Observational Techniques: Assignment 1
Aims
The aim of this assignment is to teach you how to carry out a very common programming
task: reading in a bunch of data from a text file, doing something with it then writing
the results out again.
It's also a chance to practice the celestial coordinates and brightness scales things we learned
in the first lecture.
Your Mission, should you choose to accept it
You have an observing run coming up on the AAT. You wish to observe a sample of micro-quasars.
The goal of the assignment is to write a computer program which will select this sample for you.
You will pick the micro-quasars to observe from a rather large catalogue, which can be found
here:
The catalogue is an ASCII (text) file - you can inspect it with a normal text editor. It contains
the following columns:
- Catalogue number of the micro-quasar.
- Equatorial coordinates of the micro-quasar. This consists of six numbers, the Right
Ascension (hours, minutes and seconds), followed by the Declination (degrees, minutes and
seconds)
- The B-band magnitude (all magnitudes are Vega magnitudes)
- The K-band magnitude
- The radio flux (21cm wavelength) in mJy.
You want to pick out the best targets to observe from this catalogue. To be a good target, a
micro-quasar must pass the following two tests:
- It must be in a part of the sky that is accessible during your observing run. Your run is
on 19th - 23rd March, and is at the AAT (latitude -31).
- You want to pick micro-quasars which are abnormally bright at radio wavelengths. The
standard theory suggests that the spectrum of these sources should be a power law: i.e.
flux per unit wavelength proportional to wavelength raised to some power. You should use the B and
K magnitudes to work out what this power-law is. The best targets are those whose radio (21cm) flux
lies as far as possible above an this power-law (extrapolated from the B and K magnitudes).
In principle, you could just go through the catalogue manually and pick out the best sources. But
the catalogue is very large - it contains 50,000 entries. Thus to find the best targets, you will
need to write a computer program.
What to Submit
The submission deadline is mid-day on Thursday 19th April. You should submit two things (by
e-mail to me):
- A copy of your computer program.
- A list of the ~50 best targets. This is somewhat subjective, so everyone's list will
likely be a little different, which is fine.
Example Programs
To get you started, here is a simple example program which does many of the basic tasks
you will need to solve this problem:
To run the program you will need to put a data file called data.d in the same directory: here is
a suitable data file.
You may (or may not) also be interested in the program which I wrote to generate the synthetic
micro-quasar catalogue. It's not really relevant to this assignment, but some of the things I
do in this program will be very relevant in future assignments.
I will be in my Stromlo office on Monday and Thursday morning if you'd like help with writing
this program. Otherwise you can contact me by e-mail.