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Spatial Resolution

Four primary 7 antenna configurations (see Table[*]) are available that can be combined to produce maps with different angular resolution. All four configurations are usually scheduled during the course of a year. During the summer period (May until September) each antenna undergoes a thorough maintenance and the interferometer is operated in a 6 antenna D configuration, equal to the 7D configuration given in Table [*] but without station E10).


Table: NOEMA 7 antenna configurations
Configuration Stations
7A W27 W10 E68 E24 E12 N46 N29
7B W23 W05 E24 E18 E04 N46 N20
7C W12 W09 E18 E12 E04 N17 N11
7D W08 W05 E10 E04 N11 N07 N02

The four configurations can be used in different combinations to achieve complementary sampling of the uv-plane, and to improve on angular resolution and sensitivity. The combinations AB, BC, CD are reasonably suited for all declinations above 0$^\circ$(see Tables[*] to [*]). For lower source declinations, the beam becomes increasingly elliptical. Sources lower than -25$^\circ$declination cannot reasonably be observed from Plateau de Bure. Mosaicing is usually done with D or CD, but the combination BCD can also be requested for high resolution mosaics.

The antenna half-power beam size is 50 $^{\prime\prime}$ at 100 GHz and the shortest possible antenna 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 15 $^{\prime\prime}$ are already heavily resolved at 100 GHz. In these cases, additional short-spacing observations should be acquired by observing a raster- or OTF- (On-The-Fly) map using the IRAM 30 m telescope1. The short-spacing information can then easily be added to the uv-tables obtained from the interferometer by means of the GILDAS MAPPING software.

Tables[*]-[*] give a summary of possible beam sizes at various observing frequencies in different configurations using natural weighting. The numbers were obtained assuming observations of the target source from 6 hours before to 6 hours after transit down to elevations above 20 degrees. Typical uv-coverages and resulting beam shapes for the seven-element array are shown in Figs.[*] (D and CD), [*] (BCD and BC), and [*] (A and AB).


Table: Beam sizes for configuration D
Dec. 100 GHz 150 GHz 230 GHz 300 GHz 345 GHz PA
  Maj. Min. Maj. Min. Maj. Min. Maj. Min. Maj. Min. $^\circ$
80 4.54 3.78 3.03 2.52 1.97 1.64 1.51 1.26 1.31 1.09 23
60 4.35 3.61 2.90 2.41 1.89 1.57 1.45 1.20 1.28 1.10 38
40 4.51 3.58 3.00 2.38 1.95 1.60 1.50 1.19 1.30 1.06 36
20 5.07 3.63 3.38 2.42 2.20 1.57 1.69 1.21 1.47 1.05 26
0 6.42 3.69 4.28 2.46 2.79 1.60 2.14 1.23 1.86 1.07 -162
-20 9.80 3.36 6.53 2.24 4.47 1.47 3.26 1.12 2.98 0.98 -173


Table: Beam sizes for configuration CD
Dec. 100 GHz 150 GHz 230 GHz 300 GHz 345 GHz PA
  Maj. Min. Maj. Min. Maj. Min. Maj. Min. Maj. Min. $^\circ$
80 3.44 2.72 2.29 1.81 1.49 1.18 1.14 0.90 0.99 0.78 23
60 3.29 2.59 2.19 1.72 1.43 1.12 1.09 0.86 0.95 0.75 34
40 3.45 2.55 2.30 1.70 1.49 1.10 1.15 0.85 0.99 0.73 32
20 3.96 2.56 2.64 1.70 1.72 1.11 1.32 0.85 1.14 0.74 25
0 5.09 2.60 3.39 1.73 2.21 1.13 1.69 0.86 1.47 0.75 -161
-20 7.52 2.40 5.01 1.60 3.27 1.04 2.50 0.80 2.18 0.69 -172


Table: Beam sizes for configuration C
Dec. 100 GHz 150 GHz 230 GHz 300 GHz 345 GHz PA
  Maj. Min. Maj. Min. Maj. Min. Maj. Min. Maj. Min. $^\circ$
80 2.61 2.04 1.74 1.36 1.13 0.89 0.87 0.68 0.75 0.59 25
60 2.59 1.96 1.72 1.30 1.12 0.85 0.86 0.65 0.75 0.56 32
40 2.72 1.93 1.81 1.28 1.18 0.83 0.90 0.64 0.78 0.55 32
20 3.15 1.95 2.10 1.30 1.37 0.85 1.05 0.65 0.91 0.56 25
0 4.07 1.98 2.69 1.35 1.75 0.88 1.34 0.67 1.18 0.57 19
-20 6.13 1.88 4.09 1.25 2.66 0.81 2.04 0.62 1.77 0.54 8


