Optical analysis of dust complexes in spiral galaxies

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1979

OSTI ID:5604758

Elmegreen, D A.M.

A method for quantitatively investigating properties of dust regions in external galaxies is presented. The technique involves matching radiative transfer models (with absorption plus scattering) to multicolor photographic and photometric observations. Dust features in each galaxy are modeled with two configurations; one is rectangular with a Gaussian distribution perpendicular to the plane of the galaxy, and the other is a uniform oblate spheroid with an arbitrary height from the midplane. It is found that it is possible to determine the intrinsic opacities in the clouds and in the nearby comparison regions, and that differention between high opacity low-lying clouds and low opacity clouds that are above the midplane can be made. This technique was used to study dust complexes in the late-type spiral galaxies NGC 628 (M74), NGC 5194 (M51), NGC 5457 (M101), and NGC 7793. Most of the features in the prominent dust lanes were found to have internal visual extinctions corresponding to 10 to 15 mag kpc/sup -1/, while the adjacent comparison regions typically contained 4 mag kpc/sup -1/. Thus the opacity through a dust lane is about 1.5 mag greater than the 0.5 to 1.0 mag of extinction through a comparison region. A noticeable deviation from this result was found for all of the dust lanes that occurred on the inner edges of the spiral arm branches. These features had internal densities that were approx. 10 times larger than in their comparison regions, in contrast to the normal dust lanes which had density enhancements of a factor of approx. 3. Dust features which were on the outer sides of spiral arms appeared to be no different than main inner dust lane features.

• Research Organization: Harvard Univ., Boston, MA (USA)
• OSTI ID: 5604758
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION
CONFIGURATION
COSMIC DUST
DUSTS
GALAXIES
MASS
MATHEMATICAL MODELS
OPACITY
OPTICAL PROPERTIES
PHOTOGRAPHY
PHOTOMETRY
PHYSICAL PROPERTIES
SCATTERING
SPIRAL CONFIGURATION