Post on 27-Jan-2016
description
Millimeter-Wave Molecular Line Observations of the Galactic Circumnuclear Disk
Shunya TakekawaT. Oka, K. Tanaka, K. Miura, H. Suzuta
Keio University
Rotating velocity: ~110 km/sDensity: ~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
The Galactic Circumnuclear Disk
2 pc radius ring
(CND)HCN 1–0
blue shift (VLSR= –80 – –110 km/s)
Rotating velocity: ~110 km/sDensity: ~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
The Galactic Circumnuclear Disk
2 pc radius ring
(CND)HCN 1–0
red shift (VLSR=+80 – +110 km/s)
Single-dish obs.CO 1–0(Serabyn et al. 1986)
~ 10 pcSgr A*
mostly neglected!
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…
The Galactic Circumnuclear Disk
In order to answer these questions, it is essential to reveal the accurate
distribution.
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
The Galactic Circumnuclear Disk
In order to answer these questions, it is essential to reveal the accurate
distribution.SINGLE DISH! appropriate tracer +ASTE 10 m
NRO 45 m
To search appropriate tracers of the CND,
We conducted 3 mm band spectral line surveystoward the CND and Sgr A* with the NRO 45 m.
(Takekawa et al. 2014)
TZ1 receiver + SAM45frequency : 81 – 116 GHzresolution : 15” –19”
50 lines were detected
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
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
HCO+
HCN
SiO CNH13CO+
H13CN
N2H+
CH3OHHC3N
CSSO
C2Hc-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
HCO+
HCN
SiO CNH13CO+
H13CN
N2H+
CH3OHHC3N
CSSO
C2Hc-C3H2
OTF mapping of the CND
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: 244.14 kHz)
ResultHCN 1–0 integrated intensity map
2-pc ringNegative Longitude Extension
+50 km/s cloud+20 km/s cloud
The velocity structureVLSR= –150 〜 +150 km/s
HCN 1–0
The velocity structureVLSR= –150 〜 +150 km/s –150 〜 – 20 km/s, +80 〜 +150 km/s
HCN 1–0 HCN 1–0
C1 cloud and Negative Longitude Extension (NLE)
–150 〜 – 20 km/s, +80 〜 +150 km/sVLSR= –150 〜 – 20km/s
HCN 1–0 HCN 1–0
C1 cloud and Negative Longitude Extension (NLE)
–150 〜 – 20 km/s, +80 〜 +150 km/sVLSR= –150 〜 – 20km/s
first reported in Oka et al. 2011
HCN 1–0 HCN 1–0mostly neglected in recent studies!
New discovery 1
A velocity structure of the C1 cloudVLSR= –150 〜 – 20km/s
HCN 1–0
New discovery 1
A velocity structure of the C1 cloudVLSR= –150 〜 – 20km/s
VLSR= –150 〜 – 20km/s
HCN 1–0
CS 2–1
New discovery 1
A velocity structure of the C1 cloudVLSR= –150 〜 – 20km/s
VLSR= –150 〜 – 20km/s
HCN 1–0
CS 2–1
The C1 cloud is associated with the CND!
CND
CND
C1 cloud
C1 cloud
New discovery 1
New discovery 2
A streamer from the +20 km/s cloud to the CNDVLSR= –150 〜 – 20km/s
VLSR= –150 〜 – 20km/s
HCN 1–0
CS 2–1
New discovery 2
A streamer from the +20 km/s cloud to the CNDVLSR= –150 〜 – 20km/s
VLSR= –150 〜 – 20km/s
HCN 1–0
CS 2–1
+20 km/s cloud
+20 km/s cloud
CND
CND
New discovery 2
A streamer from the +20 km/s cloud to the CNDVLSR= –40 〜 +10km/s
CS 2–1
+20 km/s cloud
CND
New discovery 2
A streamer from the +20 km/s cloud to the CNDVLSR= –40 〜 +10km/s
CS 2–1
+20 km/s cloud
CND
A streamer feeding the CND from the +20 km/s cloud
New discovery 2
CND
A streamer from the +20 km/s cloud to the CNDVLSR= –40 〜 +10km/s
CS 2–1
+20 km/s cloud
★
The +20 km/s cloud may be feeding the CND through the NLE
A possible scheme of the central environment seen from the Galactic north pole
+50 km/s cloud
molecular ridge +20 km/s cloud
to observer
2-pc ring
NLE
streamer
CND
New discovery 2
ConclusionWe found that
1. The C1 cloud is associated with the CND2. The +20 km/s cloud may be feeding the CND
through the NLE
Single dish observations are very important for studies of the CND!
HCN 1–0
VLSR= –150 〜 – 20km/sA possible scheme of the central environment
Future works• 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
HCN 4–3 HCN 1–0
Using the single-dish data, we will make effortsto reveal the actual entity of the CND
Summary• We conducted the OTF mapping
observations of the Galactic CND with the NRO 45 m
• We found that1. The C1 cloud is associated with the
CND2. The +20 km/s cloud may be feeding
the CND through the NLE
• Single dish observations are very importantfor studies of the CND!
HCN 1–0
A possible scheme of the central environment