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For refcode 1993A&A...280..373B:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1993A&A...280..373B H II regions in spiral galaxies: positions, luminosity function and diameter distribution M. Banfi, R. Rampazzo, G. Chincarini, and R.B.C. Henry Dipartimento di Fisica, Universita degli Studi di Milano, Via Celoria 16,1-20100 Milano, Italy Osservatorio Astronomico di Brera, Via Brera 28,1-20121 Milano, Italy University of Oklahoma, Dept. of Physics, Norman, Oklahoma USA Received January l9, accepted June 13,1993 Abstract. 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, D_0_, 1) depends on the galactic absolute magnitude with the law log(D_0_) = -0.1231+/-0.007 M_B_ -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 <= {alpha} <= 2.4) and a mean index <{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 Il regions seems to be well defined in a narrow region of values at densities {rho} >= 1.2 (galaxies Mpc^-3^) while at lower density the scale diameter shows large fluctuations. Key words: galaxies: spiral - galaxies: interstellar matter - interstellar medium: H II regions
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