Many galaxies are thought to contain massive black holes, with masses in excess of ten million solar masses, at their centres and warped circumnuclear toruses. The best evidence comes from observing gas or masers rota...Many galaxies are thought to contain massive black holes, with masses in excess of ten million solar masses, at their centres and warped circumnuclear toruses. The best evidence comes from observing gas or masers rotating rapidly within a circumnuclear torus surrounding a central body. Here we report on the first MERLIN observations of line emission from the OH megamaser toward IRAS 10173+0828. The position of peak flux contours of the OH megamaser is consistent with that of the continuum in IRAS 10173+0828. This means that the OH megamaser is a diffuse unsaturated maser which could amplify the diffuse 18 cm continuum emission with an amplification factor of order unity.展开更多
The XMM-Newton observations of H2O megamaser galaxy NGC 7479 are presented. Its smoothed X-ray image clearly shows spiral morphology, which matches well with its optical asymmetric spiral structure. One prominent sour...The XMM-Newton observations of H2O megamaser galaxy NGC 7479 are presented. Its smoothed X-ray image clearly shows spiral morphology, which matches well with its optical asymmetric spiral structure. One prominent source can be found at the tip of its northern spiral arm, which is much brighter than its nuclear X-ray source （about a 50% higher count rate）. For the nuclear source （a circular region with a radius of 20 ″）, the spectra show soft excess below 2 keV and a strong iron Kα emission line. The best fitting model includes a partially absorbed model for the hard continuum and one thermal plasma model for the soft scatter component. Both the high column density （NH - 6.88 × 10^23 cm^-2） and strong fluorescent iron line （with an equivalent width of - 1.5 keV） support the existence of one heavily obscured AGN. For the bright prominent source, its radial profile is consistent with that of a single point-like source. Its spectra are extracted from the circular region around its peak, with a radius of 20″ and 6″ respectively and both spectra show models for the ultra-luminous X-ray source no significant difference. Four alternative （ULXs） can reproduce the spectra well： an absorbed power law, thermal bremsstrahlung, multicolor blackbody disk plus another blackbody or power law. Further observations （e.g., the tremendous improvement in the spatial resolution of the Chandra X-ray observations） and studies are desirable for probing the nature of this prominent source. In addition, we also estimate the mass of its central engine to be 1.18 × 10^7 M⊙ and maser disk parameters： the disk radius of -0.7 pc and the dimensionless accretion rate （L2-10kev/LEdd） of 1.2 × 10^-4.展开更多
The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will make contributions to studies of Galactic and extragalactic masers. This telescope, with construction finished and now undergoing commissioning, has...The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will make contributions to studies of Galactic and extragalactic masers. This telescope, with construction finished and now undergoing commissioning, has an innovative design that leads to the highest sensitivity of any single dish radio telescope in the world. FAST's potential for OH megamaser research is discussed, including the sky density of masers detectable in surveys. The scientific impact expected from FAST maser studies is also discussed.展开更多
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 ...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∝MBH^3.6±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
文摘Many galaxies are thought to contain massive black holes, with masses in excess of ten million solar masses, at their centres and warped circumnuclear toruses. The best evidence comes from observing gas or masers rotating rapidly within a circumnuclear torus surrounding a central body. Here we report on the first MERLIN observations of line emission from the OH megamaser toward IRAS 10173+0828. The position of peak flux contours of the OH megamaser is consistent with that of the continuum in IRAS 10173+0828. This means that the OH megamaser is a diffuse unsaturated maser which could amplify the diffuse 18 cm continuum emission with an amplification factor of order unity.
基金supported by the National Natural Science Foundation of China (Grant No. 10633010)the Guangdong provincial Natural Science Foundation (8451009101001047)
文摘The XMM-Newton observations of H2O megamaser galaxy NGC 7479 are presented. Its smoothed X-ray image clearly shows spiral morphology, which matches well with its optical asymmetric spiral structure. One prominent source can be found at the tip of its northern spiral arm, which is much brighter than its nuclear X-ray source （about a 50% higher count rate）. For the nuclear source （a circular region with a radius of 20 ″）, the spectra show soft excess below 2 keV and a strong iron Kα emission line. The best fitting model includes a partially absorbed model for the hard continuum and one thermal plasma model for the soft scatter component. Both the high column density （NH - 6.88 × 10^23 cm^-2） and strong fluorescent iron line （with an equivalent width of - 1.5 keV） support the existence of one heavily obscured AGN. For the bright prominent source, its radial profile is consistent with that of a single point-like source. Its spectra are extracted from the circular region around its peak, with a radius of 20″ and 6″ respectively and both spectra show models for the ultra-luminous X-ray source no significant difference. Four alternative （ULXs） can reproduce the spectra well： an absorbed power law, thermal bremsstrahlung, multicolor blackbody disk plus another blackbody or power law. Further observations （e.g., the tremendous improvement in the spatial resolution of the Chandra X-ray observations） and studies are desirable for probing the nature of this prominent source. In addition, we also estimate the mass of its central engine to be 1.18 × 10^7 M⊙ and maser disk parameters： the disk radius of -0.7 pc and the dimensionless accretion rate （L2-10kev/LEdd） of 1.2 × 10^-4.
基金supported by the China Ministry of Science and Technology under the National Basic Research Program of China (973 program, 2012CB821800)the National Natural Science Foundation of China (Nos. 11473007, 11373038 and 11590782)supported by the Strategic Priority Research Program (No. XDB09000000) from the Chinese Academy of Sciences
文摘The Five-hundred-meter Aperture Spherical radio Telescope(FAST) will make contributions to studies of Galactic and extragalactic masers. This telescope, with construction finished and now undergoing commissioning, has an innovative design that leads to the highest sensitivity of any single dish radio telescope in the world. FAST's potential for OH megamaser research is discussed, including the sky density of masers detectable in surveys. The scientific impact expected from FAST maser studies is also discussed.
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∝MBH^3.6±0.4 which supports basically the theoretical prediction. The relation between the maser emission and X-ray emission is also confirmed.
