R. S. Pawase, C. Faure, F. Courbin, R. Kokotanekova, G. Meylan
We present the results of a visual search for galaxy-scale gravitational lenses in ~7 square degrees of Hubble Space Telescope (HST) images. The dataset comprises the whole imaging data ever taken with the Advanced Camera for Surveys (ACS) in the filter F814W (I-band) up to August 31st, 2011, i.e. 6.03 square degrees excluding the field of the Cosmic Evolution Survey (COSMOS). In addition, we have searched for lenses in the whole Wide Field Camera 3 (WFC3) near-IR imaging dataset in all filters 1.01 square degree up to the same date. Our primary goal is to provide a sample of lenses with a broad range of different morphologies and lens-source brightness contrast in order to design and train future automated lens finders in view of all-sky surveys. Our criteria to select lenses are purely morphological as we do not use any color or redshift information. The final candidate selection is very conservative hence leading to a nearly pure but incomplete sample. We find 49 new lens candidates: 40 in the ACS images and 9 in the WFC3 images. Out of these, 16 candidates are secure lenses owe to their highly recognizable morphology, 21 more are very good candidates, and 12 more have morphologies compatible with gravitational lensing. The imaging dataset is heterogeneous in depth and spans a broad range of galactic latitudes. It is therefore insensitive to cosmic variance and allows to estimate the number of galaxy-scale strong lenses on the sky for a putative survey depth. Because of the incompleteness of the sample, the estimated lensing rates should be taken as lower limits. Using these, we anticipate that a 15000 square degrees space survey such as Euclid will find at least 60000 galaxy-scale strong lenses down to a limiting AB magnitude of I=24.5 (10-sigma) or I=25.8 (3-sigma).
View original:
http://arxiv.org/abs/1206.3412
No comments:
Post a Comment