Infall and outflow of molecular gas in Sgr B2

Sheng Li Qin, Jun Hui Zhao, James M. Moran, Daniel P Marrone, Nimesh A. Patel, Jun Jie Wang, Sheng Yuan Liu, Yi Jehng Kuan

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Observations of two H2CO (303-202 and 321-220) lines and continuum emission at 1.3 mm toward 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 redshifted and blueshifted outflow components have a common terminal velocity. This terminal velocity is 58 ±2 km s-1. It provides an excellent method for 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 redshifted 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 multilevel system with LVG approximation. The observed H2CO 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 H2CO(3 21-220) and the lower energy level transition H 2CO(321-220) is reversed in the redshifted 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 H2CO emission in Sgr B2(M) is discussed.

Original languageEnglish (US)
Pages (from-to)353-372
Number of pages20
JournalAstrophysical Journal
Volume677
Issue number1
DOIs
StatePublished - Apr 10 2008
Externally publishedYes

Fingerprint

molecular gases
outflow
terminal velocity
spectral mixture analysis
continuums
gas
energy levels
clumps
masers
molecular clouds
massive stars
gases
ladders
radiative transfer
energy
star formation
filaments
dust
inversions
approximation

Keywords

  • Galaxy: center
  • ISM: individual (Sgr B2)
  • ISM: kinematics and dynamics
  • ISM: molecules
  • Radio lines: ISM
  • Stars: formation

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Qin, S. L., Zhao, J. H., Moran, J. M., Marrone, D. P., Patel, N. A., Wang, J. J., ... Kuan, Y. J. (2008). Infall and outflow of molecular gas in Sgr B2. Astrophysical Journal, 677(1), 353-372. https://doi.org/10.1086/529067

Infall and outflow of molecular gas in Sgr B2. / Qin, Sheng Li; Zhao, Jun Hui; Moran, James M.; Marrone, Daniel P; Patel, Nimesh A.; Wang, Jun Jie; Liu, Sheng Yuan; Kuan, Yi Jehng.

In: Astrophysical Journal, Vol. 677, No. 1, 10.04.2008, p. 353-372.

Research output: Contribution to journalArticle

Qin, SL, Zhao, JH, Moran, JM, Marrone, DP, Patel, NA, Wang, JJ, Liu, SY & Kuan, YJ 2008, 'Infall and outflow of molecular gas in Sgr B2', Astrophysical Journal, vol. 677, no. 1, pp. 353-372. https://doi.org/10.1086/529067
Qin SL, Zhao JH, Moran JM, Marrone DP, Patel NA, Wang JJ et al. Infall and outflow of molecular gas in Sgr B2. Astrophysical Journal. 2008 Apr 10;677(1):353-372. https://doi.org/10.1086/529067
Qin, Sheng Li ; Zhao, Jun Hui ; Moran, James M. ; Marrone, Daniel P ; Patel, Nimesh A. ; Wang, Jun Jie ; Liu, Sheng Yuan ; Kuan, Yi Jehng. / Infall and outflow of molecular gas in Sgr B2. In: Astrophysical Journal. 2008 ; Vol. 677, No. 1. pp. 353-372.
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AU - Moran, James M.

AU - Marrone, Daniel P

AU - Patel, Nimesh A.

AU - Wang, Jun Jie

AU - Liu, Sheng Yuan

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AB - Observations of two H2CO (303-202 and 321-220) lines and continuum emission at 1.3 mm toward 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 redshifted and blueshifted outflow components have a common terminal velocity. This terminal velocity is 58 ±2 km s-1. It provides an excellent method for 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 redshifted 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 multilevel system with LVG approximation. The observed H2CO 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 H2CO(3 21-220) and the lower energy level transition H 2CO(321-220) is reversed in the redshifted 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 H2CO emission in Sgr B2(M) is discussed.

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KW - Radio lines: ISM

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