Radio Interferometric Imaging of Virgo A (M87) with the allen telescope array

Manager: adrian lam

contact: adrianlam0ho@g.ucla.edu

Learning Objectives:

• Theory and practice of interferometric imaging in radio astronomy
• Digital signal Processing
• Image processing
• Scientific computing with bulk astronomical data
• Planning and executing an observation on a professional radio telescope array (!)

Recommended Preparation

• Programming experience in Python or C++ is preferred (e.g Physics 4AL/BL, CS3x, PIC10x). If you are relatively new to python, this is a great tutorial to get started: https://cs231n.github.io/python-numpy-tutorial/. Most of the coding in this project will be done in Python (e.g. Numpy, Scipy).
• Basic knowledge in astronomy (e.g. Astro 81) and Signal Processing is helpful but not
necessary.

Background

Radio Interferometry is an observation technique designed to produce astronomical
images of unprecedented resolution. An important application of radio interferometry is
the imaging of extremely small objects, a famous example being the M87
supermassive blackhole imaged by the EHT in 2020.

Image 1: The M87 supermassive blackhole. Credits to The Event Horizon Telescope Collaboration

In a single telescope, the resolution of an image is ultimately limited by its size, known
as the diffraction limit. In essence, radio interferometry works by combining the
individual observations from many (i.e. an array of) smaller telescopes. In a radio
interferometer, the final image resolution is then limited by the size of the telescope
array, instead of the individual telescopes. This technique is known as aperture
synthesis (https://en.wikipedia.org/wiki/Aperture_synthesis). To illustrate the difference,
the M87 blackhole image has a resolution equivalent to an Earth-sized telescope!

Project

In this project, we will perform interferometric imaging with the Allan Telescope Array
(ATA) to image Virgo A, an extragalactic radio source with a characteristic jet originating
from the aforementioned M87 supermassive blackhole.

The imaging experiments will be carried out on the Allan Telescope Array (ATA), a 42-
element array of 6.1m radio telescopes.

The project is a collaboration between our team, the GNU Radio community and the
SETI Institute. In particular, our work will be built upon the existing work of the GNU
Radio community. Thanks to our generous collaborators, we will be allocated
observing time on the ATA for the imaging experiment. Our team’s main task is to
process the raw telescope data to produce the final Virgo A image.

The project has 2 main milestones: The first milestone is to utilize our collaborators’
existing software stack to process the observation data, producing the Virgo A image.
The second milestone is to make improvements to the existing software pipeline.

Image 2: Radio imaging of Virgo A by the VLA, showing the famous one-sided jet. Note that the M87 galaxy itself and its blackhole are too small to be visible in the image. The M87 galaxy is located at the center tip of the jet, while the supermassive blackhole is located inside the active galactic nucleus. [Credits: ESA]

Logistics (tentative)

  1. Timeline:
    • Virgo A Observation: Winter Quarter 22
    • Data Processing: Winter — Spring Quarter 22
  2. Time commitment: upto ~5 hours/week (flexible during midterm/final weeks, of course). 1-2 work meetings per week. (Optional) Possible field trip to the ATA during the observation weekend

Additional Resources

Here are some resources to get started on Radio Interferometry:

  1. Gentle Introduction to interferometry (Credits to Neal Jackson, ESA)
  2. Lectures about Interferometry (Credits to Oleg Smirnov, SKA SA)