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RISS 인기검색어
- 검색키워드
- 저자 : Impellizzeri, C. M. V. (검색결과 4 건)
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Enhancing the H<sub>2</sub>O Megamaser Detection Rate Using Optical and Mid-infrared Photometry
Kuo, C. Y.,Constantin, A.,Braatz, J. A.,Chung, H. H.,Witherspoon, C. A.,Pesce, D.,Impellizzeri, C. M. V.,Gao, F.,Hao, Lei,Woo, J.-H.,Zaw, Ingyin American Astronomical Society 2018 The Astrophysical journal Vol.860 No.2
<P>Water megamasers from circumnuclear disks in galaxy centers provide the most accurate measurements of supermassive black hole masses and uniquely probe the subparsec accretion processes. At the same time, these systems offer independent crucial constraints of the Hubble constant in the nearby universe, and thus, the arguably best single constraint on the nature of dark energy. The chances of finding these golden standards are, however, abysmally low, at less than or similar to 3% overall for any level of water maser emission detected at 22 GHz and less than or similar to 1% for those exhibiting disk-like configuration. We provide here a thorough summary of the current state of detection of water megamaser disks along with a novel investigation of the likelihood of increasing their detection rates based on a multivariate parameter analysis of the optical and mid-infrared (mid-IR) photometric properties of the largest database of galaxies surveyed for 22 GHz emission. We find that galaxies with water megamaser emission tend to be associated with strong emission in all Wide-field Infrared Survey Explorer mid-IR wavelengths, with the strongest enhancement in the W4 band, at 22 mu m, as well as with previously proposed and newly found indicators of active galactic nucleus strength in the mid-IR, such as red W1 - W2 and W1 - W4 colors, and the integrated mid-IR luminosity of the host galaxy. These trends offer a potential boost of the megamaser detection rates to 6%-15%, or a factor of 2-8 relative to the current rates, depending on the chosen sample selection criteria, while fostering real chances for discovering. 20 new megamaser disks.</P>
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THE MEGAMASER COSMOLOGY PROJECT. IX. BLACK HOLE MASSES FOR THREE MASER GALAXIES
Gao, F.,Braatz, J. A.,Reid, M. J.,Condon, J. J.,Greene, J. E.,Henkel, C.,Impellizzeri, C. M. V.,Lo, K. Y.,Kuo, C. Y.,Pesce, D. W.,Wagner, J.,Zhao, W. American Astronomical Society 2017 The Astrophysical journal Vol.834 No.1
<P>As part of the Megamaser Cosmology Project, 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 +/- 0.3) x 10(6)M(Theta) for J0437+2456, (1.7 +/- 0.1) x 10(7)M(Theta) for ESO 558-G009, and (1.1 +/- 0.2) x 10(7)M(Theta) for NGC 5495. In the other two galaxies, Mrk 1029 and NGC 1320, the geometry and dynamics are more complicated and preclude robust black hole mass estimates. Including our new results, we compiled a list of 15 VLBI-confirmed disk maser galaxies with robust SMBH mass measurements. With this sample, we confirm the empirical relation of R-out proportional to 0.3M(SMBH) reported in Wardle & Yusef-Zadeh. We also find a tentative correlation between maser disk outer radii and Wide-Field Infrared Survey Explorer luminosity. We find no correlations of maser disk size with X-ray 2-10 keV luminosity or [O III] luminosity.</P>
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THE 2014 ALMA LONG BASELINE CAMPAIGN: OBSERVATIONS OF ASTEROID 3 JUNO AT 60 KILOMETER RESOLUTION
Hunter, T. R.,Kneissl, R.,Moullet, A.,Brogan, C. L.,Fomalont, E. B.,Vlahakis, C.,Asaki, Y.,Barkats, D.,Dent, W. R. F.,Hills, R. E.,Hirota, A.,Hodge, J. A.,Impellizzeri, C. M. V.,Liuzzo, E.,Lucas, R.,M IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.808 No.1
<P>We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum images of the asteroid 3 Juno obtained with an angular resolution of 0 ''.042 (60 km at 1.97 AU). The data were obtained over a single 4.4 hr interval, which covers 60% of the 7.2 hr rotation period, approximately centered on local transit. A sequence of 10 consecutive images reveals continuous changes in the asteroid's profile and apparent shape, in good agreement with the sky projection of the three-dimensional model of the Database of Asteroid Models from Inversion Techniques. We measure a geometric mean diameter of 259 +/- 4 km, in good agreement with past estimates from a variety of techniques and wavelengths. Due to the viewing angle and inclination of the rotational pole, the southern hemisphere dominates all of the images. The median peak brightness temperature is 215 +/- 13 K, while the median over the whole surface is 197 +/- 15 K. With the unprecedented resolution of ALMA, we find that the brightness temperature varies across the surface with higher values correlated to the subsolar point and afternoon areas and lower values beyond the evening terminator. The dominance of the subsolar point is accentuated in the final four images, suggesting a reduction in the thermal inertia of the regolith at the corresponding longitudes, which are possibly correlated to the location of the putative large impact crater. These results demonstrate ALMA's potential to resolve thermal emission from the surface of main belt asteroids and to measure accurately their position, geometric shape, rotational period, and soil characteristics.</P>
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Vlahakis, C.,Hunter, T. R.,Hodge, J. A.,Pé,rez, L. M.,Andreani, P.,Brogan, C. L.,Cox, P.,Martin, S.,Zwaan, M.,Matsushita, S.,Dent, W. R. F.,Impellizzeri, C. M. V.,Fomalont, E. B.,Asaki, Y.,Barka IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.808 No.1
<P>We present initial results of very high resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the z = 3.042 gravitationally lensed submillimeter galaxy HATLAS J090311.6+003906 (SDP. 81). These observations were carried out using a very extended configuration as part of Science Verification for the 2014 ALMA Long Baseline Campaign, with baselines of up to similar to 15 km. We present continuum imaging at 151, 236, and 290 GHz at unprecedented angular resolutions as fine as 23 mas, corresponding to an unmagnified spatial scale of similar to 180 pc at z = 3.042. The ALMA images clearly show two main gravitational arc components of an Einstein ring, with emission tracing a radius of similar to 1 ''.5. We also present imaging of CO J = 10 - 9, J = 8 - 7, and J = 5 - 4 and H2O (202-111) line emission. The CO emission, at an angular resolution of similar to 170 mas, is found to broadly trace the gravitational arc structures but with differing morphologies between the CO transitions and compared to the dust continuum. Our detection of H2O line emission, using only the shortest baselines, provides the most resolved detection to date of thermal H2O emission in an extragalactic source. The ALMA continuum and spectral line fluxes are consistent with previous Plateau de Bure Interferometer and Submillimeter Array observations despite the impressive increase in angular resolution. Finally, we detect weak unresolved continuum emission from a position that is spatially coincident with the center of the lens, with a spectral index that is consistent with emission from the core of the foreground lensing galaxy.</P>
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