We are pleased to announce first light in the frequency bands 1291 GHz (Band 2) and GHz (extended Band 3) with the Plateau de Bure interferometer. The two additional RF bands of the new generation receivers (Fig. 1) are now available for astronomical research.
First fringes were observed at 146 GHz with the six-element array on December 15, 2007 towards the high mass star forming region W3(OH) (Fig. 2). By opening Band 2 to astronomical research, the interferometer provides for the first time the opportunity to observe in the GHz frequency window, and this with excellent sensitivity, as apparent from the noise performance of Band 2 (Fig. 3).
Not much later, another milestone was reached. On January 07, 2008, the Plateau de Bure interferometer detected first fringes at 267 GHz on the circumbinary ring in the well-known T Tauri star GG Tau (Fig. 4). The very good sensitivity of Band 3 ( GHz with a median SSB Trec of 70 K at 267 GHz) and the extended frequency coverage result from two major modifications: an improved noise performance of the IF amplifier circuitry and the transition to a new generation of frequency multipliers in the LO system. The enhanced capabilities of the PdBI receivers are particularly gratifying as they are likely to trigger a flood of exciting observations e.g. in the line transitions of HCO and HCN, in the Milky Way and in nearby galaxies.
The analysis of recent test data, and of the few science programs that we have already observed, demonstrate the potential and the new capabilities of the Plateau de Bure interferometer at 2 mm and 1.1 mm, indicating that the performance goals were largely achieved in both frequency bands. The early results of two science demonstration programs are shown in Figure 2 and 4. They illustrate the good performance of the new system. These achievements are the result of years of work of the receiver group, the mechanical construction and workshop group, the SIS group, the computer group, the scientific software group, the science operation group and the telescope operators.
We are now on the way to reach the next two milestones: (1) complete the construction of WideX, a broadband correlator with 4 GHz frequency coverage in each polarization and a channel spacing of 2 MHz and (2) equip the cryostats with Band 4 for operations in the GHz band. Both projects are progressing well, and we are confident to bring them to first light in 2009.
In closing, we would like to invite you to submit projects for the new bands at the March 13, 2008 deadline, and look forward to a year of smooth operations and exciting science results with the new capabilities of the Plateau de Bure array.