We compare an evolutionary chemical model with simple empirical models of the abundance and with static chemical models. We focus on the prediction of molecular line profiles that are commonly observed in low mass star forming cores. We show that empirical models can be used to constrain evaporation radii and infall radii using lines of some species. Species with more complex abundance profiles...

We develop a method of analyzing radio frequency spectral line observations to derive data on the temperature, density, velocity, and molecular abundance of the emitting gas. The method incorporates a radiative transfer code with a new technique for handling overlapping hyperfine emission lines within the accelerated lambda iteration algorithm and a heuristic search algorithm based on simulated...

VLA observations of large-scale HI and OH absorption in the merging galaxy of NGC6240 are presented with 1 arcsec resolution. HI absorption is found across large areas of the extended radio continuum structure with a strong concentration towards the double-nucleus. The OH absorption is confined to the nuclear region. The HI and OH observations identify fractions of the gas disks of the two gala...

We report the results of a 5-field mosaic of the central 15pc of the Galaxy in the (1,1) and (2,2) lines of NH3. Two narrow filaments or streamers are seen running parallel to the Galactic plane. The southern streamer appears to carry gas directly toward the nuclear region from the 20 km seccloud. The eastern streamer, which we will denote the molecular ridge, appears to be the denser part of t...

A variety of polycyclic aromatic hydrocarbons (PAHs) are reported in carbonaceous chondrites (CCs) and the interstellar medium (ISM). Although PAHs CCs not as large those detected ISM, their carbon isotope composition is interpreted pinpointing an origin. In contrast, hydrogen can be related to extent secondary processes, proportion alkylated within CCs. Here, we experimentally investigate mole...

Context. Among the six atoms of N-containing molecules with formula CH 3 NO, only formamide (H 2 NCHO), most stable structural isomer, has been detected in interstellar medium (ISM). The formaldoxime isomer may be formed, for example, by reaction formaldehyde CO) or methanimine CNH) and hydroxylamine NOH), which are all ISM. lack high accuracy millimeter- submillimeter-wave measurements hinders...

The detection of the 11.3-micron emission feature characteristic Si--C stretch in carbon-rich evolved stars reveals that silicon carbide (SiC) dust grains are condensed outflows carbon stars. SiC could be a significant constituent interstellar since it is generally believed inject considerable amount into medium (ISM). presence ISM also supported by identification presolar stellar origin primit...

The low-temperature rotational (de-) excitation of C3 (X 1 g ) by collisions with He ( S ) is studied using an ab initio potential energy surface (PES). This PES has been calculated using the singleand double-excitation coupledcluster approach with noniterative perturbational treatment of triple excitations [CCSD(T)] and the augmented correlation-consistent triplebasis set (aug-cc-pVTZ) with bo...

Glycolaldehyde is the simplest of the monosaccharide sugars and is directly linked to the origin of life. We report on the detection of glycolaldehyde (CH2OHCHO) towards the hot molecular core G31.41+0.31 through IRAM PdBI observations at 1.4, 2.1, and 2.9 mm. The CH2OHCHO emission comes from the hottest (≥ 300 K) and densest (≥2×10 cm) region closest (≤ 10 AU) to the (proto)stars. The comparis...

This paper presents data from the BIMA interferometer showing spatially resolved absorption spectra of the gravitationally lensed quasar PKS 1830-211. High-resolution (1.2 km s) spectra were taken in two spectral windows centered on the redshifted frequencies of the HCO(2 ← 1) and HCN(2 ← 1) molecular transitions. There is no molecular absorption in the northeast image but the southwest image r...