Infall and Outflow of Molecular Gas in Sgr B2

Abstract

Observations of two H${}_2$CO ($3_{03}-2_{02}$ and $3_{21}-2_{20}$) lines and continuum emission at 1.3 mm towards Sgr B2(N) and Sgr B2(M) have been carried out with the SMA. The mosaic maps of Sgr B2(N) and Sgr B2(M) in both continuum and lines show a complex distribution of dust and molecular gas in both clumps and filaments surrounding the compact star formation cores. We have observed a decelerating outflow originated from the Sgr B2(M) core, showing that both the red-shifted and blue-shifted outflow components have a common terminal velocity. This terminal velocity is 58$\pm$2 km s${}^{-1}$. It provides an excellent method in determination of the systematic velocity of the molecular cloud. The SMA observations have also shown that a large fraction of absorption against the two continuum cores is red-shifted with respect to the systematic velocities of Sgr B2(N) and Sgr B2(M), respectively, suggesting that the majority of the dense molecular gas is flowing into the two major cores where massive stars have been formed. We have solved the radiative transfer in a multi-level system with LVG approximation. The observed H${}_2$CO line intensities and their ratios can be adequately fitted with this model for the most of the gas components. However, the line intensities between the higher energy level transition H${}_2$CO ($3_{21}-2_{20}$) and the lower energy level transition H${}_2$CO ($3_{03}-2_{02}$) is reversed in the red-shifted outflow region of Sgr B2(M), suggesting the presence of inversion in population between the ground levels in the two K ladders (K${}_{-1}$= 0 and 2). The possibility of weak maser processes for the H${}_2$CO emission in Sgr B2(M) is discussed.

44 pages, 14 figures Accepted for publication in The Astrophysical Journal

References in corpus (2)

• A deep submillimetre survey of the Galactic Centre
• The far-IR spectrum of Sagittarius B2 region: Extended molecular absorption, photodissociation and photoionization

Cited by in corpus (31)

• The physical and chemical structure of Sagittarius B2. II. Continuum millimeter emission of SgrB2(M) and SgrB2(N) with ALMA
• Submillimeter continuum observations of Sagittarius B2 at subarcsecond spatial resolution
• ATLASGAL-selected massive clumps in the inner Galaxy: VI. Kinetic temperature and spatial density measured with formaldehyde
• Discovery of an extremely wide-angle bipolar outflow in AFGL 5142
• Localizing Sagittarius A* and M87 on Microarcsecond Scales with Millimeter VLBI
• Star formation in 'the Brick': ALMA reveals an active proto-cluster in the Galactic centre cloud G0.253+0.016
• ALMA Observations of Massive Clouds in the Central Molecular Zone: Ubiquitous Protostellar Outflows
• Nature of W51e2: Massive Cores at Different Phases of Star Formation
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde. III. The Orion Molecular Cloud 1
• Infall and outflow motions in the high-mass star forming complex G9.62+0.19
• Kinetic temperature of massive star forming molecular clumps measured with formaldehyde. II. The Large Magellanic Cloud
• Uniform Infall toward the Cometary H II Region in the G34.26+0.15 Complex?
• Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies
• A study of dynamical processes in the Orion KL region using ALMA-- Probing molecular outflow and inflow
• Sgr B2(N): A bipolar outflow and rotating hot core revealed by ALMA
• First detection of the carbon chain molecules 13CCC and C13CC towards SgrB2(M)
• The Emission Structure of Formaldehyde MegaMasers
• Relating Kerr SMBHs in Active Galactic Nuclei to RAD configurations
• Discovery of 14NH3 (2,2) maser emission in Sgr B2-Main
• High-Resolution Observations of Molecular Lines toward the Hot Core G28.20-0.04N
• Sub-arcsec Observations of NGC 7538 IRS 1: Continuum Distribution and Dynamics of Molecular Gas
• Multiwavelength investigation of extended green object G19.88-0.53: Revealing a protocluster
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde V. The massive filament DR21
• Sagittarius B2 Main: A Cluster of Ultra-Compact HII Regions and Massive Protostellar Cores
• SOFIA-upGREAT imaging spectroscopy of the [C II] 158um fine structure line of the Sgr B region in the Galactic center
• Properties and Keplerian Rotation of the Hot Core IRAS 20126+4104
• Dust and HCO+ Gas in the Star Forming Core W3-SE
• Outflow and accretion detections in the young stellar object IRAS 04579+4703
• CO J=2-1 and CO J=3-2 observations toward the high-mass protostellar candidate IRAS 20188+3928
• Radiation-driven Implosion in the Cepheus B Molecular Cloud
• Dense, Parsec-Scale Clumps near the Great Annihilator