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

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

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)

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. appropriate tracer + SINGLE DISH! ASTE 10 m NRO 45 m

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”

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

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

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

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)

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

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

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

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

New discovery 1

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

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

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

New discovery 2

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

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

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 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

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

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

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

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