We present high resolution (sub-mas) VLBI maps of nuclear H2O megamasers for seven galaxies. In UGC6093, the well-aligned systemic masers and high-velocity masers originate in an edge-on, flat disk and we determine the mass of the central SMBH to be M_SMBH = 2.58*10^7Msun(+-7%). For J1346+5228, the distribution of masers is consistent with a disk, but the faint high-velocity masers are only marginally detected, and we constrain the mass of the SMBH to be in the range 1.5-2.0*10^7Msun. The origin of the masers in Mrk1210 is less clear, as the systemic and high-velocity masers are misaligned and show a disorganized velocity structure. We present one possible model in which the masers originate in a tilted, warped disk, but we do not rule out the possibility of other explanations including outflow masers. In NGC6926, we detect a set of redshifted masers, clustered within a pc of each other, and a single blueshifted maser about 4.4pc away, an offset that would be unusually large for a maser disk system. Nevertheless, if it is a disk system, we estimate the enclosed mass to be M_SMBH<4.8*10^7 Msun . For NGC5793, we detect redshifted masers spaced about 1.4pc from a clustered set of blueshifted features. The orientation of the structure supports a disk scenario as suggested by Hagiwara et al.(2001). We estimate the enclosed mass to be M SMBH<1.3*10^7 Msun. For NGC2824 and J0350-0127, the masers may be associated with pc or sub-pc scale jets or outflows.
In combination with observations of the Cosmic Microwave Background, a measurement of the Hubble Constant provides a direct test of the standard $Λ$CDM cosmological model and a powerful constraint on the equation of state of dark energy. Observations of circumnuclear water vapor megamasers at 22 GHz in nearby active galaxies can be used to measure their distances, geometrically, and thereby provide a direct, one step measurement of the Hubble Constant. The measurement is independent of distance ladders and standard candles. With present-day instrumentation, the Megamaser Cosmology Project is e…
H$_2$O megamasers residing in the accretion disks of active galactic nuclei (AGN) exhibit Keplerian rotation about the central supermassive black hole (SMBH). Such disk maser systems are excellent tools for diagnosing the kinematic status of the SMBH, and they currently provide the only direct and unambiguous measure of SMBH velocities outside of the Milky Way. We have measured the galaxy recession velocities for a sample of 10 maser disk systems using a combination of spatially resolved HI disk modeling, spatially integrated HI profile fitting, and optical spectral line and continuum fitting.…
We present observations of the H2O megamasers in the accretion disk of NGC 6323. By combining interferometric and spectral monitoring data, we estimate H$_{0} = 73^{+26}_{-22}$ km/s/Mpc, where the low strength of the systemic masers (<15 mJy) limits the accuracy of this estimate. The methods developed here for dealing with weak maser emission provide guidance for observations of similar sources, until significant increases in radio telescope sensitivity, such as anticipated from the next generation Very Large Array, are realized.
In Papers I and II from the Megamaser Cosmology Project (MCP), we reported initial observations of water masers in an accretion disk of a supermassive black hole at the center of the galaxy UGC 3789, which gave an angular-diameter distance to the galaxy and an estimate of Ho with 16% uncertainty. We have since conducted more VLBI observations of the spatial-velocity structure of these water masers, as well as continued monitoring of its spectrum to better measure maser accelerations. These more extensive observations, combined with improved modeling of the masers in the accretion disk of the c…
We use single-dish radio spectra of known 22 GHz H$_2$O megamasers, primarily gathered from the large dataset observed by the Megamaser Cosmology Project, to identify Keplerian accretion disks and to investigate several aspects of the disk physics. We test a mechanism for maser excitation proposed by Maoz & McKee (1998), whereby population inversion arises in gas behind spiral shocks traveling through the disk. Though the flux of redshifted features is larger on average than that of blueshifted features, in support of the model, the high-velocity features show none of the predicted systematic …
We present a measurement of the Hubble constant made using geometric distance measurements to megamaser-hosting galaxies. We have applied an improved approach for fitting maser data and obtained better distance estimates for four galaxies previously published by the Megamaser Cosmology Project: UGC 3789, NGC 6264, NGC 6323, and NGC 5765b. Combining these updated distance measurements with those for the maser galaxies CGCG 074-064 and NGC 4258, and assuming a fixed velocity uncertainty of 250 km s$^{-1}$ associated with peculiar motions, we constrain the Hubble constant to be $H_0 = 73.9 \pm 3.…
WISDOM project -- XVIII. Molecular gas distributions and kinematics of three megamaser galaxies
University of Oxford（牛津大学）；Yonsei University（延世大学）；Universität Hamburg（汉堡大学）；Cardiff University（卡迪夫大学）；Princeton University（普林斯顿大学）；SOKENDAI（综合研究大学院大学）
As part of the Megamaser Cosmology Project (MCP), we present VLBI maps of nuclear water masers toward five galaxies. The masers originate in sub-parsec circumnuclear disks. For three of the galaxies, we fit Keplerian rotation curves to estimate their supermassive black hole (SMBH) masses, and determine (2.9 $\pm$ 0.3) $\times~10^{6}M_\odot$ for J0437+2456, (1.7 $\pm$ 0.1) $\times~10^{7}M_\odot$ for ESO 558$-$G009, and (1.1 $\pm$ 0.2) $\times~10^{7}M_\odot$ for NGC 5495. In the other two galaxies, Mrk 1029 and NGC 1320, the geometry and dynamics are more complicated and preclude robust black ho…
