Submillimeter Wave Astronomy Satellite mapping observations of water vapor around Sagittarius B2

Abstract

Observations of the 1(10)-1(01) 556.936 GHz transition of ortho-water with the Submillimeter Wave Astronomy Satellite (SWAS) have revealed the presence of widespread emission and absorption by water vapor around the strong submillimeter continuum source Sagittarius B2. An incompletely-sampled spectral line map of a region of size 26 x 19 arcmin around Sgr B2 reveals three noteworthy features. First, absorption by foreground water vapor is detectable at local standard-of-rest (LSR) velocities in the range -100 to 0 km/s at almost every observed position. Second, spatially-extended emission by water is detectable at LSR velocities in the range 80 to 120 km/s at almost every observed position. This emission is attributable to the 180-pc molecular ring identified from previous observations of CO. The typical peak antenna temperature of 0.075 K for this component implies a typical water abundance of 1.2E-6 to 8E-6 relative to H2. Third, strong absorption by water is observed within 5 arcmin of Sgr B2 at LSR velocities in the range 60 to 82 km/s. An analysis of this absorption yields a H2O abundance ~ 2E-7 to 4E-7 relative to H2 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 the water absorption originates in the warm, foreground layer of gas proposed previously as the origin of ammonia absorption observed toward Sgr B2.

arXiv comment29 pages (AASTeX), including 9 postscript figures, to appear in the Astrophysical Journal

References in corpus (4)

• Discovery of Interstellar Hydrogen Fluoride
• Water Abundance in Molecular Cloud Cores
• Far-Infrared OH fluorescent emission in Sagittarius B2
• The line-of-sight distribution of water in the SgrB2 complex

Cited by in corpus (13)

• Water, O2 and Ice in Molecular Clouds
• The far-IR spectrum of Sagittarius B2 region: Extended molecular absorption, photodissociation and photoionization
• The far-infrared spectrum of Arp 220
• The Warm Molecular Gas Around the Cloverleaf Quasar
• Water Vapor around Sgr B2
• The ISO LWS high resolution spectral survey towards Sagittarius B2
• Rotational quenching of rotationally-excited H${}_2$O in collisions with He
• Ground-state ammonia and water in absorption towards Sgr B2
• Distribution of Water Vapor in Molecular Clouds
• Herschel observations of deuterated water towards Sgr B2(M)
• Broadband analysis techniques for Herschel/HIFI spectral surveys of chemically rich star-forming regions
• Upper limits to the water abundance in starburst galaxies
• Herschel water maps towards the vicinity of the black hole Sgr A*