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The stellar content of the nuclear regions of Sc galaxies


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.


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.

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.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:astronomy ; Sc galaxies
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astronomy
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Oke, J. Beverley
Group:Astronomy Department
Thesis Committee:
  • Oke, J. Beverly (chair)
  • Franklin, Joel N.
  • Münch, Guido
  • Toomre, Alar
Defense Date:30 July 1975
Non-Caltech Author Email:turnrose (AT)
Record Number:CaltechETD:etd-09092008-130914
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3414
Deposited By: Imported from ETD-db
Deposited On:17 Sep 2008
Last Modified:21 Dec 2019 04:52

Thesis Files

PDF (Turnrose_be_1976.pdf) - Final Version
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