maser astrometry with vlbi and galactic structure
DESCRIPTION
Maser Astrometry with VLBI and Galactic Structure. Mareki Honma Mizusawa VLBI Observatory, NAOJ. Milky Way & VERA Ogasawara station. Back to 115 years ago …. Carlo Forte. International Latitude Observatory (ILO), founded in 1899. ILO Mizusawa: now Mizusawa VLBI Observatory - PowerPoint PPT PresentationTRANSCRIPT
Maser Astrometry with VLBIand Galactic Structure
Mareki Honma
Mizusawa VLBI Observatory, NAOJ
Milky Way & VERA Ogasawara station
Back to 115 years ago …
ILO Mizusawa: now Mizusawa VLBI Observatory
ILO Carlo Forte: now Cagliari Astron. Observatory
Mizusawa
Carlo Forte
International Latitude Observatory (ILO), founded in 1899
both working on radio/VLBI
Galaxy-scale maser astrometry
GC distance D= 8 kpc, π= 125 μasrequires 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
Sun Galaxy Center
Parallax
Arrays• VERA, VLBA, EVN. All in the Northern
hemisphere.
• LBA, only one in the South
Astrometry examples• Chibueze+(2014) NGC6334I(N) D ~ 1.27 kpc
• Min+(2014) R Aqr D ~ 218 pc
EVN astrometry
Rygl+(2012), astrometry of masers in Cygnus X complex
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
Galactic structure II: Honma+(2012)• 52 sources from VERA/VLBA/EVN
R0=8.05 +/- 0.45 kpc, Θ0=238 +/- 14 km/s
III. Reid+(2014)
• 103 sources
R0 = 8.34+/-0.16 kpc
Θ0 = 240 +/- 8 km/s
Galactic constants
Reid+(2009)
Honma+(2012)
Reid+(2014)
Nsrc 18 52 103
R0 (kpc) 8.4(+/- 0.6)
8.05(+/- 0.45)
8.34(+/- 0.16)
Θ0
(km/s)247
(+/- 16)238
(+/- 14)240
(+/- 8)
Galactic constants are already measured at a few percent level !
Most updated data as of Oct 2014
114 sources from VLBA/VERA/EVN
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 ?
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 (!?)
Concluding remarks
• VLBI can certainly do 10-uas level astrometry.
• Parallax and proper motions are obtained for more than 100 source.
• VLBI astrometry readily provides excellent results on the Galactic structure and beyond.
East Asian VLBI
Array extension to East Asia regions
Better sensitivity, better imaging capability -> better astrometry
SHAO 65m
KVN 21m x3
202x ~ ?
Mizusawa
Carlo Forte
1899~
Corresponding to ~7% SKA in collecting area !
Thank you for attention!
And let’s keep collaboration for next 100 years !