Publication: Automatic selection of new Hα emission-line galaxies using MAMA
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Publication Date
1995-10
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EDP Sciences
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Abstract
A full set of algorithms for the automatic analysis of low-resolution objective-prism spectra has been developed with the aim of finding new emission-line galaxies (ELGs) candidates from the Universidad Complutense de Madrid (UCM) survey prism plates. An objective-prism plate and a direct plate, used for pairing objects and to perform star-galaxy separation, have been scanned with the MAMA machine. The plates were taken in the red region of the spectrum, using the Hα+[NII] blend in emission as selection criterion. The procedure, applied to digitized spectra, is able to automatically select ELGs candidates. Density to intensity transformation has not been used in our method; the detection of the emission is performed applying three independent criteria over the one-dimensional spectra in raw data. The automatically selected sample is compared with that obtained after a careful visual scan. Spectroscopic observations at moderate spectral resolution are presented for the whole sample of candidates in order to study the drawbacks and the biases of both methods.
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© ESO 1995. We would like to gratefully acknowledge the friendly assistance and warm hospitality received from the MAMA staff, and especially from Dr. Jean Guibert. We also express our thanks to the Calar Alto Obvservatory staff for their inestimable observing support, to M. Cordero, J. Gorgas and S. Pedraz for the first spectroscopic observations of candidates and to A.G. Vitores for useful suggestions and careful review of this paper. This work is based on observations collected at the German-Spanish Astronomical Center, Calar Alto, Spain, operated by the Max-Planck-Institut für Astronomie (MPIA), Heidelber, jointly with the Spanish National Commission for Astronomy, and with the Isaac Newton Telescope, operated by the Royal Greenwich Observatory at the Spanish Observatory Roque de los Muchachos of the Instituto de Astrofísica de Canarias on behalf of the Science and Engineering Research Council of the United Kingdom and the Netherland Organization for Scientific Research. This work has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the JET Propulsion Laboratory, Caltech, under contract with the National Aeronautics and Space Administation. This work was suppported in part by the Spanish “Programa Sectorial de Promoción del Conocimiento” under grant PB93-456.