Depletion of background galaxies owing to the cluster lens CL0024+1654: U- and R-band observations |
| |
| Authors: | Ö E Rögnvaldsson T R Greve J Hjorth E H Gudmundsson V S Sigmundsson P Jakobsson A O Jaunsen L L Christensen E van Kampen A N Taylor |
| |
| Institution: | NORDITA, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark;Astronomical Observatory, Univeristy of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark;Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland;Institute of Theoretical Astrophysics, Postboks 1029 Blindern, N-0135 Oslo, Norway;ST-ECF/ESO, Karl‐Schwarzschild‐Strasse 2, D‐85748 Garching, Germany;Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ |
| |
| Abstract: | We have obtained U - and R -band observations of the depletion of background galaxies resulting from the gravitational lensing of the galaxy cluster CL0024+1654 ( z =0.39). The radial depletion curves show a significant depletion in both bands within a radius of 40–70 arcsec from the cluster centre. This is the first time that depletion is detected in the U band. This gives independent evidence for a break in the slope of the U -band luminosity function at faint magnitudes. The radially averaged R -band depletion curve is broader and deeper than in the U band. The differences can be attributed to the wavelength dependence of the slope of the luminosity function and to the different redshift distribution of the objects probed in the two bands. We estimate the Einstein radius, r E, of a singular isothermal sphere lens model using maximum-likelihood analysis. Adopting a slope of the number counts of α =0.2 and using the background density found beyond r =150 arcsec, we find r E=17±3 and 25±3 arcsec in the U and R bands, respectively. When combined with the redshift of the single background galaxy at z =1.675 seen as four giant arcs around 30 arcsec from the cluster centre, these values indicate a median redshift in the range 〈 z S〉≈0.7 to 1.1 for the U AB≥24 mag and R AB≥24 mag populations. |
| |
| Keywords: | gravitational lensing galaxies: clusters: general galaxies: clusters: individual: CL0024+1654 galaxies: statistics ultraviolet: galaxies |
|
|
