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The point source sensitivity (one
level) for an
antenna array, over a bandwidth
in a time
is given by
 |
(1) |
where
is the antenna efficiency (Jy K
) i.e.
with
the aperture
efficiency,
the antenna collecting area, and
the Boltzmann constant (22 JyK
at 85 GHz, 29 JyK
at
150 GHz, 35 JyK
at 230 GHz and 45 JyK
at 350 GHz). These factors were determined for stable atmospheric
conditions.
is the system temperature outside the atmosphere, i.e. corrected for atmospheric
transmission (typically 100 K below 110 GHz, but 180 K (170 K) at 115 GHz, 150 K (130 K) below 150 GHz, 200 K (170 K) above 150 GHz,
250 K (200 K) at 230 GHz, and 500 K (370 K) at 350 GHz in summer (values in brackets are for typical winter conditions)).
is a measure of the instrumental and atmospheric decorrelation coefficient, related to the oscillator phase jitter and
the atmospheric phase noise, respectively. The instrumental phase jitter increases linearly with frequency. The short and long term
atmospheric phase fluctuations depend on the baseline length and water vapor content of the atmosphere. Typical summer (winter) values
for
are 0.9 (0.9) in band 1, 0.8 (0.85) in band 2, 0.6 (0.8) in band 3, and 0.5 (0.7) in band 4.
is the noise equivalent bandwidth of the correlator in Hz, equal to 1.88 times the channel separation; the effective channel
width for standard apodization (using a Welch time-lag window) is 1.60 times the channel separation,
is the on-source integration time per configuration in seconds (2 to 8 hours, depending on source declination).
Because of various calibration observations, the total observing time is typically 1.6
, and
is the number of polarizations: 1 for single polarization and 2 for dual polarization (see Sect.
for
details).
Assuming typical summer conditions at the NOEMA site, 6 antennas, an integration time of one hour in a 3.6 GHz bandwidth and using both polarizations, we find point source sensitivities
of 0.09 mJy at 90 GHz, 0.19 mJy at 150 GHz, 0.52 mJy at 230 GHz, and 1.61 mJy
at 300 GHz. For a full synthesis (e.g., 2 configurations or 10 hours on source), this goes down to about 0.03 mJy, 0.06 mJy, 0.18 mJy,
and 0.51 mJy, respectively.
Next: Mapping
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2015-03-01