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D. Scott (UBC), C. Borys, S. C. Chapman (Caltech), M. Donahue (STScI), G. G. Fahlman, M. Halpern, P. Newbury (UBC)
We have discovered what appears to be a giant sub-mm arc, which is coincident with, but much more extended than, a previously known optical arc in the lensing cluster MS0451-03. Without higher resolution sub-mm imaging it is impossible to determine how many separate objects (or images of objects) are contributing to the SCUBA emission. However, the extended ridge of emission lies directly along a portion of the Einstein ring for this cluster, which gives a striking visual demonstration of the reality of gravitationally lensed amplification for sub-mm sources. There can be no doubt that the source of the sub-mm emission lies considerably beyond the z~0.5 of the cluster. Our sub-mm map also demonstrates that not all cosmological observations with SCUBA are at minimal signal-to-noise levels; this single map may in fact contain more total flux than any other "blank field" which has been observed with the JCMT. The best image is derived from a combination of jiggle-map data taken with different chop throws and directions, and is made using direct matrix inversion of the difference data. This approach was necessary because of the strong extended emission in the map, which otherwise was partially chopped out. This is the first time such a technique has been applied to SCUBA data. The lensing amplification through the cluster allows for detailed study of intrinsically fainter sub-mm sources than are possible in the field, and make follow-up observations easier in other wavebands. Existing Chandra X-ray data for this cluster, together with new near-IR imaging have also been compared with the SCUBA image. This may help towards determining the nature of these particular sub-mm sources, as well as understanding the importance of lensing for SCUBA galaxies in general.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.