Nature of luminous IRAS galaxies

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5582157

DePoy, D L

A flux-limited sample of 23 optically identified galaxies was selected from Infrared Astronomical Satellite (IRAS) data that have far-infrared luminosities greater than {approximately}5 {times} 10{sup 10} solar luminosities, substantially larger than those of normal spiral galaxies. If star formation is the cause of the large luminosities, then strong hydrogen recombination-line emission should be present, although substantial extinction is probable. Accordingly, the sample was observed for Br{alpha} (n = 5 {yields} 4) hydrogen recombination line emission; 15 of the galaxies have had Br{gamma} (n = 7 {yields} 4) line measurements. Sixteen of the sample galaxies were detected in one or both of the lines. Additional infrared photometry and silicate optical-depth measurements were used along with measured line ratios to correct the observed line strengths for the effects of extinction and spatially-extended emission. Most of the galaxies have line strengths that can be adequately explained by recombination of hydrogen ionized by the continuum radiation from high-mass stars. In particular, the ratio of the galaxies' luminosity to the estimated number of ionizing continuum photons is what would be expected from a burst of star formation. There are several galaxies that have weak lines and very few ionizing continuum photons for their luminosities.

• Research Organization: Hawaii Univ., Honolulu, HI (USA)
• OSTI ID: 5582157
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION SPECTRA
GALAXIES
HYDROGEN
INFRARED RADIATION
IONIZATION
LUMINOSITY
NONMETALS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
RECOMBINATION
SPECTRA
STAR EVOLUTION