Several thin, Keplerian, sub-parsec megamaser disks have been discovered in the nuclei of active galaxies and used to precisely determine the mass of their host black holes. We show that there is an empirical linear correlation between the disk radius and the black hole mass. We demonstrate that such disks are naturally formed by the partial capture of molecular clouds passing through the galactic nucleus and temporarily engulfing the central supermassive black hole. Imperfect cancellation of the angular momenta of the cloud material colliding after passing on opposite sides of the hole leads to the formation of a compact disk. The radial extent of the disk is determined by the efficiency of this process and the Bondi-Hoyle capture radius of the black hole, and naturally produces the empirical linear correlation of the radial extent of the maser distribution with black hole mass. The disk has sufficient column density to allow X-ray irradiation from the central source to generate physical and chemical conditions conducive to the formation of 22 GHz H2O masers. For initial cloud column densities less than ~10^{23.5} cm^-2 the disk is non-self gravitating, consistent with the ordered kinematics of the edge-on megamaser disks; for higher cloud columns the disk would fragment and produce a compact stellar disk similar to that observed around Sgr A* at the galactic centre.
Several examples of thin, Keplerian, sub-parsec megamaser disks have been discovered in the nuclei of active galaxies and used to precisely determine the mass of their host black holes. We show that there is an empirical linear correlation between the disk radius and black hole mass and that such disks are naturally formed as molecular clouds pass through the galactic nucleus and temporarily engulf the central supermassive black hole. For initial cloud column densities below about 10^{23.5} cm^{-2} the disk is non-self gravitating, but for higher cloud columns the disk would fragment and produ…
In this work we perform a Bayesian statistical fit to estimate the mass-to-distance ratio and the recessional redshift of 10 different black holes hosted at the centre of active galactic nuclei, namely the galaxies NGC 5765b, NGC 6323, UGC 3789, CGCG 074-064, ESO 558-G009, NGC 2960, NGC 6264, NGC 4388, J0437+2456 and NGC 2273. Our general relativistic method makes use of the positions in the sky and frequency shift observations of water megamasers circularly orbiting the central black hole on their accretion disks. This approach also allows us to quantify the gravitational redshift which is no…
Luminous extragalactic masers are traditionally referred to as the `megamasers'. Those produced by water molecules are associated with accretion disks, radio jets, or outflows in the nuclear regions of active galactic nuclei (AGN). The majority of OH maser sources are instead driven by intense star formation in ultra-luminous infrared galaxies, although in a few cases the OH maser emission traces rotating (toroidal or disk) structures around the nuclear engines of AGN. Thus, detailed maser studies provide a fundamental contribution to our knowledge of the main nuclear components of AGN, consti…
As part of the Megamaser Cosmology Project (MCP), here we present a new geometric distance measurement to the megamaser galaxy NGC 5765b. Through a series of VLBI observations, we have confirmed the water masers trace a thin, sub-parsec Keplerian disk around the nucleus, implying an enclosed mass of 4.55 $\pm$ 0.40 $\times~10^{7}M_\odot$. Meanwhile, from single dish monitoring of the maser spectra over two years, we measured the secular drifts of maser features near the systemic velocity of the galaxy with rates between 0.5 and 1.2 km s$^{-1}$ yr$^{-1}$. Fitting a warped, thin disk model to th…
Observations of H$_2$O masers from circumnuclear disks in active galaxies for the Megamaser Cosmology Project allow accurate measurement of the mass of supermassive black holes (BH) in these galaxies. We present the Very Long Baseline Interferometry (VLBI) images and kinematics of water maser emission in six active galaxies: NGC~1194, NGC~2273, NGC~2960 (Mrk~1419), NGC~4388, NGC~6264 and NGC~6323. We use the Keplerian rotation curves of these six megamaser galaxies, plus a seventh previously published, to determine accurate enclosed masses within the central $\sim0.3$ pc of these galaxies, sma…
Population search for dark matter spikes in megamaser rotation curves
Kavli Institute for Astrophysics and Department of Physics, Massachusetts Institute of Technology（麻省理工学院卡弗里天体物理研究所与物理系）；Harvard Laboratory for Particle Physics and Cosmology and Department of Physics, Harvard University（哈佛大学粒子物理与宇宙学实验室与物理系）
Black hole - galaxy scaling relations provide information about the coevolution of supermassive black holes and their host galaxies. We compare the black hole mass - circular velocity (MBH - Vc) relation with the black hole mass - bulge stellar velocity dispersion (MBH - sigma) relation, to see whether the scaling relations can passively emerge from a large number of mergers, or require a physical mechanism, such as feedback from an active nucleus. We present VLA H I observations of five galaxies, including three water megamaser galaxies, to measure the circular velocity. Using twenty-two gala…
