A very extended molecular web around NGC 1275

¹ LERMA, Observatoire de Paris, UMR 8112 du CNRS, 75014 Paris, France
e-mail: philippe.salome@obspm.fr
² Institut de Radio Astronomie Millimétrique, Domaine Universitaire, 38406 St. Martin d’Hères, France
³ Institute of Computational Cosmology, Durham University, South Road, Durham, DH1 3LE, UK
⁴ IoA, Madingley Road, Cambridge, CB3 OHA, UK
⁵ Laboratoire d’Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, 1290 Sauverny, Switzerland

Received: 12 November 2008
Accepted: 16 May 2011

Abstract

We present the first detection of CO emission lines in the Hα filaments at distances as far as 50 kpc from the centre of the galaxy NGC 1275. This gas is probably dense (≥10³ cm^-3). However, it is not possible to accurately determine the density and the kinetic temperature of this relatively warm gas (T_kin ~ 20–500 K) with the current data alone. The amount of molecular gas in the filaments is large – 10⁹ M_⊙ (assuming a Galactic N(H₂)/I_CO ratio). This is 10% of the total mass of molecular gas detected in this cD galaxy. This gas has large-scale velocities comparable to those seen in Hα. The origin of the filaments is still unclear, but their formation is very likely linked to the AGN positive feedback that regulates the cooling of the surrounding X-ray-emitting gas as suggested by numerical simulations. We also present high-resolution spectra of the galaxy core. The spatial characteristics of the double-peaked profile suggest that the molecular web of filaments and streamers penetrates down to radii of less than 2 kpc from the central AGN and eventually feeds the galaxy nucleus. The mass of gas inside the very central region is  ~10⁹ M_⊙, and is similar to the mass of molecular gas found in the filaments.