Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...281...26k&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 281, no. 1, p. 26-34
Astronomy and Astrophysics
Astrophysics
32
Abundance, Astronomical Models, Galactic Evolution, Gas Flow, Gradients, Spiral Galaxies, Interstellar Matter, Mass Distribution, Mathematical Models, Metallicity, Star Formation, Velocity Distribution
Scientific paper
The temporal evolution of abundance gradients in the disks of galaxies is computed assuming gas infall and radial gas flows. Analytical and numerical models show: The intial value of the gradient is determined by radial variations of the metal yield and the star formation timescale, and the dependence of the star formation rate on gas density. This gradient may be modified by the action of radial gas flows, if the infall occurs slower than the typical star formation timescale. Depending on the velocity field, the gradient can be steepened or flattened both by ionflows or outflows Comparison with observational data of the Galaxy shows: The existence of steep present abundance gradients (seen with HII regions and planetary nebulae) and the absence of metallicity gradients in old disk stars and disk globular clusters implies that the yield should not have a radial variation and the star formation should depend fairly linearly on the gas density. Radial gas flows towards the galactic center can account for the presently available data, if they have a velocity in the solar vicinity of about 1 km/s, increasing with galactocentric distance.
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