High-frequency water megamasers as precision probes of black holes, galaxies and cosmology: A case for a next-generation sub-mm/mm interferometer
New York University Abu Dhabi（阿布扎比纽约大学）；ASTRON, Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；Black Hole Initiative, Harvard University（哈佛大学黑洞倡议项目）；European Southern Observatory (ESO)（欧洲南方天文台）；University of Geneva（日内瓦大学）；National Sun Yat-Sen University（国立中山大学）；Bucknell University（巴克内尔大学）；Toyo University（东洋大学）；Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及天文物理研究所）；National Radio Astronomy Observatory（美国国家射电天文台）
Here we present observational evidence that the broad emission line region (BELR) of active galactic nuclei (AGN) generally has an outer boundary. This was already clear for sources with an obvious transition between the broad and narrow components of their emission lines. We show that the narrow component of the higher-order Paschen lines is absent in all sources, revealing a broad emission line profile with a broad, flat top. This indicates that the BELR is kinematically separate from the narrow emission line region. We use the virial theorem to estimate the BELR outer radius from the flat t…
Local samples of quiescent galaxies with dynamically measured black hole masses (Mbh) may suffer from an angular resolution-related selection effect, which could bias the observed scaling relations between Mbh and host galaxy properties away from the intrinsic relations. In particular, previous work has shown that the observed Mbh-Mstar (stellar mass) relation is more strongly biased than the Mbh-sigma (velocity dispersion) relation. Local samples of active galactic nuclei (AGN) do not suffer from this selection effect, as in these samples Mbh is estimated from megamasers and/or reverberation …
(Abridged) We present a comprehensive analysis of the spatially resolved stellar population properties of 26 early-type dwarf (dE) galaxies in the Virgo cluster. Using Lick/IDS absorption line indices we derive simple stellar population(SSP)-equivalent age, metallicity and [$α$/Fe] abundance ratio. In particular, we focus on the comparison of the stellar populations between the central nucleus and the surrounding galactic main body. The stellar populations of the nuclei are, for most dEs, significantly younger than those of the respective galactic main bodies, with an average difference of 3.5…
Black hole masses for samples of active galactic nuclei (AGN) are currently estimated from single-epoch optical spectra. In particular, the size of the broad-line emitting region needed to compute the black hole mass is derived from the optical or ultraviolet continuum luminosity. Here we consider the relationship between the broad-line region size, R, and the near-infrared (near-IR) AGN continuum luminosity, L, as the near-IR continuum suffers less dust extinction than at shorter wavelengths and the prospects for separating the AGN continuum from host-galaxy starlight are better in the near-I…
The Radius-Luminosity Relationship for Active Galactic Nuclei with Hierarchical Bayesian Reverberation Mapping
University of Queensland（昆士兰大学）；Macquarie University（麦考瑞大学）；Astrophysics and Space Technologies Research Centre, Macquarie University（麦考瑞大学天体物理与空间技术中心）；The Ohio State University（俄亥俄州立大学）；Kavli Institute for Particle Astrophysics and Cosmology, Stanford University（斯坦福大学卡弗里粒子天体物理学与宇宙学研究所）；Australian National University（澳大利亚国立大学）；Sydney Institute for Astronomy, School of Physics, A28, University of Sydney（悉尼大学A28物理学院悉尼天文研究所）
A sublimation process governs the innermost region of the dusty torus of active galactic nuclei. However, the observed inner radius of the torus is systematically smaller than the expected radius by a factor of ~ 1/3. We show that the anisotropy of the emission from accretion disks resolves this conflict naturally and quantitatively. An accretion disk emits lesser radiation in the direction closer to its equatorial plane (i.e., to the torus). We find that the anisotropy makes the torus inner region closer to the central black hole and concave. Moreover, the innermost edge of the torus may conn…
Standardizing reverberation-mapped H$α$ and H$β$ active galactic nuclei using radius--luminosity relations involving monochromatic and broad H$α$ luminosities
Standardizing a larger, higher-quality, homogeneous sample of reverberation-mapped H$β$ active galactic nuclei using the broad-line region radius-luminosity relation
We present an updated and revised analysis of the relationship between the Hbeta broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of 9 new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new …
Standardizing reverberation-mapped H$β$ active galactic nuclei using time-averaged radius$-$luminosity relations with 5100\,Å\,, broad H$β$, and narrow \OIII\ luminosities
