Astronomy and Astrophysics – Astrophysics
Scientific paper
Nov 1985
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985a%26a...152..427c&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 152, no. 2, Nov. 1985, p. 427-433. FINEP-CNPq-supported research.
Astronomy and Astrophysics
Astrophysics
38
H Ii Regions, Interstellar Matter, Magellanic Clouds, Spiral Galaxies, Chronology, Collapse, Mass Distribution, Stellar Evolution
Scientific paper
The H II region evolutive models of Copetti et al. (1984) were compared with observational data of H II regions in the Magellanic Clouds, M33, M101 and of "isolated extragalactic H II regions". The main results are (1) IMF with χ = 3 or 2.5 are inconsistent with a large number of H II regions; (2) The more uniform age distribution of isolated extragalactic H II regions obtained through an IMF with χ = 2 suggests that this value is more realistic than χ = 1 or 1.5; (3) The H II region age estimates indicate a burst of star formation about 5.5±1.0×106yr ago in the LMC and about 2.3±0.9×106yr ago in the SMC; (4) The observed [O III]/Hβ gradient in M33 and M101 must be caused by color temperature variation of the radiation ionizing the H II regions; (5) Although the variations of WHβ and [O III]/Hβ may be explained qualitatively by metallicity gradients in M33 and M101, the values are only compatible with evolved H II regions with ages between 2 and 5×106yr.
Copetti Marcus V. F.
Dottori Horácio Alberto
Pastoriza Miriani Griselda
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