Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA, and made possible by the generous financial support of the W. M. Keck Foundation.

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Tables 5, 6 and Fig. 7 are only available in electronic form at http://www.aanda.org

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...1,2,

S.B. was supported by the Ing. Aldo Gini Foundation

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... MAMBO

Distant ULIRGs are commonly referred to as submillimeter galaxies, or SMGs; here we reserve that term explicitly for systems selected in submm or mm surveys, because distant ULIRGs selected at other wavelengths may not necessarily be (sub)mm-luminous.

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... P3L

P3L sources have IRAC 3.6, 4.5, 5.8 $\mu$ m detection, but only an upper limit at 8.0 $\mu$ m.

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... IRAF

The package IRAF is distributed by the National Optical Astronomy Observatory which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.

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... webpage

http://www2.keck.hawaii.edu/inst/lris/

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... objects

Note that a couple of targets were observed twice, in distinct masks, therefore the effective number of targets is 233 in 235 slitlets.

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... respectively

These numbers don't include serendipitous sources.

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... distribution

Here $\Delta$ is the difference between the photometric and spectroscopic redshift estimates.

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