Absolute proper motion measurement of Sgr D HII region with VERA

Absolute proper motion measurement of
Sgr D HII region with VERA
Daisuke Sakai(Univ. of Tokyo), Mareki Honma, Tomoaki Oyama,
Takumi Nagayama, Hideyuki Kobayashi(NAOJ)
14年10月28日火曜日
Outline
・Introduction
- the Galactic Center and my long-term goal
- Sgr D region
・Observations
・Results
- Maser distributions and proper motions of Sgr D HII region
・Discussion
- Distance to Sgr D HII region
・Summary
14年10月28日火曜日
Introduction
The Galactic Center
・Center of the Galaxy
・SMBH 4 106M◉
・Peculiar sources
Sgr D
-Sgr B2
-Sgr C
-Sgr D
・Central Molecular Zone(CMZ)
-Molecular ring at 300 pc radius
-Mass reservoir toward the center
-Outstanding non-circular motion
14年10月28日火曜日
Larosa 2000
Motion of CMZ region
・Resonance orbit model
-ILR due to bar potential
-x1 and x2 orbit family
(Binney et al. 1991)
・Expanding ring model
-Due to past Sgr A* activity
(Kaifu et al. 1972)
Measuring proper motion with VLBI is
important to distinguish two models.
14年10月28日火曜日
Velocity
Introduction
Sun
longitude
How can we distinguish 2 models?
Expading Ring Model
Longitude v.s. line-of-sight velocity
200
0.4
150
100
0.2
Vlsr(km/s)
Y(kpc)
50
0
(1)Expanding ring model
0
-50
(2)Resonance orbit model
-0.2
-100
long
Observer
LSR
-0.4
-0.4
-0.2
0
X(kpc)
0.2
-150
-200
0.4
Resonance Orbit Model
3
2
1
0
-1
Galactic Longitude(degrees)
-2
-3
2 models fall in same shape.
Longitude v.s. Proper motion
200
0.4
150
In longitude-proper motion
100
0.2
Vlong(km/s)
50
Y(kpc)
In longitude-velocity diagram,
0
diagram, signiﬁcant diﬀerence
0
-50
emerge at outer parts.
-0.2
-100
Observer
-0.4
-150
-200
-0.4
-0.2
0
X(kpc)
0.2
0.4
3
2
1
0
-1
Galactic Longitude(degrees)
-2
-3
These can be distinguished by
measuring proper motion
14年10月28日火曜日
Introduction
Sgr D region
・Galactic longitude l=1.1
・HII region and SNR region
・CS line has been detected
- Velocity=-16 km s-1
- Width=4 km s-1
・H2O maser detected
・Distance
1. CMZ(in GC)
-Star count
2. Disk
-Narrow line width
The Distance has not
been determined yet!
14年10月28日火曜日
Mehringer et al. 1998
HII region
H2O$maser
SNR region
Observations
Telescopes:VERA
Line: Water maser(22 GHz)
Date: 2008-2011(13 epochs)
Mode: 2-beam
・ Sgr D (A-beam)
-Target source
・J1745-2820 (B-beam)
-Position ref. source(QSO)
14年10月28日火曜日
-8
20
-10
10
-12
-14
0
-16
-10
-20
・Bi-polar like
- 60mas(500 AU@8 kpc)
・Expanding
・Red shift on the east
・Blue shift on the west
・Typical internal motion1 mas/yr
- 38 km/s@8 kpc
-18
1 mas/yr
-20
-30
-22
80
60
40
20
R.A. offset (mas)
0
-20
-8
20
-10
Decl. offset (mas)
10
-12
-14
0
-16
-18
-10
-20
-20
1 mas/yr
20
14年10月28日火曜日
LSR velocity (km/s)
30
-22
10
0
-10
R.A. offset (mas)
-20
LSR velocity (km/s)
Maser distribution
Decl. offset (mas)
Results
Results
Absolute proper motion
：Motion relative to position reference source
Fitting Results
Parallax:
Sgr D
0.8
0
0
Distance:
0.6
-2
-4
-6
0.4
Offset (mas)
-2
Offset (mas)
Decl. offset (mas)
0.181 0.076 mas
1
2
-4
-6
5.53 +4.00/-1.63 kpc
0.2
0
