ALMA observations of AGN fuelling: The case of PKS B1718-649

F. M. Maccagni*, R. Morganti, T. A. Oosterloo, J. B. R. Oonk, B. H. C. Emonts

*Corresponding author for this work

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Abstract

We present ALMA observations of the (CO)-C-12 (2-1) line of the newly born (t(radio) similar to 10(2) years) active galactic nucleus (AGN), PKS B1718-649. These observations reveal that the carbon monoxide in the innermost 15 kpc of the galaxy is distributed in a complex warped disk. In the outer parts of this disk, the CO gas follows the rotation of the dust lane and of the stellar body of the galaxy hosting the radio source. In the innermost kiloparsec, the gas abruptly changes orientation and forms a circumnuclear disk (r less than or similar to 700 pc) with its major axis perpendicular to that of the outer disk. Against the compact radio emission of PKS B1718-649 (r similar to 2 pc), we detect an absorption line at red-shifted velocities with respect to the systemic velocity (Delta v = +365 +/- 22 km s(-1)). This absorbing CO gas could trace molecular clouds falling onto the central super-massive black hole. A comparison with the near-infrared H-2 1-0 S(1) observations shows that the clouds must be close to the black hole (r less than or similar to 75 pc). The physical conditions of these clouds are different from the gas at larger radii, and are in good agreement with the predictions for the conditions of the gas when cold chaotic accretion triggers an active galactic nucleus. These observations on the centre of PKS B1718-649 provide one of the best indications that a population of cold clouds is falling towards a radio AGN, likely fuelling its activity.

Original languageEnglish
Article number42
Number of pages12
JournalAstronomy & astrophysics
Volume614
DOIs
Publication statusPublished - 12-Jun-2018

Keywords

  • galaxies: individual: PKS B1718-649
  • galaxies: active
  • galaxies: ISM
  • galaxies: kinematics and dynamics
  • ISM: clouds
  • submillimeter: ISM
  • ACTIVE GALACTIC NUCLEI
  • SUPERMASSIVE BLACK-HOLES
  • COLD MOLECULAR GAS
  • MASSIVE GALAXIES
  • QUASAR FEEDBACK
  • STAR-FORMATION
  • JET POWER
  • RADIO-AGN
  • H I
  • ACCRETION

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