A Submillimeter HCN Laser in IRC+10216

We report the detection of a strong submillimeter wavelength HCN laser line at a frequency near 805 GHz toward the carbon star IRC+10216. This line, the J=9-8 rotational transition within the (04(0)0) vibrationally excited state, is one of a series of HCN laser lines that were first detected in the laboratory in the early days of laser spectroscopy. Since its lower energy level is 4200 K above the ground state, the laser emission must arise from the inner part of IRC+10216's circumstellar envelope. To better characterize this environment, we observed other, thermally emitting, vibrationally excited HCN lines and find that they, like the laser line, arise in a region of temperature approximately 1000 K that is located within the dust formation radius; this conclusion is supported by the linewidth of the laser. The (04(0)0), J=9-8 laser might be chemically pumped and may be the only known laser (or maser) that is excited both in the laboratory and in space by a similar mechanism.Comment: 11 pages, 3 figure

W51 IRS 2: A Massive Jet Emerging from a Molecular Cloud into an H II Region

We have mapped [Ne II] (12.8um) and [S IV] (10.5um) emission from W51 IRS 2 with TEXES on Gemini North, and we compare these data to VLA free-free observations and VLT near-infrared images. With 0.5" spatial and 4 km/s spectral resolution we are able to separate the ionized gas into several components: an extended H II region on the front surface of the molecular cloud, several embedded compact H II regions, and a streamer of high velocity gas. We interpret the high velocity streamer as a precessing or fan-like jet, which has emerged from the molecular cloud into an OB star cluster where it is being ionized.Comment: 3 pages, 4 figures, 2 movie

LOCATING COMPLEX, SATURATED ORGANIC MOLECULES IN THE INTERSTELLAR MEDIUM

Author Institution: Department of Astronomy, University of IllinoisAstronomers have known for two decades now that the chemistry of the interstellar medium can be quite interesting. Millimeter wavelength lines of complex, saturated organic molecules such as methyl formate $(HCOOCH_{3})$, ethyl cyanide $(CH_{3}CH_{2}CN)$, and ethanol $(CH_{3}CH_{2}OH)$ were first detected more than two decades ago. Recently, we have exploited advances in millimeter interferometry to pinpoint the locations of these sources. We have surveyed several regions containing these molecules and have been able to develop a unified empirical picture of the environment in which they exist. Our results indicate these molecules exist in the gas phase only in the dense, dusty, hot cores of molecular cloud in which massive star formation has recently occurred. Our empirical picture supports models in which these complex species are formed on the surfaces of icy grains. After a nearby massive star forms, these molecules (or their precursors) are evaporated off the grains into the gas phase. This work was partially funded by NSF AST96-13999 and the University of Illinois

OBSERVATIONS OF FORMIC ACID TOWARD GALACTIC HOT MOLECULAR CORES

Author Institution: Department of Astronomy, University of IllinoisFormic acid shares structural elements with the common interstellar molecule methyl formate $(HCOOCH_{3})$ and the elusive biomolecule acetic acid $(CH_{3}COOH)$. It is the simplest organic acid, but it has only been identified in astronomical sources by fairly weak lines in single-element telescope surveys. In order to study the successive formation of biomolecules in the ISM, we carried out a survey of HCOOH toward galactic hot molecular cores with the Berkeley-Illinois-Maryland Association (BIMA) Array. Up to five transitions with rest frequencies near 87 GHz have been detected simultaneously in three sources: Sgr B2(N), Orion, and W51, HCOOH was found to have an excitation temperature of at least 100 K. The formation of HCOOH is probably related to grain-surface chemistry in hot cores. Abundance comparisons with other molecules such as $HCOOCH_{3}$ and ethyl cyanide $(C_{2}H_{5}CN)$ will be discussed. This work was partially funded by NSF AST96 - 13999 and the University of Illinois