0.04 Jy@X 25-50Mlambda 0.15 Jy @20GHzwith N160A(30Dor), 3.7 Jy, 1.86 deg away, with N113, 30-80 Jy, 0.50 deg away • 0534-723 J0533-7216 0.06 Jy@X 25-50Mlambda 0.2 Jy @20GHz with 05406-7111, 7.8 Jy, • 0530-727 J0529-7625 0.31 Jy@X 25-50Mlambda

44

VSOP-2 astrometry requirement steps• Least requirement: successful astrometry with space mission for one source

– Focused emission on the phase-referenced image (σ~10μas)– at least 4 epochs for a proper motion measurement

• Official requirements:– Proper motion measurements for 9 regions at 5 epochs– Exploration of 30 Dor (N157A) at 5 epochs

• Full requirements: two directions– Trial of trigonometric parallax measurements at 18 epochs– Increase in source number of proper motion measurements

up to 19 sources

45

VSOP-2 target candidates in the Milky Way

• Outer Galaxy in northern sky (Dkin>9 kpc): 7 sources in VERA target catalog (Nakanishi et al. 2009)

• Outer Galaxy behind the Galactic Center: unknown number necessity of proper motion surveys in the southern sky

(c.f. Hachisuka et al. 2009) e.g. IRAS 17599-2148, W31 (2), 01221-0010, 01222-0012, W33B,

01387+0028, W43(M3), 18479-0005, S76 W, W49N• Proper motions of the nearby Galaxy: M33, IC10

(Brunthaler et al. 2005)• Mira variables at the outer thick disk: unknown number necessity of water maser surveys towards the SiO maser

sources (Aarao et al. 2008)• Maser astrophysics: e.g., W3(OH), W3 IRS5, Orion KL, W51 N&M• Stellar physics: e.g, WB724 (star formation), IRAS 18460-0151 (stellar jet)

46