Massive star formation in Wolf-Rayet galaxies - V. Star-formation rates, masses and the importance of galaxy interactions

摘要

Aims. We performed a comprehensive analysis of asample of 20 starburst galaxies that show a substantial population ofvery young massive stars, most of them classified as Wolf-Rayetgalaxies. Methods. In this paper, the last in the series, weanalyze the global properties of our galaxy sample usingmultiwavelength data extracted from our own observations (Hfluxes, B and H-bandmagnitudes) and from the literature, which include X-ray, FUV, FIR, andradio (both HIspectralline and 1.4GHz radio-continuum) measurements. Results. The agreement between our H-basedstar-formation rates (S FR) and thoseprovided by indicators at other wavelengths is remarkable, but weconsider that the new H-basedcalibration provided by Calzetti etal. (2007, ApJ, 666, 870)should be preferred to older calibrations. The FUV-based S FRprovides a powerful tool for analyzing the star-formation activity onboth global and local scales independently to the Hemission. We provide empirical relationships between the ionized gasmass, neutral gas mass, dust mass, stellar mass, and dynamical masswith the B-luminosity. Although all massestimations increase with increasing luminosity, we find importantdeviations to the general trend in some objects, which seem to be theconsequence of their particular evolutionary histories. The analysis ofthe mass-to-light ratios give similar results. We investigate themass-metallicity relations and conclude that both the nature and thestar-formation history are needed to understand the relationshipsbetween both properties. The majority of the galaxies follow aSchmidt-Kennicutt scaling law of star-formation that agrees with thatreported in individual star-forming regions within M51 butnot with that found in normal spiral galaxies. Dwarf galaxies seem tobe forming stars more efficiently than the outskirts of spiralgalaxies. We find a relation between the reddening coefficient and thewarm dust mass indicating that the extinction is mainly internal to thegalaxies. The comparison with the closed-box model also indicates thatthe environment has strongly affected their evolution. Conclusions. Considering all multiwavelength data,we found that 17 up to 20 galaxies are clearly interacting or mergingwith low-luminosity dwarf objects or HIclouds.The remaining three galaxies (Mkn5, SBS1054+364,and SBS1415+437) show considerable divergences of someproperties when comparing with similar objects. Many of theinteracting/merging features are only detected when deep opticalspectroscopy and a detailed multiwavelength analysis, includingHIobservations, areobtained. We conclude that interactions do play a fundamental role inthe triggering mechanism of the strong star-formation activity observedin dwarf starburst galaxies. Key words: galaxies: starburst - galaxies:interactions - galaxies: dwarf - galaxies: abundances - stars:Wolf-Rayet - galaxies: kinematics and dynamics