Call for Observing Proposals on the Plateau de Bure Interferometer

Conditions for the next summer period

As every year, we plan to carry out extensive technical work during the summer period. Besides the usual maintenance of the antennas we plan this year to complete the northern track extension and start testing of N46, the new station at the end of the northern track. We hope to make it ready in time for the next winter period. At the same time, and if possible, we plan to proceed also with work on extending the eastern track, which, according to plans, should become available for the winter 2006/2007 scheduling period.

In parallel to these activities, we plan to carry out regular scientific observations during the whole period with the five element array. Taking these considerations into account, we are confident to be able to schedule about 20 to 30 projects.

We plan to start the maintenance before the end of May and to schedule the C and D configurations between June and October. For observations at high-angular resolution, we tentatively plan a move to the more extended B configuration and the switch back to the six element array for the end of October, i.e. before the end of the scheduling period.

We strongly encourage observers to submit proposals that can be executed during summer operating conditions. To keep the procedure as simple as possible, we ask to focus on:

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observations requesting the use of the 3mm receivers

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circumpolar sources or sources transiting at night between June and September,

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observations that qualify for the C and D configurations with 5 antennas.

For this call for proposals, note also the following aspects.

Proposal category

Proposals should be submitted for one of the five categories:

3MM:

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

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.

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, non-standard configurations 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

Standard configurations for the summer period are:

5 antenna configurations
Name	Stations
D	W05 W00 E03 N05 N09
C	W12 W09 E10 N05 N15
B	W12 E18 E23 N13 N20

Part of the projects will be scheduled at the end of the summer period when the six-element array is expected to be back in operation. Projects that will be observed with a subset of the five-element array, will be adjusted in uv-coverage and observing time.

The following configuration sets are available:

Set	Main purpose
D	``Low'' resolution at 1.3mm
CD	3.5$''$ resolution at 3mm
BC	2$''$ resolution at 3mm

Finally, enter ANY in the proposal form if your project doesn't need any particular configuration. The scheduling of the B configuration depends on weather conditions and pressure on the C and D configurations, but will not be scheduled before the end of October.

Receivers

All antennas are equipped with fully operational dual frequency receivers. The available frequency range is 82GHz to 116GHz for the 3mm band, and 210 to 245GHz for the 1.3mm band. The 3mm and 1.3mm receivers are aligned to within about $2''$.

Below 105GHz, receivers offer best performances in LSB tuning with high rejection (20dB): expected system temperatures are 150 to 200K for the summer time. Above 105GHz, best performances are obtained with USB tuning, low rejection (4 to 6dB): expected system temperatures are 300 to 450K at 115GHz. DSB tuning is possible over the whole frequency range, but the system temperature may degrade significantly. The 1.3mm receivers give DSB tuning with typical T$_{\rm REC}$ below 50K. Expected SSB system temperature are 500K.

The guaranteed tuning ranges are 82-116GHz and 205-245GHz. For details about observing at frequencies beyond the guaranteed tuning range of the 3mm and 1.3mm receivers, please get in touch with the Science Operations Group (sog@iram.fr).

Signal to Noise

The rms noise can be computed from

$$\sigma = \frac{J_{\rm pK} T_{\rm sys}} {\eta \sqrt{N_{\rm a} (N_{\rm a}-1) N_{\rm c} T_{\rm ON} B}}$$ (1)

where

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$T_{\rm sys}$ is the system temperature in $T_A^{*}$ scale (150K below 110GHz, 300K at 115GHz, 500K at 230GHz for sources at $\ge 20^\circ$),

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$J_{\rm pK}$ is the conversion factor from Kelvin to Jansky (22 at 3mm, 35 at 1.3mm),

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$\eta$ is an efficiency factor due to atmospheric phase noise (0.9 at 3mm, 0.8 at 1.3mm),

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$N_{\rm a}$ is the number of antennas (5), and $N_{\rm c}$ is the basic number of configurations (1 for D, 2 for CD, 2 for BC, and so on)

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$T_{\rm ON}$ is the integration time per configuration in seconds (2 to 8 hours, depending on source declination). Because of calibrations and antenna slew time, the effective on-source time is about 60-70% of the total observing time,

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$B$ is the channel bandwidth in Hz (580 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 particularly 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 $0.3''$ 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 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 couples of total bandwidth/number of channels). In the first 3 modes (LSB+USB): 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 (LSB or USB): 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). For more details, please refer to the Web page at http://www.iram.fr/TA/backend/cor6A/

Sun Avoidance

For safety reasons, a sun avoidance circle has been set 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 the Science Operations Group (sog@iram.fr) in case of doubts.

Data reduction

Proposers should be aware of constraints for data reduction:

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In general, data should be reduced in Grenoble. Proposers will not come for the observations, but are advised to come for the reduction. Remote data reduction is possible, especially for experienced users of the Plateau de Bure Interferometer. Please contact your local contact if you're interested in this possibility.

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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.

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In certain cases, proposers may have a look at the uv-tables as the observations progress. If necessary, and upon request, more information can be provided. Please contact the Science Operations Group (sog@iram.fr) if you are interested in this.

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CLIC evolves to cope with upgrades of the PdBI array. The newer versions are downward compatible with the previous releases. Observers who wish to finish data reduction at their home institute should obtain the most recent version of CLIC. Because differences between CLIC versions may potentially result in imaging errors if new data are reduced with an old package, we advise observers having a copy of CLIC to take special care in maintaining it up-to-date.

Local Contact

A local contact will be assigned to every A or B rated proposal which does not involve an in-house collaborator. He/she will assist you in the preparation of the observing procedures and provide help to reduce the data. Assistance is also provided before a deadline to help newcomers in the preparation of a proposal. 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: the source position and velocity, as well as the requested frequency setup must be correctly given.

Non-standard observations

If you plan to execute a non-standard program please contact the Science Operations Group (sog@iram.fr) to discuss the feasibility.

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

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An Introduction to the IRAM Plateau de Bure Interferometer.

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IRAM Plateau de Bure Interferometer:
Calibration CookBook.

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IRAM Plateau de Bure Interferometer:
Mapping CookBook.

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IRAM Plateau de Bure Interferometer:
Frequency Setup.

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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):

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IRAM Plateau de Bure Interferometer:
OBS Users Guide.

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IRAM Plateau de Bure Interferometer:
Amplitude Calibration.

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IRAM Plateau de Bure Interferometer:
Flux Measurements.

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IRAM Plateau de Bure Interferometer:
Pointing Parameters.

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IRAM Plateau de Bure Interferometer:
Trouble Shooting Guide.

Roberto NERI