Call for Observing Proposals on the Plateau de Bure Interferometer

Conditions for the next winter session

The construction of the sixth antenna is progressing well, but the antenna should become operational by the end of the year, at the earliest. Investigators are therefore asked to submit proposals on the availability of five antennas only. Projects will be properly adjusted in observing time and uv-coverage as soon as the sixth antenna should become available.

As last winter, we will still rely on ground transport and transport by helicopter. This will limit the number of people on the site and so our ability to carry out configuration changes under typical winter conditions. We therefore ask investigators to submit proposals for the D, C2 and B1 configurations only. The D and C2 configurations have already been offered last winter. These configurations provide already a large number of possibilities: deep integrations (D), low (CD) and medium to high (BC) resolution observations in the snapshot, mapping or mosaicing modes. The BC set of configurations, for instance, provides an angular resolution better than 1 $\hbox{$^{\prime\prime}$ }$ at 230 GHz and 30$^\circ$ declination. The scheduling priority is expected to be on the D configuration until December and towards end of the winter session, more extended configurations (C2 and B1) are likely not to be scheduled before.

Applications should also take into account the capabilities of the new six antenna correlator. Please note that the instrumental bandwidth will be limited by the receivers, i.e. the extended bandwidth of the correlator will not yet be fully available on the sky.

Call for Proposals

Observing proposals are invited for the Plateau de Bure Interferometer for the period Nov 15, 2001 to May 15, 2002. The deadline for applications is September 5th, 2001 16:00h (MET).

Under normal operating conditions, IRAM schedules and completes between 30 and 50 projects during the winter period, with an elapsed time of at least two months between start and end of any given project. Selection is based on scientific merit, technical feasibility, and adequacy to the instrument.

Details of the PdBI and the observing procedures are given in the document ``The Plateau de Bure Interferometer (PdBI)''. A copy can be obtained from the address below or from the World-Wide-Web at http://iram.fr/PDBI/bure.html). Proposers should read this document carefully before submitting any proposal.

We strongly encourage the submission via the electronic submission facility available at http://iram.fr/submission/submission.html. Note that applications sent by e-mail will not be accepted. Applications sent by fax or postal mail should be addressed to:

IRAM Scientific Secretariat
Interferometer Observing Proposal
300 Rue de la Piscine
F-38406 Saint Martin d'Hères Cédex
FRANCE

Proposal templates proposal.tex as well as the Latex style file proposal.sty can be retrieved by anonymous ftp from iram.fr (in directory dist/proposal); or from the Internet via the World-Wide-Web at http://iram.fr/proposal/proposal.html. In case of problems, contact the scientific secretary, Mrs Cathy Berjaud (berjaud@iram.fr).

Do not use characters smaller than 11pt, which could make your proposal illegible when duplicated or faxed. For the same reasons, also avoid sending figures with grey scale maps by fax. In case your proposal reaches us in time, but is incomplete or unreadable when copied, we will try our best to contact you. The Principal Investigator will receive by return mail an acknowledgement of receipt and the proposal number.

The scientific aims of the proposed programme should be explained in 2 pages of text maximum, plus up to two pages of figures, tables, and references. Proposals should be self-explanatory, clearly state their aims, and explain the need of the Plateau de Bure interferometer.

In all cases, indicate on the first page whether your proposal is (or is not) the resubmission of a proposal or the continuation of a previously accepted proposal. In the case of a resubmission, state very briefly in the introduction why the proposal is being resubmitted (e.g. improved scientific justification, observational restrictions).

For this call for proposals, please note the following guidelines.

Proposal category

Proposals should be submitted for one of the five categories:

1.3mm:

Proposals that ask for 1.3mm data only. 3mm receivers will be used for pointing and calibration purposes, but cannot provide any imaging.

3mm:

Proposals that ask for 3mm data only. 1.3 mm receivers can still be used to provide either phase stability information or purely qualitative information such as the mere existence of fringes.

dual freq.:

Proposals that ask for dual-frequency observations (i.e. simultaneous observations at 3mm and 1.3mm).

time filler:

Proposals that have to be considered as background projects to fill in periods where the atmospheric conditions do not allow mapping, or eventually, to fill in gaps in the scheduling, or even periods when only a subset of the standard 5-antenna configurations will be available. These proposals will be carried out on a ``best effort'' basis only.

special:

Exploratory proposals: proposals whose scientific interest justifies the attempt to use the PdB array beyond its guaranteed capabilities. This category includes for example non-standard frequencies for which the tuning cannot be guaranteed, and more generally all non-standard observations. These proposals will be carried out on a ``best effort'' basis only.

The proposal category will have to be specified on the proposal cover sheet and should be carefully considered by proposers.

Configurations

The configurations for the winter period will be:

5 Antenna configurations
Name	Stations
D	W05 W00 E03 N05 N09
C2	W12 W09 E10 N05 N15
B1	W12 E18 E23 N13 N20

Projects will be properly adjusted in observing time and uv-coverage as soon as the sixth antenna becomes available. Investigators are asked to indicate possible tradeoffs should the requested configuration not be available.

The following configuration sets are available:

Set	Configs	Main purpose
D	D	Detection, ``Low'' resolution mapping at 1.3 mm
CD	D, C2	3.5 $\hbox{$^{\prime\prime}$ }$ resolution at 3mm, 1.8 $\hbox{$^{\prime\prime}$ }$ resolution at 1.3 mm
BC	B1, C2	2 $\hbox{$^{\prime\prime}$ }$ resolution at 3 mm

Enter ANY in the proposal form if your project doesn't need a particular configuration.

