1. Loránt Sjouwerman, Ylva Pihlström & Vincent Fish

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 (CH 3 OH)  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 20-50 km/s  Brightness T >> 10 5 K  Definitely maser ! (First time this is derived)

9. 1720 MHz OH and 36.2 GHz CH 3 OH  Collisionally excited  Similar gas  n(H) ~ 10 4 to 10 5 cm -3  T k ~ 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 CH 3 OH  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

11. HCN and 36.2 GHz CH 3 OH  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 CH 3 OH  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. NH 3 (3,3) and 36.2 GHz CH 3 OH  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!