C. L. Curry

Low upper limits on the O2 abundance from the Odin satellite

For the first time, a search has been conducted in our Galaxy for the 119 GHz transition connecting to the ground state of O2, using the Odin satellite. Equipped with a sensitive 3 mm receiver (Tsy ...

EMBEDDED, SELF-GRAVITATING EQUILIBRIA IN SHEETLIKE AND FILAMENTARY MOLECULAR CLOUDS

Numerical solutions of the isothermal Lane-Emden equation corresponding to self-gravitating gaseous cores embedded within a finite density envelope of overall cylindrical symmetry are presented. These structures may be members of a fragmentation hierarchy proceeding from sheets to filaments to elongated, prolate clumps. The embedded solutions are the first of their kind and, as such, represent a significant improvement on the isolated cloud paradigm used almost exclusively by previous authors. The properties of the equilibria are in reasonable agreement with observations of dense molecular cores in star-forming clouds, despite the fact that there is only one free parameter in the models. We show that this parameter may be identified with the critical wavelength for instability in the parent filament. The implications of further fragmentation and the possible influence of magnetic fields are discussed briefly.

Shapes of Molecular Cloud Cores and the Filamentary Mode of Star Formation

Using recent dust continuum data, we generate the intrinsic ellipticity distribution of dense, starless molecular cloud cores. Under the hypothesis that the cores are all either oblate or prolate randomly oriented spheroids, we show that a satisfactory fit to observations can be obtained with a Gaussian prolate distribution having a mean intrinsic axis ratio of 0.54. Further, we show that correlations exist between the apparent axis ratio and both the peak intensity and total flux density of emission from the cores, the sign of which again favors the prolate hypothesis. The latter result shows that the mass of a given core depends on its intrinsic ellipticity. Monte Carlo simulations are performed to find the best-fit power law of this dependence. Finally, we show how these results are consistent with an evolutionary scenario leading from filamentary parent clouds to increasingly massive, condensed, and roughly spherical embedded cores.

The gas environment of the young stellar object GL 2591 studied by infrared spectroscopy

High-resolution M band (4.6 microns) spectroscopy of GL 2591 is presented. Physical structures noted include an absorption feature with an outflow velocity of about 17 km/s, cold gas (identified with the core of the molecular cloud within which the object is embedded), and very broad C-12O lines formed in a neutral wind. The detection of hot low-velocity gas together with warm high-velocity gas suggests the scenario of a warm neutral wind accelerating from an accretion disk. 32 refs.

First detection of NH3 (10 -g 00) from a low mass cloud core. On the low ammonia abundance of the rho Oph A core

Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of compleme ...