Statistics – Computation
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...429..572s&link_type=abstract
The Astrophysical Journal, vol. 429, no. 2, pt. 1, p. 572-581
Statistics
Computation
153
Abundance, Chemical Composition, Evolution (Development), Galactic Evolution, Metallicity, Optical Properties, Seyfert Galaxies, Spectral Energy Distribution, Star Formation Rate, Starburst Galaxies, Computation, Light (Visible Radiation), Near Infrared Radiation, Observatories, Photometry, Ultraviolet Radiation
Scientific paper
Spectral distributions from the UV to the near-IR of a sample of 44 star-forming galaxies are used to calculate the metallicity (O/H), star-formation rate (SFR) and age of the starbursts. The oxygen abundance covers the range 8.3 less than O/H less than 9.4 and nitrogen (N) is found to be mostly a product of secondary nucleosynthesis for O/H greater than 8.4. Due to its secondary origin, N/O ratios up to approximately equals 4 times the solar value can be obtained for metal-rich starbursts. The SFR ranges 0.01 to 100 solar mass/year. The lower metallicity galaxies seem to be experiencing an instantaneous burst of star formation, with ages ranging from under 5 x 106 to 107 yr. The highest metallicity galaxies are most probably experiencing a continuous burst. Correlations between the calculated quantities and several spectral features are investigated. We found a highly significant correlation between the equivalent width W(C IV lambda 1550)-a stellar (absorption) feature- and the oxygen abundance of the emitting gas (O/H). Thus we show for the first time that the stellar metallicity is well correlated with the gas metallicity in star-bursting galaxies. The equivalent width W(Si IV lambda 1400) and the emission line ratio (N II) lambda lambda 6548.84/Halpha also correlate well with O/H, and all three features can be used as metallicity indicators for star-forming galaxies. The continuum color between lambda 1400 and lambda 3500 (C(14 - 35)) is shown to correlate with O/H, although it is better correlated with E(B - V). It was not possible to disentangle the metallicity from the reddening effect in C(14- 35). We estimate that the reddening affecting the UV continuum is about half the one derived from the Balmer decrement of the emitting gas. The SFR correlates well with the galaxy luminosity and there is no dependence of the continuum color on the SFR. The higher metallicities are only found in the more luminous galaxies, while low metallicities are found over the whole luminosity interval (-16 less than MB less than -23, H0 = 50 km/sec/Mpc) covered by the sample.
Calzetti Daniela
Kinney Anne L.
Storchi-Bergmann Thaisa
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