No abstract available

No abstract available

[en] We present observations of SO² toward the Orion KL Nebula. Fourteen transitions of SO² and ₃₄SO², which span a range of excitation up to 365 K above the ground state, were detected. The SO² lines cannot be fitted by an optically thin source model with a single rotational temperature. Partial saturation of the strongest SO² lines and an increase in the rotational SO² rotation temperature probably indicates the kinetic temperature of the plateau source, since it agrees with other estimates of the kinetic temperature in this region. No strong variation in rotational temperature with velocity is found for at least the central +- 20 km s^-₁ of the SO² plateau. The size of the SO² emitting region in Orion was estimated to be < or =25'' based on maps obtained with the Onsala Space Observatory 20 m telescope (HPBW = 45''). This value is consistent with estimates of the plateau source size from SO and other molecules, and with the SO² line intensities produced by the thermal excitation model discussed in this paper. The ₃₄SO² lines are approx.30% stronger than would be predicted by the terrestrial S/₃₄S ratio, suggesting that either the isotope ratio is not terrestrial or the SO² population distribution is nonthermal. Since the thermal models are consistent with the observed SO² lines, the former explanation is the more attractive one. SO² was also sought in other sources and detected in W51, DR 21(OH), and W3(OH). Observations of these sources suggest that SO² is probably partially saturated and originates from small regions in the clouds. We also tabulate new observations of HC³N( J = 8→7) and H²CO(1⁰¹→0⁰⁰) in several sources

[en] The 3264-MHz transition of CH has been detected in three galaxies (the Large Magellanic Cloud, NGC 4945 and NGC 5128) and possibly in a fourth (NGC 253). The line profiles were similar to those for H₂CO. The 3335-MHz transition was detected in one (LMC) and possibly another (NGC 4945). With the exception of NGC 5128, the line/continuum ratios are similar to those in our Galaxy. The results suggest an overabundance of CH relative to H₂CO and OH in a molecular cloud in NGC 5128 which is probably located well in front of the nucleus. (author)

[en] The 2₁₁-2₁₂ transition of H₂CS, previously observed only towards Sgr B2, has been detected in absorption against a total of 11 continuum sources. A comparison of the results with profiles of the 1₁₀-1₁₁ transition of H₂CO yields a rest frequency of 3139.391 +- 0.002 MHz for the H₂CS transition. The tau(H₂CO)/tau(H₂CS) optical depth ratios lie in the range 100 to 340. The [H₂CO]/[H₂CS] abundance ratios, derived assuming a similarity in excitation of the two molecular species, have an average value less than half the value (40) for the [O]/[S] cosmic abundance ratio. In contrast, the mean [CO]/[CS] ratio greatly exceeds 40. (author)

[en] We report the first detection in cold dark clouds of methyl acetylene (CH₃CCH) and the butadiynyl radical (C₄H). The 2₀ → 1₀ and 2₁ → 1₁ transitions of CH₃CCH and the hyperfine-resolved N = 3 → 2 transitions of C₄H, which occur at frequencies near 34 and 29 GHz, respectively, are all seen astronomically for the first time. The distribution of CH₃CCH in TMC--1 appears to correlate with that of the cyanopolyynes, and not with NH₃ or CN. Abundance ratios at the TMC--1 HC₅N peak include [CH₃C₂H]/[HC₂CN]roughly-equal1, [C₄H]/[C₂H]roughly-equal1, and [C₄H]/[HC₄CN]roughly-equal4

[en] HCN has been mapped with 42'' spacing (=HPBW) around the BN type IR source S 235B (=IRS 4). The HCN hyperfine structure is well resolved and departs from LTE. The ratio R₁₂, which in LTE lies between 0.6 and 1.0, is approximately 0.28, i.e. far outside the LTE range. H¹³CN has also been detected in two positions. The HCN column density toward S 235B is >8.0x10¹³ cm^-2. (Auth.)

[en] A new interstellar molecule, methylcyanoacetylene (CH₃C₃N), has been detected in the molecular cloud TMC-1. The J = 8 → 7, J = 7 → 6, J = 6 → 5, and J = 5 → 4 transitions have been observed. For the first three of these, both the K = 0 and K = 1 components are present, while for J = 5 → 4, only the K = 0 line has been detected. The observed frequencies were calculated by assuming a value of radial velocity V/sub lSR/ = 5.8 km s^-1 for TMC-1, typical of other molecules in the cloud. All Observed frequencies are within 10 kHz of the calculated frequencies, which are based on the 1982 laboratory constants of Moises et al., so the identification is secure. The lines are broadened by hyperfine splitting, and the J = 5 → 4, K = 0 transition shows incipient resolution into three hyperfine components. The rotational temperature determined from these observations is quite low, with 2.7 K< or =T/sub rot/< or =4 K. The total column density is approximately 5 x 10¹² cm^-2

[en] Some 25 previously unreported intestellar lines have been detected in the 3--4 mm spectrum of Orion A and are attributed to methyl formate (HCOOCH₃). A rotational temperature T> or approx. =50 K and a beam-averaged column density Nroughly-equal2(10)¹⁴ cm^-2 are estimated. A new limit on the abundance of formic acid suggests that [HCOOCH₃]/[HCOOH]> or approx. =3. Methyl formate transitions at 76.702 and 76.711 GHz, at 85.927 GHz and at 86.224 GHz clearly correspond to previously reported spectral lines attributed to CH₄, NH₂D, and (CH₃)₂O, respectively. These results suggest that the detections of methane and deuterated ammonia in Orion A should be regarded as tentative only, with important implications for interstellar chemistry and deuterium abundances