2013MNRAS.429.2315S -
Mon. Not. R. Astron. Soc., 429, 2315-2332 (2013/March-1)
Kinematics and excitation of the molecular hydrogen accretion disc in NGC 1275.
SCHARWACHTER J., McGREGOR P.J., DOPITA M.A. and BECK T.L.
Abstract (from CDS):
We report the results of high spatial and spectral resolution integral-field spectroscopy of the central ∼ 3x3 arcsec2 of the active galaxy NGC 1275 (Perseus A), based on observations with the Near-infrared Integral Field Spectrograph (NIFS) and the ALTitude conjugate Adaptive optics for the InfraRed (ALTAIR) adaptive-optics system on the Gemini North telescope. The circum-nuclear disc in the inner R ∼ 50 pc of NGC 1275 is seen in both the H2 and [Fe ii] lines. The disc is interpreted as the outer part of a collisionally excited turbulent accretion disc. The kinematic major axis of the disc at a position angle of 68° is oriented perpendicular to the radio jet. A streamer-like feature to the south-west of the disc, detected in H2 but not in [Fe ii], is discussed as one of possibly several molecular streamers, presumably falling into the nuclear region. Indications of an ionization structure within the disc are deduced from the He i and Brγ emission lines, which may partially originate from the inner portions of the accretion disc. The kinematics of these two lines agrees with the signature of the circum-nuclear disc, but both lines display a larger central velocity dispersion than the H2 line. The ro-vibrational H2 transitions from the core of NGC 1275 are indicative of thermal excitation caused by shocks and agree with excitation temperatures of ∼ 1360 and ∼ 4290 K for the lower and higher energy H2 transitions, respectively. The data suggest X-ray heating as the dominant excitation mechanism of [Fe ii] emission in the core, while fast shocks are a possible alternative. The [Fe ii] lines indicate an electron density of ∼ 4000/cm3. The H2 disc is modelled using simulated NIFS data cubes of H2 emission from inclined discs in Keplerian rotation around a central mass. Assuming a disc inclination of 45°±10°, the best-fitting models imply a central mass of (8+ 7- 2) x 108M☉. Taken as a black hole mass estimate, this value is larger than previous estimates for the black hole mass in NGC 1275, but is in agreement with the M-σ relation within the rms scatter. However, the molecular gas mass in the core region is tentatively estimated to be non-negligible, which suggests that the central mass may rather represent an upper limit for the black hole mass. In comparison to other H2-luminous radio galaxies, we discuss the relative role of jet feedback and accretion in driving shocks and turbulence in the molecular gas component.
To bookmark this query, right click on this link: simbad:objects in 2013MNRAS.429.2315S and select 'bookmark this link' or equivalent in the popup menu