Journal of The Korean Astronomical Society (천문학회지)

The Korean Astronomical Society (한국천문학회)
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CHEMICAL DIAGNOSTICS OF THE MASSIVE STAR CLUSTER-FORMING CLOUD G33.92+0.11. III. 13CN AND DCN

  • Received : 2019.03.05
  • Accepted : 2019.05.24
  • Published : 2019.06.30
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Abstract

Using ALMA observations of the $^{13}CN$ and DCN lines in the massive star-forming region G33.92+0.11A, we investigate the CN/HCN abundance ratio, which serves as a tracer of photodissociation chemistry, over the whole observed region. Even considering the uncertainties in calculating the abundance ratio, we find high ratios (${\gg}1$) in large parts of the source, especially in the outer regions of star-forming clumps A1, A2, and A5. Regions with high CN/HCN ratios coincide with the inflows of accreted gas suggested by Liu et al. (2015). We conclude that we found strong evidence for interaction between the dense gas clumps and the accreted ambient gas which may have sequentially triggered the star formation in these clumps.

Keywords

CMHHBA_2019_v52n3_83_f0001.png 이미지

Figure 1. Continuum map at 1.3mm (after subtracting a free-free emission model, Liu et al. 2015). The intensity scale at the top is in units of Jy beam−1. The white contour line marks a continuum emission strength of 3 mJy beam−1. A1, A2, and A5 indicate the clumps containing the dust emission peaks number 1, 2, and 5 of G33.92+0.11A, respectively (Liu et al. 2012). The black cross denotes the position of the UC HII region.

CMHHBA_2019_v52n3_83_f0002.png 이미지

Figure 2. Map of the integrated intensity of DCN 3 − 2. The intensity scale (in units of Jy beam−1 km s−1) is shown at the top. The white contour outlines the continuum emission shown in Figure 1. The black cross marks the position of the UC Hii region. A sample spectrum taken at the position of the emission peak (α, δ)J2000 = (18h52m50s.42, 00°55'26''.66) is shown in the inset in the top-right corner. Its abscissa shows vlsr (in km s−1) and its ordinate shows the ux density (in K).

CMHHBA_2019_v52n3_83_f0003.png 이미지

Figure 3. Same as Figure 2 but for 13CN N = 2 − 1. The emission peak is located at (α, δ)J2000 = (18h52m50s.02, 00°55'28''.12).

CMHHBA_2019_v52n3_83_f0004.png 이미지

Figure 4. Column density ratio of CN/HCN derived from 13CN and DCN intensities. The color bar at the top shows the range of abundance ratios. The white cross marks the position of the UC Hii region. The white contour is the 0.02 Jy beam−1 km s−1 strength of the CN N = 2 line emission in Figure 3.

Table 1 Line parameters for the spectra in Figures 2 and 3 and abundances

CMHHBA_2019_v52n3_83_t0001.png 이미지

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