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2dfdr Data Reduction Software


2dfdr is an automatic data reduction pipeline dedicated to reducing multi-fibre spectroscopy data (with current implementations for AAOmega with either the 2dF or SPIRAL IFU top ends, 2dF, 6dF, FMOS and the older Spiral). A graphical user interface is provided to control data reduction and allow inspection of the reduced spectra. It is being continually developed at the AAO in response to user feedback. You can reduce most of your data by simply pressing START AUTO REDUCTION in the Graphical User Interface.

Contents:

Current Version


As of August 2012 - 2dfdr version 5 is now available. The software has been improved to make it easier to use and more robust. However, please note that development work is continuing so please let us know if you experience issues.

The software can be downloaded from the ftp site ftp://ftp.aao.gov.au/pub/2df/. The software is distributed as an executable binary and is available for Linux and Mac operating systems.

Installing and Running 2dfdr


See the 2dfdr CookBook to get started. Users familiar with 2dF data reduction may still benefit from a quick look at this, which highlights the operational changes.

An up-to-date manual is in development and will be broadly announced to the community when it is completed.

Guide to AAOmega File Format


A description of the 2dfdr file format is given in the guide to the 2dfdr file format.

Guide to modifying the wavelength solution with 2dfdr


Occasionally it is necessary to modify the wavelength solution obtained with 2dfdr. Strategies for this are given in the guide to modifying the wavelength solution with 2dfdr.

Frequently Asked Questions


Questions:


Answers:


Is it possible to look at the data after each reduction step in drcontrol?

One can turn on various automatic plot options - the fitted tramlines, the fit to the scattered light background and the profile fits during extraction (with the FIT method), the throughput map and the subtracted sky under the plot tab. If you want to look at the raw extracted spectra (i.e. before calibration/sky-subtraction) use the plot tab to look at the *ex.fits files after reduction.

How does the emission-line throughput calibration work in drcontrol?

All sky lines are used. Sky-line pixels are identified by plotting the wavelength derivative of the flux - those with large derivatives are identified as sky-emission-line-pixels. Obviously if your wavelength range contains no sky lines (e.g. at high-dispersion in the blue) this option should not be used! In that case twilight flats and offset sky frames will be needed. Note, it is only possible to do twilight flats for a maximum of 4 fields a night, two at the start and two at the end, since the fields must be pre-configured in order to take twilight flats, and the flat is not relevant once fibres have been moved, even if the field is reconfigured at a later date.

What does flat-fielding mean in drcontrol?

There are three-meanings. The first is the dispersed white-light fibre spectra used to fit the tramlines. This is what is usually referred to as the `FLAT'. The second meaning is `pixel-to-pixel CCD flat field' otherwise known as a 'longslit flat'. The third meaning is `fibre flat-field' by which we mean dividing the extracted object spectra by extracted, normalized, white light spectra (this is usually the same as that used for the tramlines). Given the uniformity of modern CCDs the work of the 'longslit flat field' can be done with the 'fibre flat'.

How can one omit 'sky' fibres which contain objects in drcontrol?

Normally this should not be necessary as drcontrol takes a median sky, and clips outliers. If you really must, create a file called `skyfibres.dat' in the working directory, listing the numbers (one per line) of the fibres you wish to use for sky. drcontrol will then use this file, in preference to the headers, when you reduce (or re-reduce) the data.

How does 2dfdr handle flexure?

AAOmega is a bench mounted spectrograph in a stable thermal environment. During commissioning, when the spectrograph had not yet reached thermal equilibrium, a small shift of the spectra on the CCD was seen at the 0.5 pixel level. To retain the possibility of correcting for this the "shift and rotate" option allows the tramline map to be tweaked to the data. Shifts have not been seen to be an issue to date. However, if shifts are seen to be a problem for a data set, additional arc frames would be needed during an observation, rather than the single arc taken at the start of each new field.

Can one save drcontrol parameter settings?

No, but you can create .idx files with these settings preset.

Can one combine frames BEFORE sky subtraction in 2dfdr?

No. If you want to experiment with this turn sky-subtraction off completely and do your own processing on the final individual spectra. If you get better results that drcontrol, let us know. Most previous efforts at this have failed, and AAOmega has been seen to give 1% sky subtraction, if you care at this level then ask your support astronomer about "Nod and Shuffle" observations.


Bug reports about 2dfdr should be addressed to the AAOmega team.


Sarah Brough (sb@aao.gov.au)