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A Measurement of the Hubble Constant by the Megamaser Cosmology Project

Published online by Cambridge University Press:  16 July 2018

James Braatz ,
James Condon ,
Christian Henkel ,
Jenny Greene ,
Fred Lo ,
Mark Reid ,
Dominic Pesce ,
Feng Gao ,
Violette Impellizzeri  and
Cheng-Yu Kuo
...Show all authors
James Braatz
Affiliation:
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
James Condon
Affiliation:
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
Christian Henkel
Affiliation:
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany Astronomy Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
Jenny Greene
Affiliation:
Department of Astrophysics, Princeton University, Princeton, NJ, 08544, USA
Fred Lo
Affiliation:
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
Mark Reid
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Dominic Pesce
Affiliation:
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904, USA
Feng Gao
Affiliation:
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 200030 Shanghai, China
Violette Impellizzeri
Affiliation:
Joint ALMA Office, Alonso de Cordova 3107, Vitacura, Santiago, Chile
Cheng-Yu Kuo
Affiliation:
Department of Physics, National Sun Yat-Sen University, No. 70, Lianhai Road, Gushan Dist., 804 Kaohsiung City, Taiwan, R.O.C.
Wei Zhao
Affiliation:
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 200030 Shanghai, China
Anca Constantin
Affiliation:
Department of Physics and Astronomy, James Madison University, Harrisonburg, VA 22807, USA
Lei Hao
Affiliation:
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 200030 Shanghai, China
Eugenia Litzinger
Affiliation:
Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Emil-Fischer-Str. 31, D-97074 Würzburg, Germany Dr. Remeis Sternwarte & ECAP, Universität Erlangen-Nürnberg, Sternwartstrasse 7, D-96049 Bamberg, Germany
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Abstract

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The Megamaser Cosmology Project (MCP) measures the Hubble Constant by determining geometric distances to circumnuclear 22 GHz H2O megamasers in galaxies at low redshift (z < 0.05) but well into the Hubble flow. In combination with the recent, exquisite observations of the Cosmic Microwave Background by WMAP and Planck, these measurements provide a direct test of the standard cosmological model and constrain the equation of state of dark energy. The MCP is a multi-year project that has recently completed observations and is currently working on final analysis. Based on distance measurements to the first four published megamasers in the sample, the MCP currently determines H0 = 69.3 ± 4.2 km s−1 Mpc−1. The project is finalizing analysis for five additional galaxies. When complete, we expect to achieve a ~4% measurement. Given the tension between the Planck prediction of H0 in the context of the standard cosmological model and astrophysical measurements based on standard candles, the MCP provides a critical and independent geometric measurement that does not rely on external calibrations or a distance ladder.

Keywords

masersdistance scale
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S336: Astrophysical Masers: Unlocking the Mysteries of the Universe , September 2017 , pp. 86 - 91
Copyright
Copyright © International Astronomical Union 2018 

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