The GALEX Ultraviolet Virgo Cluster Survey (GUViCS)

V. Ultraviolet diffuse emission and cirrus properties in the Virgo cluster direction^⋆

¹ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
e-mail: samuel.boissier@lam.fr
² INAF-Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, italy
³ Centro de Astronomia e Astrofísica da Universidade de Lisboa, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
⁴ Instituto de Astrofísica e Ciencias do Espaço, Universidade de Lisboa, OAL, Tapada da Ajuda, 1349-018 Lisboa, Portugal
⁵ University of California Observatories/Lick Observatory, University of California Santa Cruz, Department of Astronomy & Astrophysics, 1156 High Street, Santa Cruz, CA 95064, USA
⁶ Department of Astronomy, University of Maryland, Stadium Drive, College Park, MD 20742-2421, USA
⁷ Centre for Astrophysics & Supercomputing, Swinburne University of Technology, Mail H29 – PO Box 218, Hawthorn VIC 3122, Australia
⁸ Laboratoire AIM, Service d’astrophysique, CEA-Saclay, Orme des merisiers, Bâtiment 709, 91191 Gif-sur-Yvette Cedex, France
⁹ School of Physics and Astronomy, Cardiff University, The Parade, Cardiff, CF24 3AA, UK

Received: 13 March 2015
Accepted: 21 April 2015

Abstract

Context. The Virgo direction has been observed at many wavelengths in recent years, in particular in the ultraviolet with GALEX. The far ultraviolet (FUV) diffuse light detected by GALEX offers interesting information on the large scale distribution of Galactic dust, owing to the GALEX FUV band sensitivity and resolution.

Aims. We aim to characterise the ultraviolet large scale distribution of diffuse emission in the Virgo direction. A map of this emission may become useful for various studies by identifying regions where dust affects observations by either scattering light or absorbing radiation.

Methods. We constructed mosaics of the FUV and near ultraviolet (NUV) diffuse emission over a large sky region (RA 12 to 13 h, Dec 0 to 20 deg) surrounding the Virgo cluster, using all the GALEX available data in the area. We tested for the first time the utilisation of the FUV diffuse light as a Galactic extinction E(B − V) tracer.

Results. The FUV diffuse light scattered on cirrus reveals details about their geometry. Despite large dispersion, the FUV diffuse light correlates roughly with other Galactic dust tracers (coming from IRAS, Herschel, Planck), offering an opportunity to use the FUV emission to locate them in future studies with a better resolution (about 5 arcsec native resolution, 20 arcsec pixels maps presented in this paper) than for several usual tracers. Estimating the Galactic dust extinction on the basis of this emission allows us to find a smaller dispersion in the NUV − i colour of background galaxies at a given E(B − V) than with other tracers. The diffuse light mosaics obtained in this work are made publicly available.