We have observed CO J = 2 → 1 and J = 1 → 0, and CO J = 1 → 0 emission in two regions of HI Self-Absorption (HISA) in Perseus: a small, isolated HISA feature called the globule and a more extended HISA cloud called the complex. Using both Large Velocity Gradient and Monte Carlo radiative transfer codes we found that, in the globule, N(CO) < 6.0 × 10 cm which, using PDR models, implies that N(H2...

We have used archival far-ultraviolet spectra from observations made by the Space Telescope Imaging Spectrograph (STIS) of the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer (FUSE ) to determine the column densities and rotational excitation temperatures for carbon monoxide and molecular hydrogen, respectively, along the lines of sight to 23 Galactic O and B stars. The si...

We report high spatial resolution VLA observations of the low-mass starforming region IRAS 16293-2422 using four molecular probes: ethyl cyanide (CH3CH2CN), methyl formate (CH3OCHO), formic acid (HCOOH), and the ground vibrational state of silicon monoxide (SiO). Ethyl cyanide emission has a spatial scale of ∼20 and encompasses binary cores A and B as determined by continuum emission peaks. Sur...

Recent studies of nearby spiral galaxies suggest that photodissociation regions (PDRs) are capable of producing much of the observed HI in galaxy disks. In that case, measurements of the observed HI column density and the far–ultraviolet (FUV) photon flux responsible for the photodissociation process provide a new probe of the volume density of the local underlying molecular hydrogen. We develo...

We present observations of H2 fluorescence at wavelengths between 1000 and 1200 Å from the bright reflection nebula IC 63. Observations were performed with the Berkeley spectrograph aboard the ORFEUS-II mission (Hurwitz et al. 1998). To the best of our knowledge, this is the first detection of astrophysical H2 fluorescent emission at these wavelengths (excluding planetary atmospheres). The shap...

Ultraviolet photolysis of various coronene-ice mixtures at low temperature and pressure caused the addition of amino (”NH2), methyl (”CH3), methoxy (”OCH3), cyano/isocyano (”CN, ”NC), and acid (”COOH) functional groups to the polycyclic aromatic hydrocarbon (PAH) coronene (C24H12), in addition to previously reported alcohol (”OH) and ketone (>C»O) formation. This work represents the first exper...

We have searched for OH absorption against seven pulsars using the Arecibo telescope. In both OH mainlines (at 1665 and 1667 MHz), deep and narrow absorption features were detected toward PSR B1849+00. In addition, we have detected several absorption and emission features against B33.6+0.1, a nearby supernova remnant (SNR). The most interesting result of this study is that a pencil-sharp absorp...

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...

We present our diagnosis of the role massive stars play in the formation of lowand intermediate-mass stars in OB associations. In the bright-rimmed and comet-shaped clouds in both the OriOB1 and LacOB1 associations, there is compelling evidence of lowand intermediate-mass star formation dominated by the triggering process by the massive stars in the regions. The expanding ionization fronts from...

Quartic force fields for the ground electronic states of the most stable C4 radical isomers [l-C4(X 3 g ) and r-C4(X Ag)] are computed at the same level of theory. These computations are performed using interaction configuration ab initiomethods and the cc-pVTZ basis set. These force fields on symmetry-adapted coordinates are derived from full six-dimensional potential energy surfaces generated...