The stellar content of the nuclear regions of Sc galaxies

• Main Author: Turnrose, Barry Edmund
• Format: Others
• Published: 1976
• Online Access: https://thesis.library.caltech.edu/3414/1/Turnrose_be_1976.pdf; Turnrose, Barry Edmund (1976) The stellar content of the nuclear regions of Sc galaxies. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/4HGY-GB71. https://resolver.caltech.edu/CaltechETD:etd-09092008-130914 <https://resolver.caltech.edu/CaltechETD:etd-09092008-130914>

<p>The stellar content of the nuclear regions of seven nearby Sc galaxies has been determined by means of population syntheses utilizing narrow-band spectrophotometric observations covering the wavelength range 3300Å-10400Å. A linear-programming fitting technique is used in conjunction with simple models of star formation to provide physically consistent population models incorporating multiple generations of stars. Evidence is found for substantial intrinsic reddening in the nuclear regions studied. Upper main-sequence stars are significant contributors in most cases, and the lower main sequence contributes insignificantly in all cases. All available indicators are consistent with M-giant-star dominance at the longest wavelengths.</p> <p>Absolute measurements of the emission-line spectra of the nuclear regions are presented and discussed. The 0-B stars arising naturally in the population models are found to be just sufficient to provide the observed nuclear ionization in all cases but NGC 5194, which may be collisionally ionized. The observed stellar populations are largely consistent with simple evolutionary models of star formation using a "local" initial mass function and a variety of time dependences ranging from exponential decays with time constants ~3-6 billion years to constant rates. A possibly significant correlation between stellar content and dynamical properties among four of the program galaxies is pointed out.</p>