Our results are summarized in Table 1. Positions refer to the positions provided by the COSMOS catalog, or for sources below the COSMOS plate limit to detections on our EFOSC images, adopting the astrometry of the COSMOS plates. Position errors are about r.m.s. Magnitudes are values provided by COSMOS, except for , where magnitudes are derived from our EFOSC imaging, calibrated using the COSMOS magnitudes of other sources in the field. Since this procedure ignores the differences between and the Bessel B filter used in EFOSC, for this object is only approximate. Far-IR luminosities have been calculated from where is the luminosity distance and
(see Sanders & Mirabel 1996 and references therein). This procedure somewhat underestimes the total far-IR luminosity because it does not include a K-correction. An accurate K-correction is not possible because of the lack of knowledge of the SED of the sources. However, under the assumption that the SED is similar to that of the prototypical ULIG , we find that the underestimate introduced by Eq. (4) could be up to 50% for the most distant objects.
Notes on individual sample sources:
In addition, we observed one object not in our sample of 6 candidate distant objects, , in order to check possible misidentification, since the only likely counterpart was classified by COSMOS as a fairly bright star with low axial ratio. However, this object is in fact a galaxy with a possible tail or extension towards the east, and showing , , H and  emission lines at . The COSMOS position for this object is R.A. (1950) = , Dec. (B1950) = and its far-IR luminosity is . Accounting for the flux beyond 100 µm, this object is also a ULIG.
© European Southern Observatory (ESO) 1999
Online publication: February 23, 1999