Spectrophotometric properties of galaxies at intermediate redshifts (z ~ 0.2--1.0) I. Sample description, photometric properties and spectral measurements

Abstract

We present the spectrophotometric properties of a sample of 141 emission-line galaxies at redshifts in the range $0.2<z<1.0$ with a peak around $z\in [0.2,0.4]$. The analysis is based on medium resolution ($R\_\mathrm{s}=500-600$), optical spectra obtained at VLT and Keck. The targets are mostly {} "Canada-France Redshift Survey" emission-line galaxies, with the addition of field galaxies randomly selected behind lensing clusters. We complement this sample with galaxy spectra from the {} "Gemini Deep Deep Survey" public data release. We have computed absolute magnitudes of the galaxies and measured the line fluxes and equivalent widths of the main emission/absorption lines. The last two have been measured after careful subtraction of the fitted stellar continuum using the \texttt{platefit} software originally developed for the SDSS and adapted to our data. We present a careful comparison of this software with the results of manual measurements. The pipeline has also been tested on lower resolution spectra, typical of the {} "VIMOS/VLT Deep Survey" ($R\_\mathrm{s}=250$), by resampling our medium resolution spectra. We show that we can successfully deblend the most important strong emission lines. These data are primarily used to perform a spectral classification of the galaxies in order to distinguish star-forming galaxies from AGNs. Among the initial sample of 141 emission-line galaxies, we find 7 Seyfert 2 (narrow-line AGN), 115 star-forming galaxies and 16 {} "candidate" star-forming galaxies. Scientific analysis of these data, in terms of chemical abundances, stellar populations, etc, will be presented in subsequent papers of this serie.

24 pages. Accepted for publication in A&A; reference added; bug corrected: flux scaled by (1+z)