Extragalactic H_2O Megamaser Sources:Central Black Holes,Nuclear X-ray and Maser Emissions

Extragalactic H2O megamasers are typically found within the innermost few parsecs of active galaxy nuclei(AGN) and the maser emission is considered to be excited most likely by the X-ray irradiation of the AGN.We investigate a comprehensive sample of extragalactic H2O masers in a sample of 38 maser host AGN to check potential correlations of the megamaser emission with parameters of the AGN,such as X-ray luminosity and black hole(BH) masses.We find a relation between the maser luminosities and BH masses,LH2O ∝ M B3.H6± 0.4,which supports basically the theoretical prediction.The relation between the maser emission and X-ray emission is also confirmed.

Radio Luminosity,Black Hole Mass and Eddington Ratio for Quasars from the Sloan Digital Sky Survey

We investigate the MBH-σ* relation for radio-loud quasars with redshift z < 0.83 in Data Release 3 of the Sloan Digital Sky Survey(SDSS).The sample consists of 3772 quasars with better models of the Hβ and [OⅢ] lines and available radio luminosity,including 306 radio-loud quasars,3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity(181 radio-quiet quasars with measured radio luminosity).The virial supermassive black hole mass(MBH) is calculated from the broad Hβline,and the host stellar velocity dispersion(σ*) is traced by the core [OⅢ] gaseous velocity dispersion.The radio luminosity and radio loudness are derived from the FIRST catalog.Our results are as follows:(1) For radio-quiet quasars,we confirm that there is no obvious deviation from the MBH-σ* relation defined for inactive galaxies when the uncertainties in MBH and the luminosity bias are concerned.(2) We find that the radio-loud quasars deviate more from the MBH-σ* relation than do the radio-quiet quasars.This deviation is only partly due to a pos-sible cosmological evolution of the MBH-σ* relation and the luminosity bias.(3) The radio luminosity is proportional to M B1.H28 +0.23 -0.16(LBol/LEdd)1.29 +0.31 -0.24 for radio-quiet quasars and to MB3.H10 +0.60 -0.70(LBol/LEdd)4.18 +1.40 -1.10 for radio-loud quasars.The weaker dependence of the ra-dio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities,such as the spin of the black hole.

Feedback of Active Galactic Nuclei in Seyfert 2 Galaxies

It is well accepted that feedback from active galactic nuclei(AGNs) plays an important role in the coevolution of the supermassive black hole(SMBH) and its host galaxy,but the concrete mechanism of feedback remains unclear.A considerable body of evidence suggests that AGN feedback suppresses star formation in the host galaxy.We assemble a sample of Seyfert 2 galaxies with recent observational data of compact nuclear starbursts and estimate the gas surface density as a function of column density to illuminate the relation between feedback and AGN properties.Although there are some uncertainties,our data still imply the deviation from the star formation law(Kennicutt-Schmidt law).Further,they indicate that:(1) Feedback correlates with the Eddington ratio,rather than with the mass of SMBH,as a result of decreasing star formation efficiency.(2) The SMBH and the torus are probably undergoing coevolution.Conclusions presented here can be refined through future high resolution CO or HCN observations.