Interstellar Formation Research Articles

Where galaxies collide - II. NGC 5195, the M51 system and the luminosity function of H II regions

We investigate the characteristics of the interstellar medium and massive star formation in the lenticular galaxy NGC 5195 and adjacent and overlying parts of the Whirlpool spiral (M51, NGC 5194) via broad-band red and Hα imaging. Although NGC 5195 has a moderate amount of interstellar gas, we find no visual line emission that is unambiguously associated with star formation in this galaxy. We use our R (0.65 μm) and I (0.8 μm) images to derive a map of the obscuring dust distribution toward this galaxy.

Shock processing of interstellar dust - Diamonds in the sky

view Abstract Citations (111) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Shock Processing of Interstellar Dust: Diamonds in the Sky Tielens, A. G. G. M. ; Seab, C. G. ; Hollenbach, D. J. ; McKee, Christopher F. Abstract The processing of interstellar dust grains by strong shock waves is studied, with the emphasis on the effects of grain-grain collisions. Such collisions provide the high pressures required to transform interstellar graphite and amorphous carbon grains into diamonds. Diamond metamorphism is as important for the destruction of such grains as vaporization and sputtering. It is calculated that about 5 percent of the C is expected to be in the form of 5-100 A diamonds in the interstellar medium. These results support the suggested interstellar origin for the recently discovered small meteoritic diamonds by providing a feasible interstellar formation mechanism. Publication: The Astrophysical Journal Pub Date: August 1987 DOI: 10.1086/184964 Bibcode: 1987ApJ...319L.109T Keywords: Amorphous Materials; Cosmic Dust; Interstellar Matter; Metamorphism (Geology); Meteoritic Diamonds; Shock Waves; Crystal Lattices; Interstellar Gas; Interstellar Magnetic Fields; Phase Transformations; Shock Fronts; Sputtering; Astrophysics; INTERSTELLAR: GRAINS; INTERSTELLAR: MATTER; SHOCK WAVES full text sources ADS |

Stellar spiral arms in smooth-armed galaxies

Deep multicolor surface photometry has been obtained for three extreme examples of smooth-armed spirals, galaxies with a global spiral pattern but with little or no interstellar gas, dust, or recent star formation: NGC 7743, NGC 495 and NGC 718. The results suggest that smooth-armed spirals may be transient bar-driven density waves (with a lifetime of about 1 Gyr) in galaxies which spend most of their lifetimes as much smoother SB0 or SBa galaxies, unless an efficient mechanism for transferring angular momentum from the bar is present. 21 references.

On the contribution of grain surface reactions to interstellar molecule densities

Some recent arguments concerning the relevance of grain surface reactions to interstellar molecule formation are shown to be without foundation. It is probable that surface reactions, gas phase ion-molecule and neutral reactions all contribute to interstellar molecular densities.

Shock-driven implosion of interstellar gas clouds and star formation

Two-dimensional hydrodynamical calculations are presented to demonstrate a mechanism of star formation which, within the context of the spiral density wave theory, can explain the narrowness of the spiral arms of galaxies delineated by the classic spiral tracers: the bright, young stars and their associated H II regions. The implosion of a standard interstellar cloud has been followed numerically after it encounters a shock in the intercloud medium. Parameters have been chosen to represent a cloud flowing into a spiral arm which is delineated by a shock in the interstellar gas. Although this work is motivated by spiral wave theory, the results should also be indicative of the evolution of a cloud struck, for example, by a supernova shock.

Predissociation effects in the A, B, and C states of CH and the interstellar formation rate of CH via inverse predissociation

Predissociation effects in the A, B, and C states of CH and the interstellar formation rate of CH via inverse predissociation