Water Vapor around Sgr B2

Abstract

We have conducted a study combining H2O lines in two spectral regions. First, Infrared Space Observatory observations of several H2O thermal lines seen in absorption toward Sgr B2(M) at a spectral resolution of 35 kms^-1 have been analyzed. Second, an IRAM-30m telescope map of the para-H2O 3_13-2_20 line at 183.31 GHz, seen in emission, has also been obtained and analyzed. The H2O lines seen in absorption are optically thick and are formed in the outermost gas of the condensations in front of the far-IR continuum sources. They probe a maximum visual extinction of ~5 to 10 mag. Radiative transfer models indicate that these lines are quite insensitive to temperature and gas density, and that IR photons from the dust play a dominant role in the excitation of the involved H2O rotational levels. The water vapor abundance in the region is (1-2)x10^-5. The relatively low H2O/OH abundance ratio in the region, 2-4, is a signature of UV photon dominated surface layers traced by far-IR observations.

17 pages, 10 figures (2 of them bitmapped to low resolution), 2 tables, accepted in ApJ, 2006, January 12

References in corpus (10)

• SiO emission from the Galactic Center Molecular Clouds
• Discovery of Interstellar Hydrogen Fluoride
• The far-IR spectrum of Sagittarius B2 region: Extended molecular absorption, photodissociation and photoionization
• Chandra Observations of Diffuse X-Rays from the Sagittarius B2 Cloud
• Far-Infrared OH fluorescent emission in Sagittarius B2
• Physical conditions in shocked regions of Orion from ground-based observations of H_2O
• Detection of HD in emission towards Sagittarius B2
• The line-of-sight distribution of water in the SgrB2 complex
• Submillimeter Wave Astronomy Satellite mapping observations of water vapor around Sagittarius B2
• Very Efficient Methods for Multilevel Radiative Transfer in Atomic and Molecular Lines

Cited by in corpus (37)

• Herschel observations of EXtraordinary Sources: Analysis of the full Herschel/HIFI molecular line survey of Sagittarius B2(N)
• The Submillimeter Array 1.3 mm line survey of Arp 220
• The Warm Molecular Gas Around the Cloverleaf Quasar
• The Physics of Water Masers observable with ALMA and SOFIA: Model Predictions for Evolved Stars
• Interstellar Detection of Methyl Isocyanate CH${}_3$NCO in Sgr B2(N): A Link from Molecular Clouds to Comets
• The Central 300 pc of the Galaxy probed by infrared spectra of H${}_3^{+}$ and CO: part I. Predominance of warm and diffuse gas and high H${}_2$ ionization rate
• Water absorption in Galactic translucent clouds: conditions and history of the gas derived from Herschel/HIFI PRISMAS observations
• The ionization fraction gradient across the Horsehead edge: An archetype for molecular clouds
• Herschel observations of the Sgr B2 cores: Hydrides, warm CO, and cold dust
• An ALMA multi-line survey of the ISM in two quasar host-companion galaxy pairs at $z>6$
• Spectral line survey of the ultracompact HII region Mon R2
• HIFI Spectroscopy of ${\mathrm{H}}_2\mathrm{O}$ submm Lines in Nuclei of Actively Star Forming Galaxies
• The ISO LWS high resolution spectral survey towards Sagittarius B2
• Herschel spectroscopic observations of the compact obscured nucleus in Zw 049.057
• Herschel / HIFI observations of CO, H2O and NH3 in Mon R2
• Solving radiative transfer with line overlaps using Gauss Seidel algorithms
• The Water Vapor Abundance in Orion KL Outflows
• The 35Cl/37Cl isotopic ratio in dense molecular clouds: HIFI observations of hydrogen chloride towards W3A
• A non-equilibrium ortho-to-para ratio of water in the Orion PDR
• Ground-state ammonia and water in absorption towards Sgr B2
• The abundance of C18O and HDO in the envelope and hot core of the intermediate mass protostar NGC 7129 FIRS 2
• Submillimeter imaging of the Galactic Center starburst Sgr B2. Warm molecular, atomic, and ionized gas far from massive star-forming cores
• Sub-arcsecond imaging of the water emission in Arp 220
• Herschel observations in the ultracompact HII region Mon R2: Water in dense Photon-dominated regions (PDRs)
• The Foggy Disks Surrounding Herbig Ae Stars: a Theoretical Study of the H2O Line Spectra
• Submillimeter and Millimeter Masers
• Herschel observations of deuterated water towards Sgr B2(M)
• Non--local radiative transfer in strongly inverted masers
• On the influence of collisional rate coefficients on the water vapour excitation
• The maser emitting structure and time variability of the SiS lines J=14-13 and 15-14 in IRC+10216
• Far-Infrared detection of H2D+ toward Sgr B2
• Sagittarius B2 Main: A Cluster of Ultra-Compact HII Regions and Massive Protostellar Cores
• A Search for H2O in the Strongly Lensed QSO MG 0751+2716 at z=3.2
• Distribution of Water Vapor in Molecular Clouds. II
• Extragalactic line surveys
• The far-IR view of Sgr B2 and Orion KL
• Interstellar Medium in Extremely High Star-Formation Regions: A Prospect of Observations on the Millimetron Space Observatory