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Millimeter-Wave Molecular Line Observations of the Galactic Circumnuclear Disk

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). Rotating velocity: ~ 110 km/ s Density: ~ 10 4–6 cm –3 Mass: ~ 10 4–5 M ☉

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Millimeter-Wave Molecular Line Observations of the Galactic Circumnuclear Disk

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

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

  3. The Galactic Circumnuclear Disk (CND) Rotating velocity: ~110 km/s Density: ~104–6 cm–3 Mass: ~104–5M☉ The entity of the CND is possibly an infalling disk with a diameter of 10 pc (e.g. Oka et al. 2011) HCN 1–0 2 pc radius ring 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/sand 20 km/s clouds) • HBD-type: hybrid between the CND- and GMC-types

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

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

  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: 244.14 kHz)

  13. 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) –150 〜 –20 km/s, +80〜+150 km/s VLSR= –150 〜 –20km/s HCN 1–0 HCN 1–0

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

  18. New discovery 1

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

  20. 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. 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. 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. 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. 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. 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. New discovery 2 A streamer from the +20 km/s cloud to the CND VLSR= –40 〜 +10km/s The +20 km/s cloud may be feeding the CND through the NLE CS 2–1 CND +20 km/s cloud A possible scheme of the central environment +50 km/s cloud 2-pc ring • seen from the Galactic north pole CND 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 willmake effortsto reveal the actual entity of the CND

  30. 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 importantfor studies of the CND! A possible scheme of the central environment

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