F. J. Lovas

Interstellar Antifreeze: Ethylene glycol

Interstellar ethylene glycol ( ) has been detected in emission toward the Galactic center source HOCH CH OH 22 Sagittarius B2(N-LMH) by means of several millimeter-wave rotational torsional transitions of its lowest energy conformer. The types and kinds of molecules found to date in interstellar clouds suggest a chemistry that favors aldehydes and their corresponding reduced alcohols—e.g., formaldehyde ( )/methanol ( ), acetal- 2 any such large complex molecules are formed in the interstellar clouds, atomic hydrogen (H) and carbon monoxide (CO) could form formaldehyde on grain surfaces, but such surface chemistry beyond that point is uncertain. However, laboratory experiments have shown that the gas-phase reaction of atomic hydrogen (H) and solid-phase CO at 10-20 K can produce formaldehyde and methanol and that alcohols and other complex molecules can be synthesized from cometary ice analogs when subject to ionizing radiation at 15 K. Thus, the presence of aldehyde/ reduced alcohol pairs in interstellar clouds implies that such molecules are a product of a low-temperature chemistry on grain surfaces or in grain ice mantles. This work suggests that aldehydes and their corresponding reduced alcohols provide unique observational constraints on the formation of complex interstellar molecules. Subject headings: ISM: abundances — ISM: clouds — ISM: individual (Sagittarius B2(N-LMH)) — ISM: molecules — radio lines: ISM

Confirmation of Interstellar Acetone

We present new observations of interstellar acetone [(CH3)2CO] from both the NRAO 12 m and the BIMA array. We report NRAO 12 m detections of 13 new acetone emission features that can be assigned to 20 acetone transitions. These assignments are based on the measured and calculated frequencies in 2002 of Groner and coworkers, and they confirm the interstellar acetone identification in 1987 by Combes and coworkers. In addition, our BIMA array observations show that acetone emission is concentrated in the vicinity of the hot molecular core Sgr B2 (N-LMH). The beam-averaged column density for acetone is NT = 2.9(3) × 1016 cm-2. This value is consistent with the 1990 conclusions of Herbst, Giles, & Smith that the observed acetone abundance is too high to be explained by gas-phase synthesis reactions.

A Sensitive Very Large Array Search for Small-Scale Glycine Emission Toward OMC-1

We have conducted a deep Q-band (� � 7 mm) search with the Very Large Array (VLA) toward OMC-1 for the lowest energy conformation (conformer I) of glycine (NH2CH2COOH) in four rotational transitions: 615–514 ,6 24–523 ,7 17–616, and 707–606. Our VLA observations sample the smallest scale structures to date in the search for glycine toward OMC-1. No glycine emission features were detected. Thus, if glycine exists in OMC-1, it is below our detection limit, or it is more spatially extended than other large molecules in this source, or it is primarily in its high-energy form (conformer II). Our VLA glycine fractional abundance limits in OMC-1 are comparable to those determined from previous IRAM 30 m measurements—somewhat better or worse depending on the specific source model—and the entire � 1 0 primary beam of the VLA was searched while sensitive to an areal spatial scale � 150 times smaller than the 24 00 beam of the IRAM single-element telescope. In the course of this work, we detected and imaged the 414–313 A and E transitions of methyl formate (HCOOCH3) and also the 202–101 transition of formic acid (HCOOH). Since formic acid is a possible precursor to glycine, our glycine limits and formic acid results provide a constraint on this potential formation chemistry route for glycine in OMC-1. Subject headings: ISM: abundances — ISM: clouds — ISM: individual (OMC-1) — ISM: molecules — radio lines: ISM

An extensive galactic search for conformer II glycine

We have conducted the most extensive galactic search reported to date for conformer II glycine, a higher energy form of the simplest amino acid. The search utilized four glycine transitions at centimeter wavelengths and 21 at millimeter wavelengths to observe 18 galactic molecular sources and one comet. No conformer II glycine lines were detected and measurements of representative sources were used to compute upper limits on total column densities. Several unidentified lines were detected and are reported here with some suggested possible identifications.

