Call for Observing Proposals on the Plateau de Bure Interferometer

Observing proposals are invited for the IRAM Plateau de Bure Interferometer (PdBI), for the period May 15, 1995 to Nov. 15, 1995 . The deadline for applications is Tuesday, February 28th 1995 . The available frequency range will be 82 GHz to 116 GHz.

Details of the PdBI and operations are given in the document ``An Introduction to the IRAM Plateau de Bure Interferometer'' (copies can be obtained from the address below, or from Internet via the World-Wide-Web and NCSA-Mosaic software; use IRAM homepage http://iram.fr/iram.html). Proposers should read this document carefully before submitting any proposal.

Proposals should be sent to IRAM Scientific Secretariat
Interferometer Observing Proposal
300 Rue de la Piscine
F-38406 Saint Martin d'Hères Cedex
FRANCE

IRAM expects to schedule and complete between 20 to 30 projects in this period, with an elapsed time of at least two months between start and end of any given project. Selection will be based on scientific merit, technical feasibility, and adequacy to the instrument.

For this call for proposal, please note the following specificities:

Very long baselines

Phase stability precludes the use of the longest East-West baselines. Standard ``high resolution'' (BC configuration) may be feasible at night time, but cannot be guaranteed. Moreover, work is required this summer to complete the West and North track extension. This may render station N20 unavailable for some time.

230 GHz receivers

Average precipitable water vapor in this period normally precludes 230 GHz observations during the summer period. Accordingly, 230 GHz proposals will not be considered for this period.

However, as an exception, dual-frequency proposals (i.e. proposals in which both the 3mm and 1.3 mm receivers are used) will be considered, under the following restrictions:

• The source should be observable at night during the September to November months.
• 1.3 mm data should not be critical to the success of the project (i.e. the 3mm project should be self-sufficient)
  
• IRAM will not provide any guarantee of results for the 1.3 mm project.

3 Antenna time

As usual in summer time, major maintenance will be carried out, leaving the array with only 3 antennas for one to two months. Projects which can make use of this 3 antenna time, such as detection experiments, are encouraged.

Other relevant information is also given below:

Change of scheduling periods:

IRAM has changed to issuing 2 calls for proposal per year, instead of 3. The two scheduling periods are 15-May to 15-Nov (``Summer Period'') and 15-Nov to 15-May (``Winter Period'').

Configurations:

Two sets of configurations will be available. The "CD" (compact) array is obtained with 3 configurations, and the "BC" (high resolution) array with 4 configurations, with two configurations in common.

We insist that authors specify and carefully justify the requested configuration choice.

Many proposals have been received with insufficient noise estimates. In many cases, a better result can be obtained using lower angular resolution. Combination of all configurations (BCD, 5 configurations in total), is possible, but must be even more justified.

Coordinates and Velocities:

The interferometer now operates in the J2000.0 system. For best positioning accuracy, source coordinates must be in the J2000.0 system; position errors up to may occur otherwise.

Please do not forget to specify LSR velocities for the sources. For pure continuum projects, the ``special'' velocity NULL (no Doppler tracking) can be used.

Correlator:

The correlator has 6 independent units, each being tunable anywhere in the 130-610 MHz band, and providing 4 choices of bandwidth/channel configuration: 160 MHz/64, 80 MHz/128, 40 MHz/256 and 20 MHz/256. For the 40, 80 and 160 MHz bandwidth, the two central channels may be perturbed by the Gibbs phenomenon (depending on continuum strength): it is recommended to avoid centering the most important part of the lines in the middle of the band of the correlator unit.

Receivers:

In the 3 mm band, receivers offer best performances in Lower sideband, with high rejection (10 to 20 dB). Below 100 GHz, expected system temperatures are () 150 K to 200 K for the summer period. DSB tuning is possible also below 100 GHz, but not guaranteed above 100 GHz.

The 1.3 mm receivers are expected to give K, with DSB tuning.

Sun Avoidance:

For safety reasons, the sun avoidance circle has been extended to 45 degrees. Please take this into account for your sources AND for the calibrators.

Mosaics:

The PdBI has mosaicing capabilities, but the pointing accuracy may be a limiting factor at the highest frequencies. Please contact S.Guilloteau in case of doubts.

Data reduction:

Proposers should be aware of constraints for data reduction:

• In general, data will be reduced in Grenoble. Proposers will not come for the observations, but will have to come for the reduction.
• We keep the data reduction schedule very flexible, but wish to avoid the presence of more than 2 groups at the same time in Grenoble. Please contact us in advance.
• IRAM may consider splitting the data reduction in two phases: intermediate calibration and final mapping. Such a splitting is often absolutely necessary for the high resolution images. In such a case, the proposers must be ready to come at IRAM for fast data reduction of the ``compact'' configurations.
• CLIC is still evolving fast to cope with the evolution of the PdBI array. The newer versions are upward compatible with the previous releases, but the reverse is not true. Observers wanting to finish data reduction at their home institute should obtain an updated version of CLIC, which is now available. Since CLIC maintenance is a heavy and tricky task, we insist that observers having a copy of CLIC take special care in maintaining it up-to-date.

Data reduction will be carried out on the dedicated HP workstation.

Local contact:

Depending upon the program complexity, IRAM may require an in-house collaborator instead of the normal local contact.

Technical pre-screening:

All proposals will be reviewed for technical feasibility in parallel to being sent to the members of the program committee. Please help in this task by submitting technically precise proposals. Scientific justification should be kept within 2 pages. Note that your proposal must be complete and exact: velocities, position and frequency setup must be exactly specified.

Non-standard observations:

Please contact S.Guilloteau in case of doubt about non-standard program feasibility.

The documentation for the IRAM Plateau de Bure interferometer includes documents of general interest to potential users:

• An Introduction to the IRAM Plateau de Bure Interferometer.
• IRAM Plateau de Bure Interferometer: Calibration CookBook.
• IRAM Plateau de Bure Interferometer: Mapping CookBook.
• IRAM Plateau de Bure Interferometer: Frequency Setup.
• CLIC: Continuum and Line Interferometer Calibration.

• IRAM Plateau de Bure Interferometer: OBS Users Guide.
• IRAM Plateau de Bure Interferometer: Amplitude Calibration.
• IRAM Plateau de Bure Interferometer: Flux Measurements.
• IRAM Plateau de Bure Interferometer: Pointing Parameters.
• IRAM Plateau de Bure Interferometer: Trouble Shooting Guide.

Finally, we would like to stress again the importance of the quality of the observing proposal. The technical preparation of observing proposals is unfortunately often insufficient. In the past, proposals were received which did not even include exact observing frequencies or even source coordinates, or worse, with coordinates with the wrong epoch !... The IRAM interferometer is a powerful, but complex and unique instrument, and proposal preparation requires special care. Information is available in the documentation, and the IRAM staff can help in case of doubts if contacted well before the deadline. Note that the proposal should not only justify the scientific interest, but also demonstrate how the Plateau de Bure interferometer will bring new information.

Stéphane GUILLOTEAU