We report on the detection of four rotating massive disks in two regions of high-mass star formation. The disks are perpendicular to known bipolar outflows and turn out to be unstable but long lived. We infer that accretion onto the embedded (proto)stars must proceed through the disks with rates of∼10 M⊙ yr . Subject headings: Stars: formation – Radio lines: ISM – ISM: molecules – ISM: individu...

We present high angular resolution ( 100) multitracer spectral line observations toward the hot molecular core (HMC) associatedwith G34.26+0.15 between 87 and 109 GHz.We havemapped emission from (1) complex nitrogenand oxygen-rich molecules such as CH3OH, HC3N, CH3CH2CN, NH2CHO, CH3OCH3, and HCOOCH3; (2) sulfurbearing molecules such as OCS, SO, and SO2; and (3) the recombination line H53 . At t...

The reaction between the radical and the stable hydrocarbon is one of the simplest 2 22 neutral-neutral hydrocarbon reactions in chemical models of dense interstellar clouds and carbon-rich circumstellar shells. Although known to be rapid at temperatures o300 K, the reaction has yet to be studied at lower temperatures. We present here ab initio calculations of the potential surface for this rea...

The gas phase spectrum of the cyclic C18 molecule recorded in the laboratory at a temperature typical of diffuse interstellar clouds is compared with absorption features toward Oph and HD 204827 in the 5730–5934 8 region. For the origin band at 5928.5 8 an upper limit to the column density of 1:8 ; 10 cm 2 is inferred. The origin band pattern in the laboratory spectrum changes on lowering the i...

We have used the Submillimeter Wave Astronomy Satellite to map the ground-state 110 → 101 transition of ortho-H2O at 557 GHz in the Orion molecular cloud. H2O emission was detected in Orion over an angular extent of about 20, or nearly 3 pc. The water emission is relatively weak, with line widths (3–6 km s−1) and VLSR velocities (9–11 km s−1) consistent with an origin in the cold gas of the mol...

Measurements using the Far Ultraviolet Spectroscopic Explorer (FUSE) show that the gas-phase D/H ratio in the solar neighborhood is highly variable and suggest that the elemental abundance of deuterium in the Galactic disk may be higher than previously thought. We investigate in this Letter the possible consequences of such an enhanced D/H ratio on the deuterium fractionation in singly and mult...

The largest noncyclic molecules detected in the interstellar medium (ISM) are organic with a straight-chain carbon backbone. We report an interstellar detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an abundance 0.4 times that of its straight-chain structural isomer. This detection suggests that branched carbon-chain molecules may be generally abundant in the ISM. Ou...

Introduction Because of a systematic enrichment in deuterium, the insoluble organic molecules (IOM) of the carbonaceous meteorites are generally considered to represent interstellar materials. However, since the D/H ratios in IOM remain much lower than those measured astronomically for organic molecules synthesized in the interstellar medium (ISM), no plausible process has been proposed to acco...

The first FUV (λλ 1350–1750Å) spectral imaging observations of the Eridanus superbubble, obtained with the SPEAR/FIMS mission, have revealed distinct fluorescent emission from molecular hydrogen. In this study, the observed emission features were compared with those from a photo-dissociation region model with assumed illuminating stellar fields. The result showed rather high line ratios of I158...

A recent submillimeter line survey of Orion KL claimed detection of SiH. This paper reports on GBT observations of the 5.7 GHz Λ-doubling transitions of SiH in Orion. Many recombination lines, including C164δ, are seen, but SiH is not detected. The nondetection corresponds to an upper limit of 1.5×1015 cm−2 (4σ) for the beam-averaged column density of SiH. This suggests that the fractional abun...