Proper mot.(RA dir.):
-0.2
-0.4
-8
-0.6
-8
-10
-0.8
-10
0
-2
-4
R.A. offset (mas)
14年10月28日火曜日
-6
2008 2009 2010 2011 2012
-1
2008 2009 2010 2011 2012
Year
Year
-1.74 0.045mas/yr
Proper mot.(Dec dir.):
-2.83 0.39 mas/yr
Discussion
Motion of Sgr D region
VGC
We calculated its motion on cases that
Sgr D HII region is located on
1. the Galactic Center(D 8 kpc) or
WGC
Sanna+14
UGC
100 km s-1
2. near 3 kpc arm(D 5 kpc)
Proper motion of maser source for 1. and 2.（Units are km s-1）
UGC
VGC
WGC
①D=8 kpc
-24 2.0
140 13
12 10
②D=5 kpc
-50 2.0
75 8.3
7.3 6.4
UGC : Toward GC
VGC : Toward Galactic rotation
WGC : Toward Galactic north pole
14年10月28日火曜日
Discussion Distance to Sgr D region (Disk case)
・Compare with other sources
within 4 kpc from GC (Sanna+2014)
Our results
Sanna et al. 2014
Reid et al. 2009
Sgr D
・Sanna et al. 2014 suggests that
sources in range 2 kpc < R < 4 kpc have
120 km s-1 < VGC < 240 km s-1
Sanna+14
Sgr D
Sgr B2
・If Sgr D is located in this range of
radius VGC for Sgr D is 75 km s-1
200 km s-1
Disk case
Sgr D
G0.09.62+00.19
G010.47+00.02
G10.62-00.38
G012.02-00.03
G023.44-00.18
G023.70-00.19
GC case
Sgr D
Sgr B2
14年10月28日火曜日
R (kpc)
3.0(assumed)
3.4
1.6
3.6
2.1
3.8
3.7
UGC (km s−1 )
-49±2.0
-36±17
30±22
-60±14
26±33
4.7±43
51 ±16
0.3(assumed) -24±2.0
0.1
-18±1.7
VGC (km s−1 )
75±8.3
190±15
120±16
230 ±6.7
220±27
230±18
170±12
WGC (km s−1 )
7.3±6.4
-10±4.1
18 ±1.8
8.1±1.8
1.5±5.8
2.0±3.1
4.6±2.6
140±13
110±5.0
12±10
-38±5.6
This seems not to be plausible
unless Sgr D have large (more
than 50 km s-1) peculiar motion
Discussion
Distance to Sgr D region (GC case)
Expading Ring Model
・Superpose observational data on
two models
Longitude v.s. line-of-sight velocity
200
0.4
150
100
0.2
Sgr B2
Sgr D
This results
Vlsr(km/s)
Y(kpc)
50
0
0
-50
-0.2
-100
long
Observer
LSR
-0.4
-0.4
-0.2
0
0.2
-150
-200
0.4
3
2
1
X(kpc)
Resonance Orbit Model
0
-1
Galactic Longitude(degrees)
-2
-3
・Even if either model adopted,
Sgr D should locate on near
side against GC
Longitude v.s. Proper motion
200
0.4
・Unfortunately, Both results
(This result and Reid+09) could
not act crucial roles to distinguish
two models.
150
100
0.2
Vlong(km/s)
Y(kpc)
50
0
0
-50
-0.2
-100
Observer
-0.4
-150
-200
-0.4
-0.2
0
X(kpc)
0.2
0.4
3
2
1
0
-1
Galactic Longitude(degrees)
-2
-3
We have to increase the number of sources!!
14年10月28日火曜日
Summary
・It is essential to measure absolute proper motions with VLBI
for revealing the dynamics in the center of the Galaxy.
・The distance to Sgr D HII region has not determined yet,
even though This source is one of the brightest radio source
in the Galactic Center.
・We measured absolute proper motion of Sgr D HII region
relative to QSO with VERA
・We estimate the distance by considering the proper motion
in the cases of
①CMZ(R 300 pc) and
②3 kpc arm(R 3 kpc)
・② does not match other measured results
・① is similar to results for Sgr B2, but only two measurement
→We need to increase the number of source
14年10月28日火曜日

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