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arXiv · 1108.4681

The serendipitous observation of a gravitationally lensed galaxy at z = 0.9057 from the Blanco Cosmology Survey: The Elliot Arc

E. J. Buckley-Geer·H. Lin·E. R. Drabek·S. S. Allam·D. L. Tucker·R. Armstrong·W. A. Barkhouse·E. Bertin·M. Brodwin·S. Desai·J. A. Frieman·S. M. Hansen·F. W. High·J. J. Mohr·Y. -T. Lin·C. -C. Ngeow·A. Rest·R. C. Smith·J. Song·A. Zenteno
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Abstract

We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z = 0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z=0.3838. The lens (BCS J2352-5452) was discovered while examining i- and z-band images being acquired in October 2006 during a BCS observing run. Follow-up spectroscopic observations with the GMOS instrument on the Gemini South 8m telescope confirmed the lensing nature of this system. Using weak plus strong lensing, velocity dispersion, cluster richness N_200, and fitting to an NFW cluster mass density profile, we have made three independent estimates of the mass M_200 which are all very consistent with each other. The combination of the results from the three methods gives M_200 = (5.1 +- 1.3) x 10^14 M_Sun, which is fully consistent with the individual measurements. The final NFW concentration c_200 from the combined fit is c_200 = 5.4(+1.4 -1.1). We have compared our measurements of M_200 and c_200 with predictions for (a) clusters from Lambda_CDM simulations, (b) lensing selected clusters from simulations, and (c) a real sample of cluster lenses. We find that we are most compatible with the predictions for Lambda_CDM simulations for lensing clusters, and we see no evidence based on this one system for an increased concentration compared to Lambda_CDM. Finally, using the flux measured from the [OII]3727 line we have determined the star formation rate (SFR) of the source galaxy and find it to be rather modest given the assumed lens magnification.

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E. J. Buckley-Geer, H. Lin, E. R. Drabek, S. S. Allam, D. L. Tucker, R. Armstrong, W. A. Barkhouse, E. Bertin, M. Brodwin, S. Desai, J. A. Frieman, S. M. Hansen, F. W. High, J. J. Mohr, Y. -T. Lin, C. -C. Ngeow, A. Rest, R. C. Smith, J. Song, A. Zenteno. 2011-09-08. The serendipitous observation of a gravitationally lensed galaxy at z = 0.9057 from the Blanco Cosmology Survey: The Elliot Arc. https://doi.org/10.1088/0004-637x%2F742%2F1%2F48

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