Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/people/Julie.Grant/astrotech/Radio-project.pdf Дата изменения: Tue May 13 05:14:04 2014 Дата индексирования: Sun Apr 10 09:44:42 2016 Кодировка: Поисковые слова: apollo 11

Astronomical Techniques Project 2 Radio Astronomy Continuum Imaging

Due 19 May 2014 5pm

The data for this project will be made available in class on Tuesday 13 May and online. During the second half of class on Wednesday 14 May instructions and examples on how to make radio continuum images in CASA will be provided. This will provide you with the information to complete this assignment. Prior to class on Wednesday 14 May, please install CASA onto your computer. The software can be found here: http://casa.nrao.edu/casa_obtaining.shtml Understanding radio observations We will be imaging 3C129. Have a look at the observational summary to answer the following questions: 1. What is the wavelength/frequency observed? 2. What is the source coordinates? 3. How many antennas are working? Plot the locations of the antennas for this observation. The uv-plane Now examine the uv-plane to gather information on what the radio source will look like once imaged. 1. Plot the uv-plane for the observations. 2. How would the uv-plane look if there were only 1 scan of the source? 3. How would it look if there were only 3 scans of the source? 4. What is the shortest baseline in these observations in metres? Which antennas make up these baselines? What angular scale does that correspond to? 5. What is the longest baseline in these observations in metres? Which antennas make up these baselines? What angular scale does that correspond to? 6. What is the resolution of these observations? This is also known as the synthesised beam size. Making continuum images We will make an image from these observations. The first step is to make a dirty image and then clean the image. 1. Choose an image size and pixel size that would suit the image and explain how you came to these values. 2. Create a Stokes I image of the radio source using all available data. Clean with niterations=200 then 3000. What is the difference? Does the noise level change? What happens to the sidelobe patterns? 3. Create a low resolution and a high resolution Stokes I image of the radio source. Explain how you chose what baselines to use. What is the difference between the two images? 4. Create a Stokes I image of the radio sources after removing the data from the antennas on the East arm. How does this image compare to the image created in step 2? 5. What are the benefits of each image and what science could be done with each image?