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36.2 GHz Methanol Masers in Sagittarius A

Loránt Sjouwerman , Ylva Pihlström & Vincent Fish. 36.2 GHz Methanol Masers in Sagittarius A. Outline. Introduction to Sagittarius A ( Sgr A) Introduction to 36.2 GHz methanol (CH3OH) Previous methanol observations in Sgr A New receivers at the EVLA (Ka band: 27-40 GHz)

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36.2 GHz Methanol Masers in Sagittarius A

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  1. LorántSjouwerman, YlvaPihlström & Vincent Fish 36.2 GHz Methanol Masersin Sagittarius A

  2. Outline Introduction to Sagittarius A (Sgr A) Introduction to 36.2 GHz methanol (CH3OH) Previous methanol observations in Sgr A New receivers at the EVLA (Ka band: 27-40 GHz) 36.2 GHz methanol is indeed a maser Comparison with: OH, HCN, 44.1 GHz CH3OH, NH3(3,3) Summary

  3. Sagittarius A (radio) scene • Galactic Center • Black Hole • Sgr A* • Circumnuclear Disk • Sgr A West or CND • Supernova Remnants • Sgr A East, G359.02-0.09 • Lots of stars and gas • M-0.02-0.07, M-0.23-0.08 • Interactions • e.g. 1720 MHz OH 50-70 km/s • Complex !

  4. Sagittarius A (radio) scene • Galactic Center • Black Hole • Sgr A* • Circumnuclear Disk • Sgr A West or CND • Supernova Remnants • Sgr A East, G359.02-0.09 • Lots of stars and gas • M-0.02-0.07, M-0.23-0.08 • Interactions • e.g. 1720 MHz OH 50-70 km/s • Complex !

  5. Methanol (CH3OH) • Class I and Class II methanol • Class I: mostly near outflows and shock regions: collisionally pumped (e.g. 36.2 GHz, 44.1 GHz) • Class II: mostly at and in star forming regions: radiatively pumped (e.g. 6.7 GHz, 12.2 GHz) • Thermal and/or masers • 36.2 GHz only single dish; 36.2 GHz masers ? • 36.2 GHz CH3OH and 1720 MHz OH: similar gas

  6. Single dish 36.2 GHz in Sgr A • Single dish observations • Szczepanski et al. 1989, 1991 • Large scale distribution • M-0.13-0.08, M-0.02-0.07 • High-density gas • Interaction and/or infall ? • Small scale distribution? • Need interferometer • No 36.2 GHz receivers

  7. Expanded Very Large Array • NRAO is currently rebuilding the VLA • e.g. new Ka band receivers • 27 to 40 GHz • 36.2 GHz CH3OH • Observe Sgr A at 36.2 GHz with (E)VLA ! • Special call for proposals • March 2009, in (incomplete) B configuration • Only 9 antennas outfitted, VLA correlator • New Observation Preparation Tool (OPT)

  8. 36.2 GHz in Sgr A using (E)VLA • Several 68” pointings • With 7 antennas, 0.3” • Point sources only • Many detections • Strong and narrow • Emission in sidelobes • Velocity 20-50km/s • Brightness T >> 105 K • Definitely maser ! (First time this is derived)

  9. 1720 MHz OH and 36.2 GHz CH3OH • Collisionally excited • Similar gas • n(H) ~ 104 to 105 cm-3 • Tk ~ 80 to 100 K • Nearby, but • Not co-spatial (>6.5”) • Velocities differ • Different tracers • Different shocks (in l.o.s.) • Different regions (in l.o.s.)

  10. HCN and 36.2 GHz CH3OH • Dense HCNclumps (red) • Star formation sites ? • 44.1 GHz methanol (o) and 22.2 GHz H2O masers (+) • Yusef-Zadeh et al. 2008 • 36.2 GHz methanol (x) • Debatable: • GBT has ~15” beam • No young massive stars • No radiatively pumped CH3OH or OH masers • H2O maser has many origins

  11. HCN and 36.2 GHz CH3OH • Dense HCN clumps (red) • Star formation sites ? • 44.1 GHz methanol (o) and 22.2 GHz H2O masers (+) • Yusef-Zadeh et al. 2008 • 36.2 GHz methanol (x) • Debatable: • GBT has ~15” beam • No young massive stars • No radiatively pumped CH3OH or OH masers • H2O maser has many origins

  12. 44.1 GHz and 36.2 GHz CH3OH • Both Class I, i.e. collisions or outflows • 36.2 and 44.1 GHz may be cospatial(see “G”) • Single 44.1 GHz masers • Single 36.2 GHz masers • Here not sensitive to extended thermal methanol emission

  13. NH3(3,3) and 36.2 GHz CH3OH • HCN contours (i.e. CND) • Montero-Castaño et al. 2009 • NH3(3,3) colors • McGary et al. 2001 • 36.2 GHz CH3OH masers at NH3(3,3) peaks, tips of extensions toward CND Also 44.1 GHz at NH3(3,3) peak • Gas infall, where it collides with CND ?

  14. Summary First interferometric observations at 36.2 GHz Excellent new EVLA Ka band receivers(27-40 GHz) 36.2 GHz methanol maser emission 36.2 GHz methanol and 1720 MHz OH probably trace different shock regions (in Sgr A) Class I 44.1 and 36.2 GHz methanol may coexist No clear relation to HCN clumps or star formation Correlated with NH3(3,3), dense cloud collisions ? New science with EVLA is coming!

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