The molecular polar disc in NGC 2768

Alison F. Crocker (1) , Martin Bureau (1) , Lisa M. Young (1) , Françoise Combes (2, 3)

1 Sub-department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road
2 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
3 Galaxies et cosmologie

We present CO(1-0) and CO(2-1) maps of the molecular polar disc in the elliptical galaxy NGC 2768 obtained at the Institute de Radioastronomie Millimétrique (IRAM) Plateau de Bure Interferometer. The maps have a resolution of and for the CO(1-0) and CO(2-1) lines, respectively. The CO maps complete the unique picture of the interstellar medium (ISM) of NGC 2768; the dust, molecular gas, ionized gas and neutral hydrogen (HI) trace the recent acquisition of cold and cool gas over two orders of magnitude in radii (and much more in density). In agreement with the other ISM components, the CO distribution extends nearly perpendicularly to the photometric major axis of the galaxy. Velocity maps of the CO show a rotating polar disc or ring in the inner kiloparsec. This cool gas could lead to kinematic substructure formation within NGC 2768. However, the stellar velocity field and Hbeta absorption line-strength maps from the optical integral-field spectrograph SAURON give no indication of a young and dynamically cold stellar population coincident with the molecular polar disc. Very recent or weak star formation, undetectable in line strengths, nevertheless remains a possibility and could be at the origin of some of the ionized gas observed. Millimetre continuum emission was also detected in NGC 2768, now one of only a few low-luminosity active galactic nuclei with observed mm continuum emission.

Domaines: Astrophysique [astro-ph]

Alison F. Crocker, Martin Bureau, Lisa M. Young, Françoise Combes. The molecular polar disc in NGC 2768. Monthly Notices of the Royal Astronomical Society, 2008, 386, pp.1811-1820. ⟨10.1111/j.1365-2966.2008.13177.x⟩. ⟨hal-03785443⟩