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Maser Astrometry with VLBI and Galactic Structure

Explore the evolution of astrometry with VLBI technology for Galactic structure analysis from 115 years ago to the present, showcasing advancements in radio/VLBI, parallax measurements, and Milky Way studies. Discover how VLBI arrays VERA, VLBA, EVN, and LBA contribute to astrometry examples like NGC6334I(N) and R.Aqr. Witness the impacts of VLBI astrometry on Galactic constants, spiral arm tracing, and broader interdisciplinary fields such as dark matter flux, gravitational wave studies, and potential mass extinctions. Join the discussion on East Asian VLBI expansions with KVN arrays and SHAO's significant collecting area growth since 1899.

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Maser Astrometry with VLBI and Galactic Structure

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  1. Maser Astrometry with VLBIand Galactic Structure Mareki Honma Mizusawa VLBI Observatory, NAOJ Milky Way & VERA Ogasawara station

  2. Back to 115 years ago … Carlo Forte International Latitude Observatory (ILO), founded in 1899 ILO Mizusawa: now Mizusawa VLBI Observatory ILO Carlo Forte: now Cagliari Astron. Observatory both working on radio/VLBI Mizusawa

  3. Sun Galaxy Center Galaxy-scale maser astrometry Parallax GC distance D=8 kpc, π=125 μas requires 10-μas accuracy Galaxy scale astrometry : frontier in 21st century (e.g. GAIA) • Relative VLBI astrometry certainly can measure this δx ~ θ sep c δt / B δx ~ 10 μas for reasonable parameters

  4. Arrays • VERA, VLBA, EVN. All in the Northern hemisphere. • LBA, only one in the South

  5. Astrometry examples • Chibueze+(2014) NGC6334I(N) D ~ 1.27 kpc • Min+(2014) R Aqr D ~ 218 pc

  6. EVN astrometry Rygl+(2012), astrometry of masers in Cygnus X complex

  7. Galactic structure • Reid+(2009): Early results based on 18 sources • R0 = 8.4 +/- 0.6 kpc, Θ0 = 247 +/- 16 km/s • 489 citations as of Oct 2014, good demonstration of impacts of VLBI astrometry in this field

  8. Galactic structure II: Honma+(2012) • 52 sources from VERA/VLBA/EVN R0=8.05 +/- 0.45 kpc, Θ0=238 +/- 14 km/s

  9. III. Reid+(2014) • 103 sources R0 = 8.34+/-0.16 kpc Θ0 = 240 +/- 8 km/s

  10. Galactic constants Galactic constants are already measured at a few percent level !

  11. Most updated data as of Oct 2014 114 sources from VLBA/VERA/EVN

  12. Tracing spiral arms • Non-circular systematic motion has been detected • Slow-rotation along the Perseus arm Useful for testing the spiral arm scenario --- density wave or material wave ?

  13. Broader impacts beyond astronomy • Direct Dark Matter search Galactic rotation is the key to know the flux of dark matter particles on Earth. • Gravitational wave Until recently the largest uncertainty in the Hulse-Taylor pulsar was Galactic acceleration. • Mass extinction on the Earth !!?? There is a claim that Sun’s spiral-arm passage could have caused the global climate change (!?)

  14. Concluding remarks • VLBI can certainly do 10-uas levelastrometry. • Parallax and proper motions are obtained for more than 100 source. • VLBI astrometry readily provides excellent results on the Galactic structure and beyond.

  15. East Asian VLBI KVN 21m x3 Array extension to East Asia regions Better sensitivity, better imaging capability -> better astrometry SHAO 65m

  16. 1899~ 202x ~ ? Carlo Forte Mizusawa Corresponding to ~7% SKA in collecting area !

  17. Thank you for attention!And let’s keep collaboration for next 100 years !

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