SIMBAD references

We calculate the expected number of multiply imaged galaxies in the Hubble Deep Field (HDF), using photometric redshift information for galaxies with m_I<27 that were detected in all four HDF passbands. A comparison of these expectations with the observed number of strongly lensed galaxies places a lower limit on the current value of Ω_m-Ω_Λ, where Ω_m is the cosmological mass density of the universe and Ω_Λ is the normalized cosmological constant. Based on current estimates of the HDF luminosity function and associated uncertainties in individual parameters, our 95% confidence lower limit on Ω_m-Ω_Λ is between -0.44, if there are no strongly lensed galaxies in the HDF, and -0.73, if there are two strongly lensed galaxies in the HDF. For a flat universe (Ω_m+Ω_Λ=1), Ω_Λ<0.58-0.79 (95% confidence limit). If the only lensed galaxy in the HDF is the one presently viable candidate, then in a flat universe (Ω_m+Ω_Λ=1), Ω_Λ<0.79 (95% confidence limit). These lower limits are compatible with estimates based on high-redshift supernovae and with previous limits based on gravitational lensing.