Extending the variability selection of active galactic nuclei in the W-CDF-S and SERVS/SWIRE region^⋆

¹ Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstraße 25/8, Innsbruck 6020, Austria
e-mail: melina.poulain45@gmail.com, Melina.Poulain@uibk.ac.at
² Department of Physics, University of Napoli “Federico II”, Via Cinthia 9, 80126 Napoli, Italy
³ INFN – Sezione di Napoli, Via Cinthia 9, 80126 Napoli, Italy
⁴ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
⁵ Millennium Institute of Astrophysics (MAS), Nuncio Monseñor Sotero Sanz 100, Providencia, Santiago, Chile
⁶ Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
⁷ Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
⁸ Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
⁹ Space Science Institute, 4750 Walnut Street, Suite 2015, Boulder, CO 80301, USA
¹⁰ KTH Royal Institute of Technology, Brinellvägen 8, 114 28 Stockholm, Sweden
¹¹ Department of Physics, University of Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
¹² Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago, Chile
¹³ Department of Physics and Astronomy, University of the Western Cape, Private Bag X17, 7535 Bellville, Cape Town, South Africa
¹⁴ INAF – Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
¹⁵ School of Physics and Astronomy, Sun Yat-sen University, Zhuhai Campus, Guangzhou 519082, PR China

Received: 13 November 2019
Accepted: 21 December 2019

Abstract

Context. Variability has proven to be a powerful tool to detect active galactic nuclei (AGN) in multi-epoch surveys. The new-generation facilities expected to become operational in the next few years will mark a new era in time-domain astronomy and their wide-field multi-epoch campaigns will favor extensive variability studies.

Aims. We present our analysis of AGN variability in the second half of the VST survey of the Wide Chandra Deep Field South, performed in the r band and covering a 2 sq. deg area. The analysis complements a previous work, in which the first half of the area was investigated. We provide a reliable catalog of variable AGN candidates, which will be critical targets in future variability studies.

Methods. We selected a sample of optically variable sources and made use of infrared data from the Spitzer mission to validate their nature by means of color-based diagnostics.

Results. We obtain a sample of 782 AGN candidates among which 12 are classified as supernovae, 54 as stars, and 232 as AGN. We estimate a contamination ≲20% and a completeness ∼38% with respect to mid-infrared selected samples.