Detection, identification, and observations of interstellar H/sup 13/CO/sup +/

Observations of interstellar H/sup 13/CO/sup +/ are presented, and results of the molecular-structure computations supporting this particular molecular identification are given. Preliminary values of integrated intensity of ratios of H/sup 12/CO/sup +//H/sup 13/CO/sup +/ have been found for the main HCO/sup +/ clouds. Searches for H/sup 12/C/sup 18/O/sup +/ were unsuccessful, and upper limits are given. U86.76, a new unidentfied interstellar molecular which may be methylcyanoacetylene, was detected in Sgr B2. (AIP)

New interstellar molecular transitions in the 2 millimeter range

We derive a Sgr B2 kinetic temperature of approx.47 K based on previously unreported observations of K components of the 9/sub K/-8/sub K/ transition of CH/sub 3/CHH. We report 2 mm range observations in galactic molecular clouds of the 15/sub 5,11/-16/sub 4,12/ and 10/sub 0,10/-9/sub 1,9/ transitions of SO/sub 2/, the 3,4--2,3 transition of SO, the 4,3--3,3 transition of /sup 34/SO, the 11/sub 0/-11/sub -/1E, 8/sub 0/--8/sub -/1E, and 2/sub 1/--3/sub 0/A/sup +/ transition of CH/sub 3/OH, the 18/sub 2,17/--17/sub 2,16/ transition of CH/sub 3/CH/sub 2/CN, the 17--16 transition of HC/sub 3/N, and transitions of unidentified molecular species at frequencies of 144244.8, 145017.5/154583.0, 145075.9, 146932.5, 150328.0, 153431.0, 153487.5, 153668.3, and 159915.6 MHz. We searched for but did not detect the 14/sub 14,0/--13/sub 13,0/, 14/sub 14,1/--13/sub 13,1/, 15/sub 15,0/--14/sub 14,0/, and 15/sub 15,1/--14/sub 14,1/ transitions of H/sub 2/SO/sub 4/, the 25/sub 0,25/--24/sub 0,24/ and 25/sub 1,25/--24/sub 1,24/ transitions of HCOCHO, the 4--3 transition of HCP, the 7--6 transition of OC/sup 18/O, and the 2/sub 12/--1/sub 11/ and 2/sub 02/--1/sub 01/ transitions of HNO in several galactic molecular sources. We discuss the present evidence for the existence of interstellar HNO.

Radio detection of interstellar DCO/sup +/

The J=1--0 transition of the deuterated formyl ion, DCO/sup +/, has been detected in emission from NGC 2264 and DR 21(OH) and from the cool dust cloud L134. Estimates for the column density ratios of H/sup 13/CO/sup +/ to DCO/sup +/ are given for NGC 2264 and DR 21(OH); lower limits for the ratios are given for five other clouds. The DCO/sup +/ dectection in L134 provides unique observational evidence in support of chemical fractionation. The L134 results also suggest that the dust clouds may act as repositories for primordial deuterium. (AIP)

Detection of the torsionally excited state of methanol in Orion A

We report the detection of torsionally excited methanol (CH/sub 3/OH,..nu../sub t/ = 1) in Orion A. Three emission lines have been observed in the region of 93 GHz to 100 GHz. These coincide with laboratory measurements for the 1/sub 0/-2/sub 1/ E, 6/sub 1/-5/sub 0/ E and blended 2/sub 1/-1/sub 1/ E and 2/sub 0/-1/sub 0/ E transitions of CH/sub 3/OH in its torsionally excited state which lies near 200 cm/sup -1/ (approx.290 K) above the ground state. Hence, torsionally excited methanol is a new temperature probe. No emission was detected from the 2/sub 0/-1/sub 0/ A transition which arises from levels near 300 cm/sup -1/ (approx.430 K) above the ground state. Several other weak features not attributable to methanol were also observed, and possible identifications are reported.

Observations of the SiC2 radical toward IRC + 10216 at 1.27 centimeters

The first centimeter-wave transition of the recently identified SiC/sub 2/ radical has been observed in the envelope of the evolved carbon star IR +10216. The excellent agreement between our measured astronomical rest frequency and the predicted frequency, and our measured line intensity support the SiC/sub 2/ identification. The high-resolution line profile and mapping data are used to estimate the size of the IRC +10216 SiC, envelope and the abundance of SiC/sub 2/ relative to H/sub 2/.

A radio search for interstellar phosphorus compounds

The J=1--0 and 3--2 transitions of phosphorus nitride, PN, with resolvable hyperfine components at 46.99 GHz and blended components at 140.97 GHz, and transitions of phosphine, PH/sub 3/, at 47.39 and 46.94 GHz, arising from a small induced dipole moment, have been searched for but not found in interstellar molecular clouds. The J=3/2--1/2, F=3/2--3/2 transition of nitric oxide, NO, and the J/sub K/-K+=16/sub 4,12/15/sub 5,11/ transition of sulfur dioxide, SO/sub 2/, have been detected in Orion and Sagittarius B2. An unidentified emission line, U140921.8 MHz, has been observed in IRC+10216.