1. Shunya Takekawa T. Oka, K. Tanaka, K. Miura, H. Suzuta Keio University
Millimeter-Wave Molecular Line Observations of the Galactic Circumnuclear Disk
Shunya Takekawa
T. Oka, K. Tanaka, K. Miura, H. Suzuta
Keio University

2. The Galactic Circumnuclear Disk
(CND)
HCN 1–0
2 pc radius ring
Rotating velocity: ~110 km/s
Density: ~104–6 cm–3
Mass: ~104–5 M☉
The entity of the CND is possibly an infalling disk with a diameter of 10 pc (e.g. Oka et al. 2011)
contour: 5 GHz continuum

3. The Galactic Circumnuclear Disk
(CND)
HCN 1–0
2 pc radius ring
Rotating velocity: ~110 km/s
Density: ~104–6 cm–3
Mass: ~104–5 M☉
The entity of the CND is possibly an infalling disk with a diameter of 10 pc (e.g. Oka et al. 2011)
mostly neglected!
contour: 5 GHz continuum
red shift (VLSR=+80 – +110 km/s)
Sgr A*
~ 10 pc
Single-dish obs.
CO 1–0
(Serabyn et al. 1986)
blue shift (VLSR= –80 – –110 km/s)

4. The Galactic Circumnuclear Disk
How is the CND affected by nuclear activities?
How does the CND feed the nucleus?
How was the CND formed?
How is the physical condition?
etc…

5. The Galactic Circumnuclear Disk
In order to answer these questions,
it is essential to reveal the accurate distribution.

6. The Galactic Circumnuclear Disk
In order to answer these questions,
it is essential to reveal the accurate distribution.
SINGLE DISH!
ASTE 10 m
NRO 45 m

7. The Galactic Circumnuclear Disk
In order to answer these questions,
it is essential to reveal the accurate distribution.
appropriate tracer +
SINGLE DISH!
ASTE 10 m
NRO 45 m

8. To search appropriate tracers of the CND,
We conducted 3 mm band spectral line surveys toward the CND and Sgr A* with the NRO 45 m. (Takekawa et al. 2014)
50 lines were detected
TZ1 receiver + SAM45
frequency : 81 – 116 GHz
resolution : 15” –19”

9. We classified the detected lines into three types:
CND-type: mainly trace the CND
GMC-type: mainly trace the GMCs (50 km/s and 20 km/s clouds)
HBD-type: hybrid between the CND- and GMC-types

10. HCN H13CN HCO+ H13CO+ CN SiO CH3OH HC3N N2H+ CS C2H SO c-C3H2
We classified the detected lines into three types:
CND-type: mainly trace the CND
GMC-type: mainly trace the GMCs (50 km/s and 20 km/s clouds)
HBD-type: hybrid between the CND- and GMC-types CS
C2H SO
c-C3H2

11. OTF mapping of the CND HCN H13CN HCO+ H13CO+ CN SiO CH3OH HC3N N2H+ CS
We classified the detected lines into three types:
CND-type: mainly trace the CND
GMC-type: mainly trace the GMCs (50 km/s and 20 km/s clouds)
HBD-type: hybrid between the CND- and GMC-types CS
C2H SO
c-C3H2

12. The OTF mapping of the CND with the NRO 45 m
date: 2014/2/5 – 2/12, 3/28 – 3/30 (33 hr)
line: HCN 1–0, HCO+ 1–0, SiO 2–1, CS 2–1, etc…
mapping range: 6’×6’
angular resolution: ~19”
receiver: TZ1 H/V
spectrometer: SAM45
bandwidth: 1 GHz (resolution: kHz)

13. HCN 1–0 integrated intensity map
Result
HCN 1–0 integrated intensity map
2-pc ring
Negative Longitude Extension
+50 km/s cloud
+20 km/s cloud

