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Дата изменения: Thu Sep 27 10:02:18 2012 Дата индексирования: Wed Jan 30 03:03:18 2013 Кодировка: Поисковые слова: neutron |
Abstract
A model
for the chemical evolution of a disk galaxy is presented. The model reproduces
all the basic
parameters of our own Galaxy, including, for the first time, the correlation
between metallicity and height above
the Galactic plane. One version of this model had been used earlier to
study the effect of heavy element loss
from spiral galaxies on the chemical evolution of the intergalactic medium.
Here, the primary emphasis is on
investigations of the star formation history. Varying the basic parameters
of the model -- the mass and radius of
the galaxyЫand incorporating a delay in the onset of star formation make
it possible to model different scenar-
ios for the evolution of a galaxy's luminosity. There is a phase of enhanced
star formation in the early stages of
evolution of massive galaxies. Taking into account the absorption of optical
radiation by dust grains makes
it possible to explain certain observed characteristics of the luminosity
evolution, in particular, the absence
of bursts in optical luminosity in disk galaxies at the initial period
of intense star formation. The possibility
of reconstructing the star-formation history and galactic luminosity from
observations of galaxies at different
redshifts z is discussed. If selection effects are accurately taken
into account, the model makes it possible to
construct specific evolutionary scenarios that are consistent with the
observations. Factors responsible for the
deviation of the evolution of the average luminosity from the luminosity
history in individual galaxies are
discussed.