Galaxy Counts at 450 Μm and 850 Μm

Surveys of the distant Universe have been made using the SCUBA submillimeter(submm)-wave camera at the JCMT. 450and 850μm data is taken simultaneously by SCUBA in the same 5-arcmin2 field. Deep 850-μm counts of high-redshift dusty galaxies have been published; however, at 450 μm both the atmospheric transmission and antenna efficiency are lower, and the atmospheric noise is higher, and so only upper limits to the 450-μm counts have been reported so far. Here we apply the methods used by Blain et al. (1999) to derive deep 850-μm counts from SCUBA images of lensing clusters to the 450-μm images that were obtained in parallel, in which four sources were detected. We present the first 450-μm galaxy count. This analysis has only just become possible because the volume of data and the difficulty of calibration are both greater for the 450-μm array. In light of recent work, in which the identification of two of the galaxies in our sample was clarified, we also update our deep 850-μm counts.