Interstellar formaldehyde

Abstract: OBSERVATIONS over the infrared waveband 2–30 µm available for a number of astronomical objects are shown here to be reconcilable with the transmittance properties of polysaccha-rides. Using an experimentally determined transmittance spectrum for cellulose we can readily relate astronomical data in the 2–4-µm, 8–13-µm and 15–30-µm wavebands and we obtain close fits to astronomical spectra in these several bands. From this detailed spectral agreement we consider it reasonable to infer the detection of interstellar polysaccharides. The identification of this highly complex macromolecule, presumably formed by an abiogenic processing of interstellar formaldehyde, could have a profound bearing on interstellar chemistry including the evolution of prebiotic molecules.

Abstract: Water is an important reservoir species for oxygen in interstellar space and plays a key role in the physics of star formation through cooling by far-infrared emission. While water vapor is present...

Abstract: Upper limits to the strength of the HDCO (1$sub 11$-1$sub 10$) transition at 5346 MHz are obtained from observations of Cas A, Cloud 4, NGC 2264, DR 21, Orion B, and Sgr B2. The observations are interpreted to yield an upper limit to the abundance ratio HDCO/H$sub 2$CO that is most likely)about 1/ 170. We show that likely pure gas-phase processes (those employing CH$sub 3$+O and CH$sub 3$$sup +$+O) which have been proposed to form interstellar formaldehyde must also produce an enhanced HDCO/H$sub 2$CO ratio. Our observations indicate that the required enhancement probably does not occur. Formaldehyde is observed widely throughout the Galaxy and apparently requires a more complicated formation process than the simplest molecules. If gas reactions to produce formaldehyde cannot be found, it seems unlikely that the more complex interstellar molecules are produced purely by gas-phase reactions under the low temperature-density conditions where they are observed. (AIP)