Amplitude Analysis

There are two tasks in Miriad uvamp and smauvamp allowing users to perform amplitude analysis in the UV domain. The algorithm used in uvamp differs from those used in smauvamp although both of the programs are for amplitude analysis of visibility data and/or models.

uvamp performs vector average in each of the binned annular rings in a uv-plane and allows users to shift source center to the phase center. uvamp is good for a source/model with annular symmetrics such as a point source, a circular disk, a ring and etc.. Here is the usage for running uvamp to plot the amplitude versus UV distance:

uvamp vis=vis_1,vis_2,vis_3,...,vis_n bin=30,4,nsec device/xs

The data can be taken from multiple visibility files (visi_1,vis_2,vis_3,...,vis_n). The data are divided into 30 bins along the axis of the uv distance with a bin interval of 4 nsec.

smauvamp bins the data along the x-axis (time,uvdistance, uc,vc and etc.) selected by users. smauvamp does the vector average of the baseline-based visibilities in a time interval selected by users prior to performing the statistics in each bin. Both the vector averaging and bin statistics are weighted by the visibility variances. Instead of shifting the phase center, smauvamp allows users to rotate the uv plane to match the v-axis to a desired direction. smauvamp is good for sources with axis symmetrics (such as a point source, two point sources - sinusoid beating, an elongated guassian source, an elliptical disk and etc.). smauvamp also allows users to plot time variability with proper statistics in a uv-range dominated by a point source.