Comparison of Millimeter-wave and X-Ray Emission in Seyfert Galaxies

Abstract

We compare the emission at multiple wavelengths of an extended Seyfert galaxy sample, including both types of Seyfert nuclei. We use the Caltech Submillimeter Observatory to observe the CO J = 2-1 transition line in a sample of 45 Seyfert galaxies and detect 35 of them. The galaxies are selected by their joint soft X-ray (0.1-2.4 keV) and far-infrared (λ = 60-100 μm) emission from the ROSAT/IRAS sample. Since the CO line widths (W_(CO)) reflect the orbital motion in the gravitational potential of the host galaxy, we study how the kinematics are affected by the central massive black hole (BH), using the X-ray luminosity. A significant correlation is found between the CO line width and hard (0.3-8 keV from Chandra and XMM-Newton) X-ray luminosity for both types of Seyfert nuclei. Assuming an Eddington accretion to estimate the BH mass (M_(BH)) from the X-ray luminosity, the W_(CO)-L_X) relation establishes a direct connection between the kinematics of the molecular gas of the host galaxy and the nuclear activity, and corroborates the previous studies that show that the CO is a good surrogate for the bulge mass. We also find a tight correlation between the (soft and hard) X-ray and the CO luminosities for both Seyfert types. These results indicate a direct relation between the molecular gas (i.e., star formation activity) of the host galaxy and the nuclear activity. To establish a clear causal connection between molecular gas and the fueling of nuclear activity, high-resolution maps (<100 pc) of the CO emission of our sample will be required and provided in a forthcoming Atacama Large Millimeter Array observation.