K. Lehtinen

Molecular Abundance Enhancements in the Highly Collimated Bipolar Outflow BHR 71

We report observations of the J = 3 → 2 and J = 2 → 1 transitions of SiO and CS, the Jk = 3k → 2k and Jk = 2k → 1k transitions of CH3OH, and the J = 1 → 0 transition of HCO+, made with Swedish-ESO Submillimetre Telescope (SEST), toward the highly collimated bipolar outflow BHR 71. Broad wing emission was detected toward the outflow lobes in all the observed molecular lines. The shapes of the profiles are strikingly different from molecule to molecule. For CS and HCO+ the emission from the outflowing gas appears as a weak broad feature superposed upon a strong narrow emission from the quiescent ambient gas. For CH3OH the intensity of the broad emission feature is considerably stronger than that of the narrow component, whereas for SiO the broad feature completely dominates the emission spectra. The spatial distribution of the integrated wing emission is considerably extended and broadly similar in all the observed molecular transitions, showing well-separated blueshifted and redshifted lobes with FWHM angular sizes of 24 × 13 and 24 × 14, respectively. We find that the abundance of methanol and silicon monoxide in the outflow lobes is enhanced with respect to that of the ambient cloud by factors of up to ~40 and 350, respectively. The large enhancements of methanol and silicon monoxide in the outflow lobes are most likely due to the release from grains of ice mantles and Si-bearing species via shocks produced by the interaction between the outflow and dense ambient gas. On the other hand, we find that the abundance of HCO+ in the outflowing gas is smaller than that in the ambient gas by about a factor of 20, a decrease consistent with theoretical predictions of shock models.

Far-infrared and molecular line observations of Lynds 183 – Studies of cold gas and dust

We have mapped the dark cloud L183 in the far-infrared at 100 m and 200 m with the ISOPHOT photometer aboard the ISO satellite. The observations make it possible for the rst time to study the distribution and properties of the large dust grains in L183 without confusion from smaller grains. The observations show clear colour temperature variations which are likely to be caused by changes in the emission properties of the dust particles. In the cloud core the far-infrared colour temperature drops below 12 K. The data allow a new determination of the cloud mass and the mass distribution based on dust emission. The estimated mass within ar adius of 10 0 from the cloud centre is 25M. We have mapped the cloud in several molecular lines including DCO+(2{1) and H 13 CO+(1{0). These species are believed to be tracers of cold and dense molecular material and we detect a strong anticorrelation between the DCO+ emission and the dust colour temperatures. In particular, the DCO+(2{1) emission is not detected towards the maximum of the 100 m emission where the colour temperature rises above 15 K. The H 13 CO+ emission follows closely the DCO+ distribution but CO isotopes show strong emission even towards the 100m peak. Detailed comparison of the DCO+ and C 18 O maps shows sharp variations in the relative intensities of the species. Morphologically the 200 m dust emission traces the distribution of dense molecular material as seen e.g. in C 18 O lines. A comparison with dust column density shows, however, that C 18 O is depleted by a factor of1.5 in the cloud core. We present results of R -a ndB-band starcounts. The extinction is much better correlated with the 200 mt han with the 100m emission. Based on the 200m correlation at low extinction values we deduce a value of 17 m for the visual extinction towards the cloud centre where no background stars are observed anymore.

Unidentified infrared bands in the interstellar medium across the Galaxy

We present a set of 6–12

Detection of 6 K gas in Ophiuchus D

\rm{\mu m}

The ratio of N(C

ISOPHOT-S spectra of the general interstellar medium of the Milky Way. This part of the spectrum is dominated by a series of strong, wide emission features commonly called the Unidentified Infrared Bands. The sampled area covers the inner Milky Way from l = -60°to +60° with a ten-degree step in longitude and nominal latitudes b = 0°, ± 1°. For each grid position the actual observed direction was selected from IRAS 100

\mathsf{^{18}}

\rm{\mu m}

O) and A

maps to minimize contamination by point sources and molecular clouds. All spectra were found to display the same spectral features. Band ratios are independent of band strength and Galactic coordinates. A comparison of total observed flux in band features and IRAS 100

\mathsf{_{V}}

\rm{\mu m}

in Chamaeleon I and III-B - Using 2MASS and SEST

emission, a tracer for large interstellar dust grains, shows high correlation at large as well as small (1´) scales. This implies a strong connection between large dust grains and the elusive band carriers; the evolutionary history and heating energy source of these populations must be strongly linked. The average mid-infrared spectrum of the Milky Way is found to be GROUP the average spectrum of spiral galaxy NGC 891 GROUP The common spectrum can therefore be used as a template for the 6–12

The relationship of CO abundance to extinction and N(H

\rm{\mu m}