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…
Using HST, we identify circumnuclear ($100$-$500$ pc scale) structures in nine new H$_2$O megamaser host galaxies to understand the flow of matter from kpc-scale galactic structures down to the supermassive black holes (SMBHs) at galactic centers. We double the sample analyzed in a similar way by Greene et al. (2013) and consider the properties of the combined sample of 18 sources. We find that disk-like structure is virtually ubiquitous when we can resolve $<200$ pc scales, in support of the notion that non-axisymmetries on these scales are a necessary condition for SMBH fueling. We perform a…
We present VLBI images and kinematics of water maser emission in three active galaxies: NGC 5728, Mrk 1, and IRAS 08452-0011. IRAS 08452-0011 is a triple-peaked H2O megamaser, consistent with a Keplerian rotating disk, indicating a black hole mass of (3.3+/-0.2)x10^7 M_sun. NGC 5728 and Mrk 1 display double-peaked spectra and VLBI imaging reveal complicated gas kinematics, which do not allow for a robust determination of black hole mass. The two systems are either gas disks perturbed by AGN winds or part of outflows. We find that disturbed morphology and kinematics are a ubiquitous feature of …
As part of the survey component of the Megamaser Cosmology Project, we have discovered a disk megamaser system in the galaxy CGCG 074-064. Using the GBT and the VLA, we have obtained spectral monitoring observations of this maser system at a monthly cadence over the course of two years. We find that the systemic maser features display line-of-sight accelerations of ~4.4 km s$^{-1}$ yr$^{-1}$ that are nearly constant with velocity, while the high-velocity maser features show accelerations that are consistent with zero. We have also used the HSA to make a high-sensitivity VLBI map of the maser s…
Megamaser disks provide the most precise and accurate extragalactic supermassive black hole masses. Here we describe a search for megamasers in nearby galaxies using the Green Bank Telescope (GBT). We focus on galaxies where we believe that we can resolve the gravitational sphere of influence of the black hole and derive a stellar or gas dynamical measurement with optical or NIR observations. Since there are only a handful of super massive black holes (SMBH) that have direct black hole mass measurements from more than one method, even a single galaxy with a megamaser disk and a stellar dynamic…
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）
We present the results from an observing campaign to confirm the peculiar motion of the supermassive black hole (SMBH) in J0437+2456 first reported in Pesce et al. (2018). Deep observations with the Arecibo Observatory have yielded a detection of neutral hydrogen (HI) emission, from which we measure a recession velocity of 4910 km s$^{-1}$ for the galaxy as a whole. We have also obtained near-infrared integral field spectroscopic observations of the galactic nucleus with the Gemini North telescope, yielding spatially resolved stellar and gas kinematics with a central velocity at the innermost …
The relation between the mass of supermassive black holes located in the center of the host galaxies and the kinetic energy of random motions of the corresponding bulges can be reinterpreted as an age-temperature diagram for galaxies. This relation fits the experimental data better than the M_bh-M_G, M_bh-L_G, and M_bh-sigma laws. The validity of this statement has been confirmed by using three samples extracted from different catalogues of galaxies. In the framework of the LambdaCDM cosmology our relation has been compared with the predictions of two galaxy formation models based on the Mille…
IC 485:a new candidate disk-maser galaxy at $\sim$100 Mpc distance. Milliarcsecond resolution study of the galaxy nucleus and of the $H_{2}O$ megamaser
As part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM), we present a measurement of the mass of the supermassive black hole (SMBH) in the nearby early-type galaxy NGC 0383 (radio source 3C 031). This measurement is based on Atacama Large Millimeter/sub-milimeter Array (ALMA) cycle 4 and 5 observations of the 12CO(2-1) emission line with a spatial resolution of 58x32pc2 (0."18x0."1). This resolution, combined with a channel width of 10 km/s, allows us to well resolve the radius of the black hole sphere of influence (measured as R_SOI = 316pc = 0."98), where we detect a cle…
The co-evolution of galaxies and the supermassive black holes (SMBHs) at their centers via hierarchical galaxy mergers is a key prediction of $Λ$CDM cosmology. As gas and dust are funneled to the SMBHs during the merger, the SMBHs light up as active galactic nuclei (AGNs). In some cases, a merger of two galaxies can encounter a third galaxy, leading to a triple merger, which would manifest as a triple AGN if all three SMBHs are simultaneously accreting. Using high-spatial resolution X-ray, near-IR, and optical spectroscopic diagnostics, we report here a compelling case of an AGN triplet with m…
The largest observed supermassive black holes (SMBHs) have a mass of M_BH ~ 10^{10} M_sun, nearly independent of redshift, from the local (z~0) to the early (z>6) Universe. We suggest that the growth of SMBHs above a few 10^{10} M_sun is prevented by small-scale accretion physics, independent of the properties of their host galaxies or of cosmology. Growing more massive BHs requires a gas supply rate from galactic scales onto a nuclear region as high as >10^3 M_sun/yr. At such a high accretion rate, most of the gas converts to stars at large radii (~10-100 pc), well before reaching the BH. We …
