A geometric distance to CGCG 074-064
Abstract
As part of the Megamaser Cosmology Project (MCP), we have made a direct measurement of the angular-diameter distance to the megamaser galaxy CGCG 074-064. We have conducted a series of high-sensitivity very long baseline interferometric observations, which reveal that the masers reside in a thin, edge-on accretion disk exhibiting Keplerian rotation at orbital radii <0.5 pc from the central supermassive black hole. Over two years of single-dish spectral monitoring, we have determined that the maser features near the systemic velocity of the galaxy display nearly uniform velocity drifts of ~4.3 km/s/yr, implying that they originate from a thin annulus in the disk. Combining these datasets, we have fit a 3D warped-disk model to the data and derived a distance and corresponding Hubble constant measurement for this galaxy. With an uncertainty of <9%, our distance measurement to CGCG 074-064 is the most precise yet obtained by the MCP.
- Publication:
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American Astronomical Society Meeting Abstracts #231
- Pub Date:
- January 2018
- Bibcode:
- 2018AAS...23112303P