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Associating Sites of Methanol Masers at 6.7 GHz in Onsala 1

2009 East Asia VLBI Workshop, Seoul, Korea 2009, 3, 18-20. Associating Sites of Methanol Masers at 6.7 GHz in Onsala 1. Sugiyama, Koichiro 杉山 孝一郎 스기야마 코이치로 (Yamaguchi University). Contents. 6.7 GHz methanol maser Associating sites : disk or outflow ? Target : Onsala 1 Results

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Associating Sites of Methanol Masers at 6.7 GHz in Onsala 1

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  1. 2009 East Asia VLBI Workshop, Seoul, Korea 2009, 3, 18-20 Associating Sites of Methanol Masers at 6.7 GHz in Onsala 1 Sugiyama, Koichiro 杉山 孝一郎 스기야마 코이치로 (Yamaguchi University)

  2. Contents • 6.7 GHz methanol maser • Associating sites : disk or outflow ? • Target : Onsala 1 • Results • Superpose on other masers, lines, continuum • Internal proper motions • Summary

  3. 6.7 GHz methanol maser • For study of massive star-forming regions (MSFRs) • associated with only MSFRs • tracing early evolutionary phase ： ～104 yr • very strong and bright（second to the water masers） • compact ： several AU • For astrometry • many sources ： ～900 • long lifetime and stable ： > 4 yr • small effect by water vapor • Potentially issue • Associating sites ： Disk or Outflow ?

  4. Associating sites : disk or outflow ? • Disk • Linear structure and velocity gradient => Edge-on rotating disk • Ring structure (Bartkiewicz et al. 2005) • Infall ? (Goddi et al. 2007) • Outflow • Expanding shock (< 10 km s-1) (Walsh et al. 1998) • Parallel to H2 emission (De Buizer 2003) • Planar shock (Dodson et al. 2004) G 327.120+0.511 (Phillips et al. 1998) G 320.23-0.28 (De Buizer 2003)

  5. Purpose and approach Clarify associating sites of methanol maser • indirectly : superpose on other probes • water, OH masers • continuum : UC HII regions, dust emissions • molecular lines : outflow, rotating disk • directly : internal proper motions • measure at three epochs

  6. Target : Onsala 1

  7. Nagayama et al. (2008a) Target : Onsala 1 (ON 1) • distance : 1.75 kpc (Rygl et al. in 9th EVN symp.) • multiple location of MSFRs • outflows in various directions • water masers, CO, H2 • H13CO+, SiO • Clear absolute position of methanol maser • measured with the MERLIN (Green et al. 2007) • mapping toward only red-shifted spectral feature CH3OH maser Kumar et al. (2004)

  8. Observational tablewith the JVN at 6.7 GHz • velocity resolution : 0.176 km s-1 • synthesized beam : ~ 5×3 mas2 • phase referencing Y:Yamaguchi 32-m, U:Usuda 64-m, M:Mizusawa 20-m, I:Ishigaki 20-m, R:Iriki 20-m, O:Ogasawara 20-m ＊unit : mJy beam-1

  9. Results

  10. ON 1 --- I : Spatial distribution • Separated (spectrum) : ～15 km s-1 • Boundary of systemic velocity • CS (J=2‐1) : 11.6±3.0 km s-1 • H76α : 5.1±2.5 km s-1 • Isolated (spatial) : ～1800 AU • northeast-southwest direction Vsys ~12 km s-1 H76 ~5.1 km s-1

  11. ON 1 --- II : Superposition • Associated with the UC HII region • Coincided with OH maser • Separated from water maser • different exciting sources • Coincided with the H13CO+, SiO outflows • Northeast-southwest • PA ~ 44 deg • Low speed : 4.5 km s-1 • ~30 times smaller spatial size • Similar trend for radial velocity • northeast : blue-shifted southwest : red-shifted Nagayama et al. (2008a) modified by our works

  12. ON 1 --- III : Internal proper motion • Identified 13 spots • within 4 mas (motion) • within 0.18 km s-1 (radial) • Direction • roughly Northeast-southwest • coincided with H13CO+, SiO • Velocity of motions • 0.4 ~ 7.0 km s-1 • Mean value : 3.2 km s-1 • Similar to H13CO+ : 4.5 km s-1 tracing Outflow ?

  13. ON1 --- IV : Comparison with OH masers • OH maser • Expanding motions（Fish & Reid 2007） • Tracing expanding UC HII region • Methanol maser • Similar to OH maser • direction of motions • spatial coincidence • radial velocities tracing the expanding UC HII region ? Fish & Reid (2007)の図を改変

  14. Expanding shell model • Expanding shell model (Nagayama et al. 2008b) • Vsys: H76α~5.1 km s-1 • apply to the OH masers (Fish & Reid 2007) • vexp ~5.4 km/s • rshell~1330 mas • Unsuitable for methanol masers • particularly blue-shifted spots different from expanding motions of the OH masers referred from Nagayama et al. (2008b)

  15. 6.7 GHz methanol maser in ON 1 Isolated in spatial distribution and spectrum Superposition coincide with the UC HII region, H13CO+, SiO outflows Internal proper motion directed away between red- and blue-shifted spots roughly northeast-southwest direction Comparison with the OH masers similar : spatial, radial velocity, proper motion Unsuitable the expanding shell model of OH masers Summary possibly tracing Outflow

  16. Prospects • Measuring internal proper motions toward many methanol sources with EAVN • play a significant role in a development of EAVN • Array construct • Shanghai (will be installed) • make UV-coverage in east-west direction • Urumqi • form maximum baseline ~3 times longer than that now • Australian stations • advantage for observations of equatorial sources

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