Create the input file lists

When we looked at the archive we identified the data that were needed. Now we can create input file lists that we will feed to the IRAF tasks. We do that rather than having to type all the input files again and again. Using lists will also allow us to automated several tedious bookkeeping tasks later on.

Gemini IRAF offers a task to help us create those lists: gemlist in the package gemtools. Let’s do it.

Change to redux directory

Make sure you are in the redux directory. This is where we work from now on.

cd /your/work/directory
cd redux

Biases

Going through the archive, we found that these raw biases are a good match for our data. We will use all these to make the master bias S20060314S0091_bias.fits.

Biases
S20060314S	91-93
S20060322S	157-161
S20060330S	58,60-62
Processed bias name: S20060314S0091_bias.fits

The list is created from that information as follow

gemlist S20060314S 91-93 > bias.lis
gemlist S20060322S 157-161 >> bias.lis
gemlist S20060330S 58,60-62 >> bias.lis

Standard Star

Normally, there’s only one exposure taken for the standard star. For some reason, in this case, four were taken. After reducing them, it was found that they are all well exposed so anyone of them could be used. The third one is used in this tutorial simply because it is the one with the best signal.

In this tutorial, we do not cover the reduction of the standard in the interest of time. Though we will show how to get the sensitivity function from the reduced standard star.

For an overview of the standard star reduction, see the diagram in Appendix 1, Standard star.

From the archive search, we found these data for the standard star and its calibration files.

Standard Star
Std Star	S20060331S	53-56
Flat	S20060331S	57
Arc	S20060329S	45
Produced sensitivity function: ltt4364_629_20060331_sens.fits
In this tutorial the sensitivity function is derived from S20060331S0055.fits.

Because we will not reduce the standard star and rather just focus on the steps specific to the sensitivity function, this is the only list we will need:

gemlist S20060331S 55 > std.lis

If you were to reduce the standard star fully, you would create a list for the flat and for the arc, like we do below for the science data.

Science Exposures

In the table below is a subset of our source’s observation sequence. We will work with only two cubes. In fact, in the interest of time we will reduce only one, the second is already reduced and provided to you for the last step, the cubes stacking.

We use lists for the science exposures, which makes sense since normally we do reduce several exposures, but we will use lists for the single flat and the single arc too. The idea is to keep the data reduction commands as generic as possible to simplify re-use of these instructions. If you want to use the instructions for your data, just generate the appropriate lists and for most commands, there won’t be a need to modify anything.

Science Observation
Science	S20060327S	43
Flat	S20060327S	44
Arc	S20060329S	45
Using bias: S20060314S0091_bias.fits
Using sensitivity function: ltt4364_629_20060331_sens.fits

Generate the lists.

gemlist S20060327S 43 > sci.lis
gemlist S20060327S 44 > flat.lis
gemlist S20060329S 45 > arc.lis

We are now good to go!

Note

In PyRAF programming syntax, the gemlist call would look like this: iraf.gemlist('S20060327S', '43', Stdout='sci.lis'). This syntax is used when wrapping with Python, or when wanting to use variables. We will be using that syntax for the rest of the tutorial.