Sally W. Stemwedel

COBE diffuse infrared background experiment observations of the galactic bulge

Low angular resolution maps of the Galactic bulge at 1.25, 2.2, 3.5, and 4.9 micrometers obtained by the Diffuse Infrared Background Experiment (DIRBE) onboard NASAs Cosmic Background Explorer (COBE) are presented. After correction for extinction and subtraction of an empirical model for the Galactic disk, the surface brightness distribution of the bulge resembles a flattened ellipse with a minor-to-major axis ratio of approximately 0.6. The bulge minor axis scale height is found to be 2.1 deg +/- 0.2 deg for all four near-infrared wavelengths. Asymmetries in the longitudinal distribution of bulge brightness contours are qualitatively consistent with those expected for a triaxial bar with its near end in the first Galactic quadrant (0 deg less than l less than 90 deg). There is no evidence for an out-of-plane tilt of such a bar.

The unusual cometary star-forming region G110-13

We present far-IR, radio continuum, and spectral line observations of an unusual, highly elongated, comet-shaped molecular cloud, located about 100 pc from the Galactic plane. The presence of three late B-type stars embedded within, or adjacent to, this low-mass cloud implies a star-forming efficiency that may be as high as 30 percent. Several mechanisms that may have been responsible for its unusual morphology and high star-forming efficiency will be described and evaluated. Although ram-pressure resulting from the rapid motion of this cloud through the interstellar medium could explain its streamlined appearance, there is evidence that G110-13 is the compression front formed by a recent cloud collision.

Equilibrium models of self-gravitating inviscid disks resulting from the collapse of rotating clouds

A method is presented for the construction of velocity and surface density profiles of infinitely thin, self-gravitating disks formed from the collapse of spherical clouds, under the condition that the angular momentum of each material parcel is conserved. Results are presented for initially uniformly rotating clouds with density distributions varying as R exp -n and n = 0, 1, 2. The resulting disk surface density distributions are well represented by power laws in the cylindrical radius over most of their extent. The form of the zeroth-order approximation provides a useful representation of the final surface density function near the center for all three cases, and for n = 2 this result holds throughout the disk. This result is not generally true for the velocity functions, however. 35 refs.

Infrared point source photometry with DIRBE: Instrument gain stabilization and variable star monitoring

The COBE/DIRBE data archive contains a unique record of bright IR point source observations over the entire sky. This paper reviews the method by which point source photometry is calculated from the DIRBE time‐ordered sky survey data. Also shown are some examples of how this point source photometry is being used to calibrate the gain of the DIRBE photometric system, monitor variable stars, and measure stellar polarization.

Observations of the large-scale infrared emission from the galactic plane region by the diffuse infrared background experiment

The Diffuse Infrared Background Experiment (DIRBE) on board NASAs Cosmic Background Explorer (COBE) satellite has surveyed the entire sky in 10 broad photometric bands covering the wavelength region from 1 to 240 micrometers , at an angular resolution of 0.7 degree(s) (Boggess et al. 1992). the extensive spectral coverage of the DIRBE observations offers an unprecedented opportunity to undertake comprehensive large-scale studies of the content, structure, and energetics of the stellar and interstellar components of the Galaxy. Understanding the Galactic emission is not only a task of scientific value in its own right, but also a necessary step in the accurate extraction of faint cosmological emission from the DIRBE data.