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 inve...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.展开更多
Detection of γ-ray emissions from a class of active galactic nuclei(viz blazars),has been one of the important findings from the Compton Gamma-Ray Observatory(CGRO).However,their γ-ray luminosity function has not be...Detection of γ-ray emissions from a class of active galactic nuclei(viz blazars),has been one of the important findings from the Compton Gamma-Ray Observatory(CGRO).However,their γ-ray luminosity function has not been well determined.Few at-tempts have been made in earlier works,where BL Lacs and Flat Spectrum Radio Quasars(FSRQs) have been considered as a single source class.In this paper,we investigated the evolution and γ-ray luminosity function of FSRQs and BL Lacs separately.Our investigation indicates no evolution for BL Lacs,however FSRQs show significant evolution.Pure luminosity evolution is assumed for FSRQs and exponential and power law evolu-tion models are examined.Due to the small number of sources,the low luminosity end index of the luminosity function for FSRQs is constrained with an upper limit.BL Lac lu-minosity function shows no signature of break.As a consistency check,the model source distributions derived from these luminosity functions show no significant departure from the observed source distributions.展开更多
We found a NLS1 nucleus in the extensively studied eruptive BL Lac object, 0846+51W1, out of a large sample of NLS1s compiled from the spectroscopic dataset of SDSS DR1. Its optical spectrum can be well decomposed int...We found a NLS1 nucleus in the extensively studied eruptive BL Lac object, 0846+51W1, out of a large sample of NLS1s compiled from the spectroscopic dataset of SDSS DR1. Its optical spectrum can be well decomposed into three components: a power law component from the relativistic jet, a stellar component from the host galaxy, and a component from a typical NLS1 nucleus. The emission line properties of 0846+51Wl, FWHM (Hβ)∽- 1710 km s-1 and [OⅢ]λ5007 /Hβ∽-0.32from its SDSS spectrum observed when it was in the faint state, fulfil the conventional definition of NLS1. Strong FelI emission is detected in the SDSS spectrum,which is also typical of NLS1s. We tried to estimate its central black hole mass using various techniques and found that 0846+51W1 is very likely emitting at a few × 10% of the Eddington luminosity. We speculate that Seyfert-like nuclei, including NLS1s, might be concealed in a significant fraction of BL Lacs but have remained largely unobserved because, often, their optical-UV continuum is overwhelmed by the synchrotron emission.展开更多
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 un...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.展开更多
基金the National Natural Science Foundation of China
文摘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.
文摘Detection of γ-ray emissions from a class of active galactic nuclei(viz blazars),has been one of the important findings from the Compton Gamma-Ray Observatory(CGRO).However,their γ-ray luminosity function has not been well determined.Few at-tempts have been made in earlier works,where BL Lacs and Flat Spectrum Radio Quasars(FSRQs) have been considered as a single source class.In this paper,we investigated the evolution and γ-ray luminosity function of FSRQs and BL Lacs separately.Our investigation indicates no evolution for BL Lacs,however FSRQs show significant evolution.Pure luminosity evolution is assumed for FSRQs and exponential and power law evolu-tion models are examined.Due to the small number of sources,the low luminosity end index of the luminosity function for FSRQs is constrained with an upper limit.BL Lac lu-minosity function shows no signature of break.As a consistency check,the model source distributions derived from these luminosity functions show no significant departure from the observed source distributions.
文摘We found a NLS1 nucleus in the extensively studied eruptive BL Lac object, 0846+51W1, out of a large sample of NLS1s compiled from the spectroscopic dataset of SDSS DR1. Its optical spectrum can be well decomposed into three components: a power law component from the relativistic jet, a stellar component from the host galaxy, and a component from a typical NLS1 nucleus. The emission line properties of 0846+51Wl, FWHM (Hβ)∽- 1710 km s-1 and [OⅢ]λ5007 /Hβ∽-0.32from its SDSS spectrum observed when it was in the faint state, fulfil the conventional definition of NLS1. Strong FelI emission is detected in the SDSS spectrum,which is also typical of NLS1s. We tried to estimate its central black hole mass using various techniques and found that 0846+51W1 is very likely emitting at a few × 10% of the Eddington luminosity. We speculate that Seyfert-like nuclei, including NLS1s, might be concealed in a significant fraction of BL Lacs but have remained largely unobserved because, often, their optical-UV continuum is overwhelmed by the synchrotron emission.
基金the National Natural Science Foundation of China
文摘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.
