Kinetic Energy Transfer from X-Ray Ultrafast Outflows to Millimeter/Submillimeter Cold Molecular Outflows in Seyfert Galaxies

Abstract

UltraFast Outflows (UFOs), seen as X-ray blueshifted absorption lines in active galactic nuclei (AGNs), are considered to be a key mechanism for AGN feedback. In this scenario, UFO kinetic energy is transferred into the cold and extended molecular outflow observed at the millimeter/submillimeter wavelength, which blows away the gas and suppresses star formation and accretion onto the central black hole (BH). However, the energy transfer between the inner UFO and the outer molecular outflow has not yet been fully studied mainly due to the limited sample. In this paper, we perform a comparison of their kinetic energy using the millimeter/submillimeter published data and the X-ray archival data. Among 14 Seyfert galaxies whose molecular outflows are detected in the Institut de RAdioastronomie Millimétrique/Plateau de Bure Interferometer data, 8 targets are bright enough to perform spectral fitting in X-ray, and we have detected UFO absorption lines in 6 targets with a 90% significance level, using XMM-Newton and Suzaku satellites. The time-averaged UFO kinetic energy was derived from the spectral fitting. As a result, we have found that the energy-transfer rate (kinetic energy ratio of the molecular outflow to the UFO) ranges from ∼7 × 10 −3 to ∼1, and has a negative correlation with the BH mass, which shows that the AGN feedback is more efficient in the lower mass BHs. This tendency is consistent with the theoretical prediction that the cooling timescale of the outflowing gas becomes longer than the flow timescale when the BH mass is smaller.