A 1.3 cm Line Survey toward Orion KL

摘要: Orion KL has served as a benchmark for spectral line searches throughout the (sub)millimeter regime. The main goal is to systematically study characteristics of in 1.3 cm band. We carried out survey (17.9 GHz 26.2 GHz) with Effelsberg-100 m telescope towards KL. find 261 lines, yielding an average density about 32 features per above 3$\sigma$. identified lines include 164 radio recombination (RRLs) and 97 molecular lines. A total 23 transitions from species known exist are detected first time interstellar medium. Non-metastable 15NH3 time. Based on velocity information ALMA images, spatial origins emission constrained discussed. narrow feature found SO2 ($8_{1,7}-7_{2,6}$), possibly suggesting presence maser line. Column densities fractional abundances relative H2 estimated 12 molecules LTE methods. Rotational diagrams non-metastable 14NH3 J=K+1 J=K+4 yield different results; metastable have higher excitation temperature than 15NH3, indicating that they may trace regions. Elemental isotopic abundance ratios estimated: 12C/13C=63+-17, 14N/15N=100+-51, D/H=0.0083+-0.0045. dispersion He/H derived H$\alpha$/He$\alpha$ pairs H$\delta$/He$\delta$ very small, which consistent theoretical predictions departure coefficients bn factors hydrogen helium nearly identical. non-LTE code neglecting by infrared radiation field likelihood analysis, we denser regions lower kinetic temperature, favors external heating Hot Core.