Deep U-B-V imaging of the Lockman Hole with the LBT^*

Observations and number counts

¹ Max Planck Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany e-mail: erovilos@mpe.mpg.de
² Institute of Physics, Eötvös University, Pázmány P. s. 1/A, 1117 Budapest, Hungary
³ Max Planck Institut für Plasmaphysik, Boltzmannstraße 2, 85748, Garching, Germany
⁴ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
⁵ California Institute of Technology, MC 205-24, 1200 East California Boulevard, Pasadena, CA 91125, USA

Received: 3 June 2009
Accepted: 25 August 2009

Abstract

We used the large binocular camera (LBC) mounted on the large binocular telescope (LBT) to observe the Lockman Hole in the U, B, and V bands. Our observations cover an area of 925 arcmin². We reached depths of 26.7, 26.3, and 26.3 mag(AB) in the three bands, respectively, in terms of 50% source detection efficiency, making this survey the deepest U-band survey and one of the deepest B and V band surveys with respect to its covered area. We extracted a large number of sources (~89 000), detected in all three bands and examined their surface density, comparing it with models of galaxy evolution. We find good agreement with previous claims of a steep faint-end slope of the luminosity functions, caused by late-type and irregular galaxies at . A population of dwarf star-forming galaxies at is needed to explain the U-band number counts. We also find evidence of strong supernova feedback at high redshift. This survey is complementary to the r, i, and z Lockman Hole survey conducted with the Subaru telescope and provides the essential wavelength coverage to derive photometric redshifts and select different types of sources from the Lockman Hole for further study.