Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...280..373b&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 280, no. 2, p. 373-382
Astronomy and Astrophysics
Astrophysics
31
Diameters, H Ii Regions, Luminosity, Position (Location), Spiral Galaxies, Data Reduction, H Alpha Line, Interstellar Matter, Magnitude
Scientific paper
For a sample of 22 spiral galaxies, most of which are in Virgo, we measure positions, diameters and relative magnitudes of the H II regions. The diameter frequency integral distribution is found to follow the exponential law proposed by van den Bergh (1981) with no exceptions. The scale diameter, D0, (1) depends on the galactic absolute magnitude with the law log(D0) = -0.123 +/- 0.007 MB -0.33 +/- 0.14, (2) has a tendency to be larger at the periphery than in the inner part of the galaxy and (3) is systematically larger along the arms than inter-arms. Although with a large dispersion, a cubic relationship between H II region luminosity and diameter, consistent with a radiation bounded geometry, is found for each galaxy. The differential luminosity function distribution is described by a power law with index in the range (1.3 less than or equal to alpha less than or equal to 2.4) and a mean index mean value of alpha = 1.8 +/- 0.3 in agreement with previous works. The index alpha is found to depend on the morphological type of the galaxy being steeper for early than late-type spirals. It sensibly changes if arm and inter-arm distributions are separately considered, but does not depend on the galactocentric distance. The environment characterized by the local density of galaxies does not seem to play a role in the shape of the LF while the diameter scale of H II regions seems to be well defined in a narrow region of values at densities rho greater than or equal 1.2 (galaxies/cubic Mpc) while at lower density the scale diameter shows large fluctuations.
Banfi M.
Chincarini Guido
Henry Richard B. C.
Rampazzo Roberto
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