14. The velocity structure
VLSR= –150 〜 +150 km/s
HCN 1–0

15. The velocity structure
VLSR= –150 〜 +150 km/s
–150 〜 –20 km/s, +80〜+150 km/s
HCN 1–0
HCN 1–0

16. C1 cloud and Negative Longitude Extension (NLE)
VLSR= –150 〜 –20km/s
–150 〜 –20 km/s, +80〜+150 km/s
HCN 1–0
HCN 1–0

17. C1 cloud and Negative Longitude Extension (NLE)
VLSR= –150 〜 –20km/s
–150 〜 –20 km/s, +80〜+150 km/s
HCN 1–0
HCN 1–0
mostly neglected in recent studies!
first reported in Oka et al. 2011

18. New discovery 1

19. A velocity structure of the C1 cloud
New discovery 1
A velocity structure of the C1 cloud
VLSR= –150 〜 –20km/s
HCN 1–0

20. A velocity structure of the C1 cloud
New discovery 1
A velocity structure of the C1 cloud
VLSR= –150 〜 –20km/s
HCN 1–0
VLSR= –150 〜 –20km/s
CS 2–1

21. A velocity structure of the C1 cloud
New discovery 1
A velocity structure of the C1 cloud
VLSR= –150 〜 –20km/s
HCN 1–0
CND
C1 cloud
The C1 cloud is associated with the CND!
VLSR= –150 〜 –20km/s
CS 2–1
CND
C1 cloud

22. New discovery 2

23. A streamer from the +20 km/s cloud to the CND
New discovery 2
A streamer from the +20 km/s cloud to the CND
VLSR= –150 〜 –20km/s
HCN 1–0
VLSR= –150 〜 –20km/s
CS 2–1

24. A streamer from the +20 km/s cloud to the CND
New discovery 2
A streamer from the +20 km/s cloud to the CND
VLSR= –150 〜 –20km/s
HCN 1–0
CND
+20 km/s cloud
VLSR= –150 〜 –20km/s
CS 2–1
CND
+20 km/s cloud

25. A streamer from the +20 km/s cloud to the CND
New discovery 2
A streamer from the +20 km/s cloud to the CND
VLSR= –40 〜 +10km/s
CS 2–1
CND
+20 km/s cloud

26. A streamer from the +20 km/s cloud to the CND
New discovery 2
A streamer from the +20 km/s cloud to the CND
VLSR= –40 〜 +10km/s
CS 2–1
CND
+20 km/s cloud
A streamer feeding the CND from the +20 km/s cloud

27. A streamer from the +20 km/s cloud to the CND
New discovery 2
A streamer from the +20 km/s cloud to the CND
VLSR= –40 〜 +10km/s
CS 2–1
CND
+20 km/s cloud
+50 km/s
cloud
A possible scheme of the central environment
2-pc ring
CND
seen from the Galactic north pole ★
NLE
The +20 km/s cloud may be feeding the CND through the NLE
streamer
to observer
molecular ridge
+20 km/s cloud

28. Conclusion We found that
The C1 cloud is associated with the CND
The +20 km/s cloud may be feeding the CND through the NLE
Single dish observations are very important for studies of the CND!
A possible scheme of the central environment
VLSR= –150 〜 –20km/s
HCN 1–0

29. Future works
HCN 4–3
HCN 1–0
Detailed analysis
line ratios
estimation of physical parameters
We have already obtained the J =4–3 lines of HCN and HCO+ using the ASTE 10 m
Data reduction of the ASTE observations
We have conducted spectral line surveys
in 330 – 360 GHz band with the ASTE 10 m
Using the single-dish data, we will make efforts to reveal the actual entity of the CND

30. A possible scheme of the central environment
Summary
HCN 1–0
We conducted the OTF mapping observations of the Galactic CND with the NRO 45 m
We found that
The C1 cloud is associated with the CND
The +20 km/s cloud may be feeding the CND through the NLE
Single dish observations are very important for studies of the CND!
A possible scheme of the central environment