ESO Imaging Survey

Free access article

Issue		A&A Volume 384, Number 1, March II 2002


Page(s)		81 - 98
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20020007

A&A 384, 81-98 (2002)
DOI: 10.1051/0004-6361:20020007

Exploring the optical/infrared imaging data of CDF-S: Point sources

E. Hatziminaoglou¹, M. A. T. Groenewegen¹, L. da Costa¹, S. Arnouts¹, C. Benoist², R. Madejsky^{1, 3}, R. P. Mignani¹, L. F. Olsen⁴, C. Rité^{1, 5}, M. Schirmer⁶, R. Slijkhuis¹ and B. Vandame¹

¹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching b. München, Germany
² Observatoire de la Côte d'Azur, BP 229, 06304 Nice Cedex 4, France
³ Universidade Estadual de Feira de Santana, Campus Universitário, Feira de Santana, BA, Brazil
⁴ Astronomical Observatory, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
⁵ Observatório Nacional, Rua Gen. José Cristino 77, Rio de Janerio R.J., Brazil
⁶ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching b. München, Germany

(Received 16 August 2001 / Accepted 20 December 2001 )

Abstract
This paper describes the methodology currently being implemented in the EIS pipeline for analysing optical/infrared multi-colour data. The aim is to identify different classes of objects as well as possible undesirable features associated with the construction of colour catalogues. The classification method used is based on the $\chi^2$ -fitting of template spectra to the observed SEDs, as measured through broad-band filters. Its main advantage is the simultaneous use of all colours, properly weighted by the photometric errors. In addition, it provides basic information on the properties of the classified objects (e.g. redshift, effective temperature). These characteristics make the $\chi^2$ -technique ideal for handling large multi-band datasets. The results are compared to the more traditional colour-colour selection and, whenever possible, to model predictions. In order to identify objects with odd colours, either associated with rare populations or to possible problems in the catalogue, outliers are searched for in the multi-dimensional colour space using a nearest-neighbour criterion. Outliers with large $\chi^2$ -values are individually inspected to further investigate their nature. The tools developed are used for a preliminary analysis of the multi-colour point source catalogue constructed from the optical/infrared imaging data obtained for the Chandra Deep Field South (CDF-S). These data are publicly available, representing the first installment of the ongoing EIS Deep Public Survey.

Key words: surveys -- quasars -- stars: white dwarves -- stars: low mass, brown dwarves

Offprint request: E. Hatziminaoglou, ehatzimi@eso.org

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