REU UW-Madison

Eric Wilcots' Homepage

WWU Physics

                        What I Actually Did:

step 1 : flagging the data

     Before Flagging                                            After Flagging

Before the data may be used it must first be flagged. If you examine the picture on the right you will notice a vertical line of signal. This corresponds to a time when all of the pointings of the dishes are not aligned and so there is leakage and is not actual data. Before analyzing the data it was necessary to go through and delete all such 'messy' signals. That way only the real data is actually used in the scientific evaluation. This can be very time consuming.

Step 2: Calibration

There are three types of calibration which must be performed.

The primary calibrator (the first and brightest source above) is used to determine the amplitude and flux bandpass calibrations. This takes into account instrumental effects of the specific telescope being used.

The secondary calibrator (the third and second brightest source above) is used for phase calibration. This calibrator must be located close to the source as it takes into account changing atmospheric conditions.

Step 3: Cleaning and Restoring

     Sidelobes: while most of the detected flux from a given source will go into the main detection, a certain percent will go into sidelobes. How much is a function of the interferometer. These sidelobes appear in the data as rings surrounding the source:

  During the cleaning process these rings are recognized as belonging to the source and the data made to reflect that fact:

Above: three different channels shown both before and after the cleaning process.

Step 4: Data Analysis

    This is when moment maps, various graphs, and models were created in order to analyze the data. To see the final results, click on IC5332 below.

The moment 0 map shows all of the HI in IC5332 integrated over velocity.