Download H 2 O maser

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 28
1
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 formation
critical astrophysical sites: LMC and SMC, (mini) starburst in LMC (30 Dor)
2. Maser astrophysics: e.g. intraday variable
(tiny structure and turbulence, beaming)
3. Stellar physics: acceleration
3
H2O masers in LMC
14 H2O masers
with Sν >1 Jy
in LMC
(Katayama & Imai
2008, in prep)
Measurable:
LMC/SMC 3D motions
LMC rotation parallax
LMC center
and motion
420 μas/yr
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
LMC galactic rotation curve and its deviations
2D deviations from rotation curve
Residual from rotation curve: σerr~50 km/s
Piatek et al. 2008
5
Forecast of GAIA astrometry
http://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
Piatek et al. 2008
(Mignard et al. 2003)
• optical-band
astrometry,
away from
Galactic disk
• Launch around
2012?
(Lindegren et al. 2007)
6
Technical feasibility
See 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 Astrometric accuracy
• maser feature structure

  0.5
f
• maser feature lifetime
RSN
RSN  10,
  100as, 1  f  2
7
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
Most suitable:
18 epochs/3 years
Sgr B2 H2O
maser astrometry
with VLBA
(Reid et al. 2009)
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
σ(Tb)~7 K (R~0.2 pc)
63 sources (K-band) 45 sources (K-band)
Katayama & Imai (2010 in prep.)
10
Unique angular resolution for
crowded H2O maser features
VSOP-2 beam
(for LMC @48 kpc)
H2O maser spots and
features in W3 IRS5
@2 kpc (Imai et al. 2002)
D>10 kpc for VSOP-2
11
Requested hours of observations
• Annual parallax measurements in LMC
~1400 hours
N113 (〜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°.34
04521-6928 (〜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 12
Supplements
13
scientific feasibility of study on H2O masers
1. Physics of astrophysical masers
(supplement)
– 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
2. 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)
– 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
R0
(supplement)
Previous results
Maser astrometry results or goals
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
D=8.4±0.6 kpc global model
fitting (Reid et al. 2009)
(Ghez et al. 2008)
D=7.94±0.63 kpc
Pop. II Cepheids & RR Lyrs
D=7.1±1.5 kpc
(Groenewegen et al. 2006)
(Sgr B2N&M, Reid et al. 1988)
Expanding flow parallax
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)
D=47.9±1.1 kpc Chepheids
(Szewczyk et al. 2008)
D=51.7±2.3 kpc SN1987A expansion
(Panagia 1991)
Annual parallax with VSOP-2
Marginal detection (σD/D~30%)
LMC rotation parallax
σD/D~10%
16
Galactic rotation deviation rather than
(supplement)
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
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 activity
Trial: annual parallax detection (π~20μas)
18
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
2

estimation of location along line-of-sight f z 
0
i
z i
19
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)
20
HST proper motion measurements
(after subtracting the center-of-mass space
velocity)
21 fields
Center (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
– Vsyshelio=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 of
individual H2O maser sources
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)
M33 @800 kpc
(Argon et al. 2004)
ΔT=14 yr
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
regions
Feedback process for
star formation?
24
diagnosing interior of star burst activity
30 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?
25
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
29
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 Jy
N11/MC18
N105/MC23
N160a/MC76
31
How is seen?
galactic rotation
vector
depending on
the location
in LMC
(~400μas/yr)
32
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
33
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
 ij 
1. Baseline sensitivity
1
SEFDi SEFD j
c
2B
1. Array sensitivity (see VSOP Proposer’s Guide)
A 

NB
k1
w
2
k
2
k

For the case with same
sensitivity telescopes like VLBA

NB
k1
wk
A 
for k - th baseline

N ANT N ANT 1 2
※(effective) VSOP-2 sensitivity:
only using ASTRO-G
 – GRT baselines
35
Calculation of “effective” VSOP-2 sensitivity
SEFDASTROG
A 
c 2B
SEFDASTROG
A 
c 2B

N ant
k1


N ant
k1
2
k
w SEFDk
N ant
k1
wk
SEFDk
N ant
for k - th baseline
when w k  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
VERA
20m
VLBA
25m
NRO
45m
NICT
34m
ATCA
SEFD
[Jy]
1760
500
280
1300 88
(Tsys=
100K)
(Tsys=
50K)
15s
256
MHz
[mJy]
48 26 19 42 11 35 9
15s
31.2
kHz
[Jy]
4.4
2.3
1.7
3.8 0.98 3.1
0.81 3.0
5.2
4.4
90m
31.2
kHz
[Jy]
0.23
0.12
0.09
0.20 0.05
0.04
0.28
0.23
6x20m
Mopra DSN
20m
70m
Parkes Ceduna Hobart
70m
25m
26m
900
810
60
2500
1800
(Tsys=
150K)
0.17
33 58 49
0.16
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
38
基線感度： 7σ > 2.0 Jy
ASTRO-G (SEFD=8200 K)に対する感度
VERA
20m
VLBA
25m
NRO
45m
NICT
34m
ATCA
Mopra DSN
6x20m 20m
70m
Parkes Ceduna Hobart
70m
25m
26m
SEFD
[Jy]
1760
500
280
1300
88
810
(Tsys=
100K)
(Tsys=
50K)
15s
256
MHz
[mJy]
62 33 25 53 14 44 11 42 74 63
15s
31.2
kHz
[Jy]
5.6
3.0
2.2
4.8
1.3
4.0
1.0
3.8
6.7
5.7
90m
31.2
kHz
[Jy]
0.30
0.16
0.12
0.25
0.07
0.21
0.05
0.20
0.35
0.30
900
60
2500
1800
(Tsys=
150K)
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
39
基線感度 7σ > 2.4 Jy
ASTRO-G 基線群のみによる
メーザーマッピング感度 (90 min)
LBA full
LBA nominal
EAVN full
ATCA, Mopra
ATCA, Mopra
VERA, KVN,
DSN70m
Parkes, Hobart
NRO, NICT
Parkes, Hobart,
Ceduna, HartRAO Shanghai
Ceduna, HartRAO
Urmqui
EAVN nomimal
VERA, NICT
Yamaguchi
Shanghai
Urmqui
APT
=EAVN
nominal
+ LBA
nomimal
ASTRO-G
SEFD
=5000K
[mJy]
73
85
69
85
61
ASTRO-G
SEFD
=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 @20GHz
nearest 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 @20GHz
with 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 @20GHz
with 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