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18 OTTOBRE 2016 ore 11:00
Oggi Astro Chiacchiere!
Exploring Supermassive Black Holes and the Hubble Constant with Megamasers
Jim Braatz (NRAO, USA)
Figure: The left panel shows a map of the maser distribution in the nucleus of NGC5765b, while the right panel shows a position-velocity diagram revealing an exquisite Keplerian rotation profile.
Abstract
Water vapor megamasers provide the only direct means for mapping sub-parsec accretion disks in active galactic nuclei. In the best cases they trace exquisite Keplerian rotation profiles and provide the gold standard measurements of masses of SMBH. In a few galaxies, the masers have been used to determine geometric distances to the host galaxies, thereby providing a direct, one-step measurement of the Hubble Constant, independent of standard candles. In light of the discrepancy between the Planck prediction of H0 based on CMB measurements and the direct measurement of H0 from standard candles, an independent and geometric measurement is particularly valuable. I will discuss the Megamaser Cosmology Project, which is pursuing these goals of studying SMBH and the Hubble Constant. If the technique can be pushed in the future to achieve even higher accuracy, it can also lead to a constraint on neutrino mass.
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Oggi Astro Chiacchiere! è un incontro informale, a cadenza bisettimanale, tra il personale dell'Osservatorio Astronomico di Cagliari (staff, postdoc e studenti), che ha lo scopo di discutere argomenti di carattere prevalentemente scientifico, tecnologico e informatico. L'incontro si tiene solitamente il Martedì, alle ore 11, nell'Auditorium dell'Osservatorio Astronomico di Cagliari.
Abstract
Water vapor megamasers provide the only direct means for mapping sub-parsec accretion disks in active galactic nuclei. In the best cases they trace exquisite Keplerian rotation profiles and provide the gold standard measurements of masses of SMBH. In a few galaxies, the masers have been used to determine geometric distances to the host galaxies, thereby providing a direct, one-step measurement of the Hubble Constant, independent of standard candles. In light of the discrepancy between the Planck prediction of H0 based on CMB measurements and the direct measurement of H0 from standard candles, an independent and geometric measurement is particularly valuable. I will discuss the Megamaser Cosmology Project, which is pursuing these goals of studying SMBH and the Hubble Constant. If the technique can be pushed in the future to achieve even higher accuracy, it can also lead to a constraint on neutrino mass.
---------------------------------------------------------------------------------------------------------
Oggi Astro Chiacchiere! è un incontro informale, a cadenza bisettimanale, tra il personale dell'Osservatorio Astronomico di Cagliari (staff, postdoc e studenti), che ha lo scopo di discutere argomenti di carattere prevalentemente scientifico, tecnologico e informatico. L'incontro si tiene solitamente il Martedì, alle ore 11, nell'Auditorium dell'Osservatorio Astronomico di Cagliari.
Per informazioni e/o contributi contattare pcastang@oa-cagliari.inaf.it