|Merged catalogue of reflection nebulae|
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/141
|Infrared Emission from Interstellar Dust. III. The Small Magellanic Cloud|
The infrared emission from interstellar dust in the Small MagellanicCloud is modeled using a mixture of amorphous silicate and carbonaceousgrains, including a population of polycyclic aromatic hydrocarbon (PAH)molecules. We show the following: (1) This dust model is able toreproduce the spectral energy distribution from near-IR to far-IR forthe entire SMC Bar region, provided that the PAH abundance in the SMCBar region is very low. (2) The IR spectrum of the SMC B1 No. 1molecular cloud can also be reproduced by our dust model, provided thatthe PAH abundance is increased relative to the overall SMC Bar. The PAHsin SMC B1 No. 1 incorporate ~3% of the SMC C abundance, compared to lessthan 0.4% in the SMC Bar. (3) The spectrum of SMC B1 No. 1 is bestreproduced if the PAH mixture has intrinsic IR band strengths thatdiffer from the band strengths that best fit Milky Way PAH mixtures. Thevariation in the PAH IR band strengths would imply different PAHmixtures, presumably a consequence of differing metallicity orenvironmental conditions. Other possibilities such as superhydrogenationof PAHs and softening of the starlight spectrum are also discussed.
|A survey of [HDCO]/[H2CO] and [DCN]/[HCN] ratios towards low-mass protostellar cores|
We present observations of [HDCO]/[H2CO] and [DCN]/[HCN]ratios towards a selection of low-mass protostellar cores in threedifferent star forming regions. The best fit to the observed[HDCO]/[H2CO] ratios is ~ 0.05-0.07, similar to the valuesobserved towards the dark clouds, TMC-1 and L134N. [DCN]/[HCN] ratiosare ~ 0.04, higher than those seen in TMC-1, around the low-massprotostar IRAS 16293 and the Orion Hot Core, but similar values to theOrion Compact Ridge and L134N. We compare our results with predictionsfrom detailed, chemical models, and to other observations made in thesesources. We find best agreement between models and observations byassuming that interaction between gas phase molecules and dust grainshas impacted on the chemistry during the cold pre-collapse phase of thecloud's history. The abundance of deuterated species indicates that thedense gas out of which a low mass protostar forms, evolves and collapseson a timescale of <=50 000 years. We find no marked differencebetween molecular D/H ratios towards different regions, or between Class0 and Class I protostars. However, the striking difference between the[DCN]/[HCN] ratios we have measured and those previously observedtowards Hot Molecular Cores leads us to suggest that there aresignificant evolutionary differences between high and low mass starforming regions.
|Physical properties of 90 AU to 250 AU pre-main-sequence binaries.|
|Briefly noted: Irish astronomy (poem)|
|A catalogue of bright nebulosities in opaque dust clouds|
Abstract image available at:http://adsabs.harvard.edu/abs/1977A&AS...29...65B
|Untersuchungen über Reflexionsnebel am Palomar Sky Survey I. Verzeichnis von Reflexionsnebeln|
|Faint Halpha-emission star near rho Ophiuchi and sigma Scorpii.|
|TThe source of luminosity in galactic nebulae.|
|A general study of diffuse galactic nebulae.|
|On a great nebulous region and the question of absorbing matter in space and the transparency of the nebulae.|