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The Extended Methanol Maser Emission in W51

The Extended Methanol Maser Emission in W51. Chris Phillips ATNF CSIRO. Chris.Phillips@csiro.au. Methanol Masers. Methanol has rich microwave spectrum Many masing transitions Strongest emission at 6.7 GHz Only seen towards regions of massive star formation

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The Extended Methanol Maser Emission in W51

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  1. The Extended Methanol Maser Emission in W51 Chris Phillips ATNF CSIRO Chris.Phillips@csiro.au

  2. Methanol Masers • Methanol has rich microwave spectrum • Many masing transitions • Strongest emission at 6.7 GHz • Only seen towards regions of massive star formation • Many sources have linear structure with velocity gradients – Discs? • May be a good tracer of massive protostars

  3. W51 • One of most luminous regions of massive star formation in the galaxy • Distance of 7 kpc (1” == 0.03pc) • Many distinct components • Strongest “d” and “e” in 1 arcminute region

  4. ATCA Observations FWHM of Effelsberg at 6.7 GHz ATCA Observations • Observed 6.7-GHz methanol maser emission towards ~20 northern methanol maser sources • ATCA only connected element interferometer which can observe 6.7 GHz

  5. EVN Observations • Observed Feb 2002 • 4 stations only: Effelsberg, Torun, Jodrell Bank and Onsala • Two fields of view • Phase referenced with a 3-6-6 minute duty cycle • Correlated at JIVE with a single pass and a 2 second integration time • Dual polarisation with 1024 spectral points per pol

  6. EVN Observations • EVN • ATCA

  7. • Greyscale Methanol Masers VLA 3.6 GHz continuum Mehringer etal 1994, ApJSS, 91 713 60” / 2pc

  8. • • • Methanol OH Water 3.6 cm VLA continuum (0.2”) W51 IRS 2 W51 Main Gaume etal, 1993 ApJ 417 645 Argon etal, 2000, ApJSS, 129, 159 Imai etal, 2002, PASJ, 54, 741

  9. • • • - Methanol OH Water NH3 (1,1) W51 Main e2 e4 Zhang etal, 1997 ApJ 488, 241 e1 e3

  10. M = 90 M

  11. • • • - Methanol OH Water NH3 (1,1) W51 Main: e2 2” 0.06 pc

  12. • • • • - Methanol OH Water SiO NH3 (1,1) W51 d/IRS 2 Eisner etal, 2002, ApJ, 569, 334

  13. + + NH3(9,8) maser

  14. Spectral Type B0.5 Size <300 AU EM = 5.9x109  = 2.1

  15. Conclusions • We have made phased referenced, wide field spectral line observations of the 6.7 GHz methanol maser emission in W51 • The methanol traces a number of previously unreported regions of star formation • The linear maser emission in W51-main probably traces edge of HII rather than disc • The methanol in W51-d2 is associated with a very compact, very young HII region

  16. Ralph Gaume David Mehringer Alice Argon Josh Eisner Qizhou Zhang Hiroshi Imai Paolo Persi Antonio Chrysostom Acknowledgments With many thanks to: Overlays made using the package formally known as aips++

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