In
interferometry
Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...
, the zero spacing flux (ZSF) refers to the estimated integrated
flux density
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phenom ...
within the
field of view
The field of view (FOV) is the angle, angular extent of the observable world that is visual perception, seen at any given moment. In the case of optical instruments or sensors, it is a solid angle through which a detector is sensitive to elec ...
of an interferometer that would be measured by a (potentially hypothetical) single-dish
telescope
A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...
possessing the same
primary beam as the interferometer. This value does not represent a direct measurement, but rather an extrapolation based on both single-dish observation and interferometric data. Sometimes, in place of single-dish observations, dense array configurations can be used to capture large-scale emission data.
The ZSF plays a crucial role in the construction of accurate images of astronomical sources, especially those that are extended across the field of view. Because interferometers cannot directly measure visibilities at zero separation between antennas (zero baseline), the ZSF remains unknown. This missing information can lead to a phenomenon known as the "missing flux problem." In the reconstructed image, extended sources appear to be surrounded by a faint, negative halo of brightness.
By merging single-dish observations with the interferometric data, astronomers can account for the flux density of the largest structures in the sky, which are not captured by interferometers due to their limited spatial resolution.
See also
*
CLEAN (algorithm)
References
External links
The problem of short spacings*
Multi-element vertical array for zero-spacing interferometry'
Interferometry
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