Disentangling the Circumnuclear Environs of Centaurus A. III. An Inner Molecular Ring, Nuclear Shocks, and the CO to Warm H{sub 2} Interface
- National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
- Academia Sinica, Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)
- Sterrewacht Leiden, Leiden University, P.O. Box 9513, 2300 RA, Leiden (Netherlands)
- Max Planck Institute for Astronomy (MPIA), Königstuhl 17, D-69121 Heidelberg (Germany)
- Joint ALMA Observatory, Alonso de Córdova, 3107, Vitacura, Santiago 763-0355 (Chile)
- Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121, Bonn (Germany)
- Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
- Department of Earth and Space Sciences, Chalmers University (Sweden)
- National Radio Astronomy Observatory, Socorro, NM (United States)
- Gemini Observatory, 670 N’Aohoku Pl, Hilo 96720-2700, Hawaii, HI (United States)
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)
We present the distribution and kinematics of the molecular gas in the circumnuclear disk (CND; 400 pc × 200 pc) of Centaurus A with resolutions of ∼5 pc (0.″3) and shed light onto the mechanism feeding the active galactic nucleus (AGN) using CO(3–2), HCO{sup +}(4–3), HCN(4–3), and CO(6–5) observations obtained with ALMA. Multiple filaments or streamers of tens to a hundred parsec scale exist within the CND, which form a ring-like structure with an unprojected diameter of 9″ × 6″ (162 pc × 108 pc) and a position angle P.A. ≃ 155°. Inside the nuclear ring, there are two leading and straight filamentary structures with lengths of about 30–60 pc at P.A. ≃ 120° on opposite sides of the AGN, with a rotational symmetry of 180° and steeper position–velocity diagrams, which are interpreted as nuclear shocks due to non-circular motions. Along the filaments, and unlike other nearby AGNs, several dense molecular clumps present low HCN/HCO{sup +}(4–3) ratios (≲0.5). The filaments abruptly end in the probed transitions at r ≃ 20 pc from the AGN, but previous near-IR H{sub 2}( J = 1–0)S(1) maps show that they continue in an even warmer gas phase ( T ∼ 1000 K), winding up in the form of nuclear spirals, and forming an inner ring structure with another set of symmetric filaments along the N–S direction and within r ≃ 10 pc. The molecular gas is governed primarily by non-circular motions, being the successive shock fronts at different scales where loss of angular momentum occurs, a mechanism that may feed efficiently powerful radio galaxies down to parsec scales.
- OSTI ID:
- 22663404
- Journal Information:
- Astrophysical Journal, Vol. 843, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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