Three millimeter molecular line observations in sagittarius B2. I. Full synthesis mapping study of HNO, CCS, and HC¹³CCN

We present the first full synthesis maps of the small molecules HNO, CCS, and HC ¹³CCN in Sgr B2. We have observed the 3.8 mm continuum, the HNO J_{K-1 K1} = 1₀₁-0₀₀, the CCS J_N = 7₆-6₅, and the HC ¹³CCN J = 9-8 transitions in the core of the Sgr B2 molecular cloud, using the BIMA millimeter array and the NRAO 12 m telescope. We have found that HNO exists in five major gas clumps in the Sgr B2 region, which we have labeled HNO(N), HNO(NW), HNO(E), HNO(M), and HNO(S). Of particular interest is HNO(M), a major molecular gas concentration ∼15″ west of Sgr B2 (M) in a region of young star formation. HNO is found to be closely associated with the ionized gas and might be depleted around bright H II complexes. In general, the peak intensity of the HNO emission is found to be offset from the peak of the continuum emission. We found evidence for some chemical differentiation among the three species, HNO, CCS, and HC ¹³CCN, but the abundance ratios are in fair agreement with theoretical models. Two unidentified lines, U81420 and U81518, were observed, and a previously unknown compact dust source was detected. Our HNO data indicate the presence of a rotating ∼ (2.2-4.4) × 103 M_⊙ gas envelope surrounding Sgr B2(N), a possible bipolar gas outflow in HNO(M), and possibly a large (∼4.2 × 10⁴ M_⊙) extended rotating disk associated with HNO (S). In addition, the CCS and HC ¹³CCN data approximately outline the extended component of Sgr B2 and clearly show that the southern continuum source Sgr B2(S) is actually a major molecular source as well. Consequently, the kinematics of the Sgr B2 molecular cloud is quite complex, but in moving from the northwest to south, the LSR velocity generally changes from 79 to 46 km s^-1.