Receivers

All antennas are equipped with fully operational dual frequency receivers. The available frequency range will be 82 GHz to 116 GHz for the 3mm band, and 205 to 245 GHz for the 1.3 mm band. The 3mm and 1.3mm receivers are aligned to within $\approx 2\hbox{$^{\prime\prime}$ }$.

Below 105 GHz, receivers offer best performances in LSB tuning with high rejection (20 dB): expected system temperatures are (in $T_{\rm R}^{*}$ scale) 100 to 150 K for the winter time. Above 110 GHz, best performances are obtained with USB tuning, low rejection (4 to 6 dB): expected system temperatures are 250 K at 115 GHz.

The 1.3 mm receivers give DSB tuning with typical T $_{\rm REC}$ below 50 K. Expected SSB system temperature are 250 to 350 K. The guaranteed tuning range is 205-245 GHz, but it may be possible to reach lower frequencies for specific cases. Higher frequencies are not feasible because of limitations in the triplers.

Atmospheric phase compensation

Software is available to provide real-time atmospheric phase compensation on spectral and continuum data, as well as a-posteriori processing for continuum data. Experience shows that a final phase noise below 30$^\circ$ at 230 GHz may be obtained under good circumstances.

Signal to Noise

The rms noise can be computed from

$$\sigma = \frac{\mbox{$J_{\rm pK}$ }\mbox{$T_{\rm SYS}$ }}{\et... ...{$N_{\rm a}$ }(\mbox{$N_{\rm a}$ }-1) \mbox{$N_{\rm c}$ }T B}}$$ (1)

where

•   $\mbox{$T_{\rm SYS}$ }$ is the system temperature in T_r^* scale (150 K below 110 GHz, 300 K at 115 GHz, 500 K at 230 GHz)
•   $\mbox{$J_{\rm pK}$ }$ is the conversion factor from Kelvin to Jansky (22 at 3mm, 35 at 1.3mm)
•  $\eta$ is an efficiency factor due to atmospheric phase noise (0.9 at 3 mm, 0.8 at 1.3 mm)
•   $\mbox{$N_{\rm a}$ }$ is the number of antennas (5), and $\mbox{$N_{\rm c}$ }$ is the basic number of configurations (1 for D, 2 for CD, 2 for BC)
•  T is the integration time per configuration in seconds (3 to 8 hours, depending on source declination)
•  B is the channel bandwidth in Hz (500 MHz for continuum, 40 kHz to 2.5 MHz for spectral line, according to spectral correlator setup)

Investigators have to specify the one sigma noise level which is necessary to achieve each individual goal of a proposal, and in particular for projects aiming at deep integrations.

Coordinates and Velocities

The interferometer operates in the J2000.0 system. For best positioning accuracy, source coordinates must be in the J2000.0 system; position errors up to $0.3\hbox{$^{\prime\prime}$ }$ 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.

Coordinates and velocities in the proposal MUST BE CORRECT: A coordinate error is a potential cause for proposal rejection.

Correlator

The new correlator has 8 independent units, each being tunable anywhere in the 110-680 MHz band, and providing 7 different modes of configuration (characterized in the following by pairs of numbers giving the total bandwidth/number of channels). In the first 3 modes: 320MHz/128, 160MHz/256, 80MHz/512 the two central channels may be perturbed by the Gibbs phenomenon (depending on continuum strength). When using these modes, it is recommended to avoid centering the most important part of the lines in the middle of the band of the correlator unit. In the remaining modes: 160MHz/128, 80MHz/256, 40MHz/512 and 20MHz/512 the two central channels are not affected by the Gibbs phenomenon and, therefore, these modes should be preferred for spectroscopic studies.

The 8 units can be independently placed either on the IF1 (3mm receiver) or on the IF2 (1.3mm receiver).

Sun Avoidance

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

Mosaics

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

Data reduction

Proposers should be aware of constraints for data reduction:

• In general, data should 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.
• In certain cases we give the possibility to eavesdrop on the uv-tables obtained on a project shortly after the observations. Please contact us if you are interested in this option.
• IRAM may consider splitting the data reduction in two phases: intermediate calibration and final mapping. Such a splitting is often 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 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. Because differences between CLIC versions may potentially result in imaging errors if new data is reduced with an old package, we insist that observers using a copy of CLIC take special care in maintaining it up-to-date.

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

Local contact

A local contact will be assigned to every A or B - rated proposal which does not involve an in-house collaborator. Depending upon the programme 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 programme committee. Please help in this task by submitting technically precise proposals. Note that your proposal must be complete and exact: velocities, position and frequency setup must be exactly specified.

Non-standard observations

Please contact R.Neri or R.Lucas in case of doubt about the feasibility of a non-standard program.

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.

More specialized documents are also available; they are intended for observers on the site (IRAM on-duty astronomers, operators, or observers with non-standard programs):

• 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, revealing coordinates with the wrong epoch !... The IRAM interferometer is a powerful, but complex instrument, and proposal preparation requires special care. Information is available in the documentation and at http://iram.fr/PDBI/bure.html. 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.

Roberto NERI