A deep optical/near-infrared catalogue of Serpens^*

¹ Research and Scientific Support Department, European Space Agency (ESA-ESTEC), PO Box 299, 2200 AG Noordwijk, The Netherlands e-mail: lspezzi@rssd.esa.int
² European Space Astronomy Center, European Space Agency (ESA-ESAC), PO Box Apdo. de correos 78, 28691 Villanueva de la Cañada, Madrid, Spain
³ California Institute of Technology, Division for Geological and Planetary Sciences, MS 150-21, Pasadena, CA 91125, USA
⁴ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁵ Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany

Received: 23 December 2009
Accepted: 8 February 2010

Abstract

We present a deep optical/near-infrared imaging survey of the Serpens molecular cloud. This survey constitutes the complementary optical data to the Spitzer “Core To Disk” (c2d) Legacy survey in this cloud. The survey was conducted using the wide field camera at the Isaac Newton Telescope. About 0.96 square degrees were imaged in the R and Z filters, covering the entire region where most of the young stellar objects identified by the c2d survey are located. The 26 524 point-like sources were detected in both R and Z bands down to R ≈ 24.5 mag and Z ≈ 23 mag with a signal-to-noise ratio better than 3. The 95% completeness limit of our catalogue corresponds to 0.04  for members of the Serpens star-forming region (age 2 Myr and distance 260 pc) in the absence of extinction. Adopting the typical extinction of the observed area (A_V ≈ 7 mag), we estimate a 95% completeness level down to M ≈ 0.1 . The astrometric accuracy of our catalogue is 0.4 arcsec with respect to the 2MASS catalogue. Our final catalogue contains J2000 celestial coordinates, magnitudes in the R and Z bands calibrated to the SDSS photometric system and, where possible, JHK_S magnitudes from 2MASS for sources in 0.96 square degrees in the direction of Serpens. This data product has already been used within the frame of the c2d Spitzer Legacy Project analysis in Serpens to study the star/disk formation and evolution in this cloud. Here we use it to obtain new indications of the disk-less population in Serpens.