White dwarfs in the Capodimonte deep field^*

¹ INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy e-mail: [silvotti;jmae;agrado]@na.astro.it
² Institut de Ciències de l'Espai, (CSIC-IEEC), Facultat de Ciències, Campus UAB, 08193 Bellaterra, Spain e-mail: catalan@ieec.uab.es
³ Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: michele.cignoni@unibo.it
⁴ Dipartimento di Scienze Fisiche, Università Federico II, via Cintia, 80126 Napoli, Italy e-mail: capaccioli@na.infn.it
⁵ INAF-VSTceN, via Moiariello 16, 80131 Napoli, Italy
⁶ National Radio Astronomy Observatory (NRAO), PO Box O, 1003 Lopezville Road, Socorro, NM 87801-0387, USA e-mail: mpannell@nrao.edu

Received: 23 November 2007
Accepted: 21 November 2008

Abstract

Aims. In this article we describe the search for white dwarfs (WDs) in the multi-band photometric data of the Capodimonte deep field survey.

Methods. The WD candidates were selected through the V-R_C vs. color–color diagram. For two bright objects, the WD nature has been confirmed spectroscopically, and the atmospheric parameters (T_eff and log g) have been determined. We have computed synthetic stellar population models for the observed field and the expected number of white dwarfs agrees with the observations. The possible contamination by turn-off and horizontal branch halo stars has been estimated. The quasar (QSO) contamination has been determined by comparing the number of WD candidates in different color bins with state-of-the-art models and previous observations.

Results. The WD space density is measured at different distances from the Sun. The total contamination (non-degenerate stars + QSOs) in our sample is estimated to be around 30%. This work should be considered a small experiment in view of more ambitious projects to be performed in the coming years in larger survey contexts.