EDP Sciences
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Volume 379, Number 2, November IV 2001
Page(s) 426 - 435
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20011316

A&A 379, 426-435 (2001)
DOI: 10.1051/0004-6361:20011316

Photometric validation of a model independent procedure to extract galaxy clusters

E. Puddu1, S. Andreon1, G. Longo1, 2, V. Strazzullo1, M. Paolillo1, 3 and R. R. Gal4

1  Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
2  Dipartimento di Scienze Fisiche, Università Federico II, Napoli, Italy
3  Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Napoli, Italy
4  Johns Hopkins University, Dept. of Physics and Astronomy, 3701 San Martin Dr., Baltimore, MD 21218, USA

(Received 15 May 2001 / Accepted 20 September 2001 )

By means of CCD photometry in three bands (Gunn g, r, i) we investigate the existence of 12 candidate clusters extracted via a model independent peak finding algorithm (2000) from DPOSS data. The derived color-magnitude diagrams allow us to confirm the physical nature of 9 of the cluster candidates, and to estimate their photometric redshifts. Of the other candidates, one is a fortuitous detection of a true cluster at $z \sim 0.4$, one is a false detection and the last is undecidable on the basis of the available data. The accuracy of the photometric redshifts is tested on an additional sample of 8 clusters with known spectroscopic redshifts. Photometric redshifts turn out to be accurate within $z \sim 0.01$ (interquartile range).

Key words: methods: data analysis -- galaxies: clustering -- galaxies: clusters: photometric redshift

Offprint request: E. Puddu, puddu@na.astro.it

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© ESO 2001