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We verify whether the O/H abundances of galaxies can be derived from the equivalent width (EW) R23 instead of the extinction-corrected flux R23, and eventually propose a method of improving the reliability of this empirical method, which is often used for the non-flux calibrated spectra of galaxies. We select 37,173 star-forming galaxies from the SDSS-DR2, which offers a wide range of properties to test the EW method. The EW-R23 method brings with it a significant bias: for the bulk of SDSS galaxies, it may affect the determination of log(O/H) by factors ranging from -0.2 to 0.1 dex and for some galaxies by factors ranging from -0.5 to 0.2 dex. We characterize this discrepancy (or bias) by alpha = (I_[OII]/I_Hbeta)/(EW_[OII]/EW_Hbeta), which is virtually independent of dust extinction, while tightly correlating with Dn(4000), although at a lower significance, with (g-r) colors. The EW-R23 method cannot be used as a proxy for the extinction-corrected flux R23 method. From analytical third-order polynomial fits of alpha versus (g-r) colors, we have been able to correct the EW-R23 method. With this additional and easy correction, the EW-R23 method provides O/H abundance values similar to those derived from the extinction-corrected flux R23 method with an accuracy of ~0.1 dex for >92% of the SDSS galaxies.
We present a tool for measuring the equivalent width (EW) in high-resolution spectra. The Tool for Automatic Measurement of Equivalent width (TAME)provides the EWs of spectral lines by profile fitting in the automatic or the interactive mode, which c
Our understanding of stars through asteroseismic data analysis is limited by our ability to take advantage of the huge amount of observed stars provided by space missions such as CoRoT, Kepler, K2, and soon TESS and PLATO. Global seismic pipelines pr
Internet supercomputing is an approach to solving partitionable, computation-intensive problems by harnessing the power of a vast number of interconnected computers. For the problem of using network supercomputing to perform a large collection of ind
[Abridged] We investigate the frequency of the various spectral types as a function both of the clusters properties and of the galaxies characteristics. In this way, using the same classification criteria adopted for higher redshift studies, we can c
We quantify the distribution of [OIII]+H$beta$ line strengths at z$simeq$7 using a sample of 20 bright (M$_{mathrm{UV}}$ $lesssim$ $-$21) galaxies. We select these systems over wide-area fields (2.3 deg$^2$ total) using a new colour-selection which p