Spatial Resolution

There are 4 primary configurations (see Table 1) with 6 antennas that can be combined to produce maps with different angular resolution. All four configurations will be available during the winter 2002/2003 observing period.

 

Table: Plateau de Bure configurations with 6 antennas

Configuration	Stations
D	W05	W00	E03	N05	N09	N13
C	W12	E10	E16	N02	N09	N20
B	W12	E04	E23	N07	N17	N29
A	W27	W23	E16	E23	N13	N29

The combinations, named AB, BC, CD are reasonably suited for all declinations (see Table 1 to 3).

• D - the compact configuration with just the D array for maximum sensitivity. This configuration is best suited for detection experiments.

• CD - the next most compact set of configurations which combines the C and D arrays. The beam is slightly asymmetric, but provides more angular resolution compared to the old 5-antenna CD set. Sidelobes at the 10% level are already suppressed to a large extent. This set of configurations is suited for mosaic observations at medium angular resolution.

• BC - a combination of the B and C arrays which gives slightly less resolution compared to the old 5-antenna BC array. It is to be used for relatively strong sources.

• AB - this set of configurations is made up of the A and B arrays and gives a resolution of $\sim 1.3''$ at 115 GHz. Short baselines have been included to facilitate calibration (less decorrelation) and give some sensitivity to extended structure, although this is clearly not the primary goal of the AB configuration.

• A - the most extended configuration with a resolution of $\sim 0.6''$ at 230 GHz. This configuration offers a much higher mapping quality than the old 5-antenna A configuration at the expense of a slightly lower angular resolution. To be used for strong sources.

Mosaicing is usually done with D or CD, but the combination BC+D can also be requested for high resolution mosaics. Lower spatial resolution projects will usually not be considered given the limited field of view of the IRAM interferometer. The antenna beam size is 50" at 100 GHz and the shortest possible spacing is 24 m, to avoid collisions between two antennas. Even taking into account projection effects that shorten the effective baseline, sources larger than about 30" are heavily resolved at 100 GHz.

Non imaging projects, such as detection experiments, size measurements, snapshots, etc., should use a subset of the standard configurations. This subset can either be specified by the observer, or left undefined until final scheduling if any configuration is appropriate (a detection experiment for example).

Table 2-5 gives a summary of beam sizes for natural weighting and various observing frequencies. Observing was supposed to be limited to 6 hours before and after transit and to elevations higher than 20 degrees. Typical $uv$-coverages and resulting beam shapes are shown in Figure 2, Figure 3, and Figure 4.

Beam sizes for configuration D
Dec.	85 GHz		115 GHz		230 GHz		PA
	Maj.	Min.	Maj.	Min.	Maj.	Min.
-20	6.95	6.09	5.14	4.50	2.57	2.25	89.
0	7.69	5.99	5.69	4.43	2.84	2.21	78.
20	7.26	5.15	5.37	3.81	2.68	1.90	87.
40	7.16	4.87	5.29	3.60	2.65	1.80	90.
60	6.99	5.20	5.17	3.84	2.58	1.92	88.
80	6.83	6.04	5.05	4.46	2.52	2.23	89.

Beam sizes for configuration CD
Dec.	85 GHz		115 GHz		230 GHz		PA
	Maj.	Min.	Maj.	Min.	Maj.	Min.
-20	7.25	4.14	5.36	3.06	2.68	1.53	-165.
0	5.48	3.88	4.05	2.87	2.03	1.43	33.
20	4.57	3.71	3.38	2.74	1.69	1.37	57.
40	4.42	3.54	3.27	2.61	1.64	1.31	77.
60	4.39	3.57	3.24	2.64	1.62	1.32	82.
80	4.36	3.96	3.23	2.92	1.61	1.46	86.

Beam sizes for configuration BC
Dec.	85 GHz		115 GHz		230 GHz		PA
	Maj.	Min.	Maj.	Min.	Maj.	Min.
-20	4.96	2.47	3.67	1.83	1.83	0.91	-162.
0	3.66	2.38	2.70	1.76	1.35	0.88	31.
20	3.00	2.31	2.22	1.70	1.11	0.85	46.
40	2.72	2.20	2.01	1.63	1.01	0.81	63.
60	2.61	2.19	1.93	1.62	0.96	0.81	74.
80	2.58	2.38	1.90	1.76	0.95	0.88	80.

Beam sizes for configuration AB
Dec.	85 GHz		115 GHz		230 GHz		PA
	Maj.	Min.	Maj.	Min.	Maj.	Min.
-20	3.82	1.72	2.82	1.27	1.41	0.63	12.
0	2.79	1.71	2.06	1.27	1.03	0.63	-160.
20	2.21	1.74	1.64	1.28	0.82	0.64	29.
40	1.94	1.69	1.43	1.25	0.72	0.63	52.
60	1.86	1.65	1.38	1.22	0.69	0.61	71.
80	1.85	1.73	1.37	1.28	0.68	0.64	81.

Beam sizes for configuration A
Dec.	85 GHz		115 GHz		230 GHz		PA
	Maj.	Min.	Maj.	Min.	Maj.	Min.
-20	3.53	1.36	2.61	1.01	1.30	0.50	9.
0	2.72	1.37	2.01	1.01	1.01	0.51	14.
20	2.06	1.45	1.52	1.07	0.76	0.54	-164.
40	1.68	1.47	1.24	1.08	0.62	0.54	28.
60	1.54	1.43	1.14	1.06	0.57	0.53	60.
80	1.52	1.44	1.12	1.07	0.56	0.53	81.