Table: Beam sizes for configuration BC
Dec. 100 GHz 150 GHz 230 GHz 300 GHz 345 GHz PA
  Maj. Min. Maj. Min. Maj. Min. Maj. Min. Maj. Min. $^\circ$
80 1.91 1.56 1.27 1.04 0.83 0.67 0.63 0.52 0.55 0.45 35
60 1.91 1.48 1.27 0.98 0.83 0.64 0.63 0.49 0.55 0.43 45
40 2.08 1.48 1.39 0.99 0.90 0.64 0.69 0.49 0.60 0.43 40
20 2.60 1.56 1.73 1.04 1.13 0.68 0.86 0.52 0.75 0.45 26
0 3.72 1.64 2.48 1.09 1.61 0.71 1.24 0.54 1.07 0.47 -162
-20 5.02 1.56 3.35 1.04 2.18 0.68 1.67 0.52 1.45 0.45 8


Table: Beam sizes for configuration AB
Dec. 100 GHz 150 GHz 230 GHz 300 GHz 345 GHz PA
  Maj. Min. Maj. Min. Maj. Min. Maj. Min. Maj. Min. $^\circ$
80 1.20 0.98 0.80 0.65 0.52 0.42 0.40 0.32 0.34 0.28 35
60 1.15 0.90 0.77 0.60 0.50 0.39 0.38 0.30 0.33 0.26 48
40 1.19 0.88 0.79 0.58 0.51 0.38 0.39 0.29 0.34 0.25 46
20 1.32 0.90 0.88 0.60 0.57 0.39 0.44 0.30 0.38 0.26 35
0 1.65 0.95 1.10 0.63 0.72 0.41 0.55 0.31 0.48 0.27 23
-20 2.44 0.92 1.63 0.61 1.06 0.40 0.81 0.30 0.71 0.26 10


Table: Beam sizes for configuration A
Dec. 100 GHz 150 GHz 230 GHz 300 GHz 345 GHz PA
  Maj. Min. Maj. Min. Maj. Min. Maj. Min. Maj. Min. $^\circ$
80 0.99 0.75 0.66 0.50 0.43 0.32 0.33 0.25 0.28 0.21 26
60 0.97 0.71 0.65 0.47 0.42 0.31 0.32 0.23 0.28 0.20 35
40 1.04 0.70 0.69 0.46 0.45 0.30 0.34 0.23 0.30 0.20 33
20 1.19 0.70 0.79 0.47 0.51 0.30 0.39 0.23 0.34 0.20 27
0 1.55 0.72 1.03 0.48 0.67 0.31 0.51 0.24 0.44 0.21 20
-20 2.31 0.68 1.54 0.45 1.00 0.29 0.77 0.22 0.66 0.19 10

Figure: uv-plane coverage and beamshapes for the D and CD (7 antenna) configurations. Contour levels are at 5%, 10%, 20%, and 50%. Frequency is 100 GHz.
\includegraphics[height=.9\textheight]{noema-intro-config-d} \includegraphics[height=.9\textheight]{noema-intro-config-cd}
Figure: uv-plane coverage and beamshapes for the BCD and BC (7 antenna) configurations. Contour levels are at 5%, 10%, 20%, and 50%. Frequency is 100 GHz. Note the different scaling of the uv-plane with respect to Fig. [*].
\includegraphics[height=.9\textheight]{noema-intro-config-bcd} \includegraphics[height=.9\textheight]{noema-intro-config-bc}
Figure: uv-plane coverage and beamshapes for the AB and A (7 antenna) configurations. Contour levels are at 5%, 10%, 20%, and 50%. Frequency is 100 GHz. Note the different scaling of the beam maps with respect to Figs. [*] and [*].
\includegraphics[height=.9\textheight]{noema-intro-config-ab} \includegraphics[height=.9\textheight]{noema-intro-config-a}


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Gildas manager 2015-03-01