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Observations of the 1(10)-1(01) 556.936 GHz transition of ortho-water withthe Submillimeter Wave Astronomy Satellite (SWAS) have revealed the presence ofwidespread emission and absorption by water vapor around the strongsubmillimeter continuum source Sagittarius B2. An incompletely-sampled spectralline map of a region of size 26 x 19 arcmin around Sgr B2 reveals threenoteworthy features. First, absorption by foreground water vapor is detectableat local standard-of-rest (LSR) velocities in the range -100 to 0 km/s atalmost every observed position. Second, spatially-extended emission by water isdetectable at LSR velocities in the range 80 to 120 km/s at almost everyobserved position. This emission is attributable to the 180-pc molecular ringidentified from previous observations of CO. The typical peak antennatemperature of 0.075 K for this component implies a typical water abundance of1.2E-6 to 8E-6 relative to H2. Third, strong absorption by water is observedwithin 5 arcmin of Sgr B2 at LSR velocities in the range 60 to 82 km/s. Ananalysis of this absorption yields a H2O abundance ~ 2E-7 to 4E-7 relative toH2 if the absorbing water vapor is located within the core of Sgr B2 itself;or, alternatively, a water column density ~ 2.5E+16 to 4E+16 per cm2 if thewater absorption originates in the warm, foreground layer of gas proposedpreviously as the origin of ammonia absorption observed toward Sgr B2.Comment: 29 pages (AASTeX), including 9 postscript figures, to appear in the  Astrophysical Journa

Submillimeter Wave Astronomy SatelliteMapping Observations of Water Vapor around Sagittarius B2