A Winter Night's Dream: First Light at 256 GHz with the Plateau de Bure Interferometer.

The New Generation Receivers (NGRx) project is one of the most challenging and ambitious projects IRAM has been developing in the last years. As the result of a combined and concerted team effort, the installation of the NGRx was done on schedule and was followed by a successful test and science commissioning phase. The delivery of the first two receiver bands (86 - 116 GHz and 202 - 257 GHz) to the astronomical community was effective as of January 18th, 2007.

A highlight of the NGRx is the first-light at 256 GHz, which was obtained during the night of January 28th, 2007. This is the highest frequency ever observed with the Plateau de Bure Interferometer. At 22:45 UT Andre Rambaud and Patrick Chaudet, operators at the Plateau de Bure observatory, tuned the 1mm bands of the NGRx to observe the fine structure line of [CII] in the host galaxy of the highest redshift QSO J1148+5251 (z=6.42). After only 3.5 hours on-source, a clear detection of the [CII] emission line was achieved together with the underlying continuum (Fig. 1). The PdBI result is in perfect agreement with the spectrum of the 30-meter telescope which was obtained after 12.4 hours on-source integration time (Maiolino et al. 2005).

**Figure 1:** Spectrum of the [CII] 157.74 microns emission line in the quasar J1148+5251 observed at a redshift of 6.42. The data are shown with a spectral resolution of 10 km/s and were obtained in only 3.5 hours with the New Generation Receivers on the Plateau de Bure interferometer in the D configuration. The observed frequency (256.17 GHz) is the highest frequency ever observed at the PdBI. The solid line shows the Gaussian fit to both the underlying continuum and the line profile.
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This exciting result illustrates the excellent performance and sensitivity of the NGRx which we are pleased to share with you. Today the NGRx band at 3mm and 1mm are running without any problem to perform regular astronomical observations, weather permitting. The next plans are to install the 2mm band which will become available for the winter period of 2007/2008 and to deliver the 0.8mm band for the winter 2008/2009 scheduling period. This will conclude the NGRx project and provide the PdBI with a unique suite of receivers operating from 3 to 0.8 mm with high sensitivities.