Next Generation Very Large Array Memo #122: Characterization of the synthesized beam with and without MID antennas in Mexico

TL;DR

This study analyzes how the inclusion of MID antennas in Mexico affects the synthesized beam quality of the Next Generation Very Large Array, showing significant improvements in beam properties when antennas are present.

Contribution

It provides a detailed comparison of synthesized beam characteristics with and without MID antennas, highlighting the impact on beam ellipticity and resolution for different configurations and declinations.

Findings

Beam ellipticity increases by at least 1.3X without antennas.

Including MID antennas improves beam performance, especially for southern sources.

Larger tapering reduces ellipticity but affects resolution.

Abstract

Synthesized beam (PSF) synthetic observations with and without the antennas in Mexico are analyzed. For a simple continuum observing setup, we generated visibility files and their associated PSF images for a grid of parameters (robust weighting, tapering, and declination). The tests were done for both the MID and MID+Spiral+Core configurations and their cropped versions without antennas in Mexico. We show that the performance of the Array, in terms of the beam properties, is in general significantly better when both the MID array antennas are present in Northern Mexico and observations target southern sources. At a declination of -40 deg, there are increments in the ellipticity of at least ~1.3X and 1.2X for a tapering of 3.0 and 4.0 mas, if the antennas in Mexico are not included. For the parameter space tested, the changes in ellipticity of the MID and MID+Spiral+Core configurations differ by ~10%. Larger tapering values help to reduce the ellipticity for cropped configurations at all declinations, but it will impose more constraints in terms of angular resolution.