KMOS Reduction Steps¶

These are my steps for reducing KMOS data

1. Download data from ESO¶

Unzip the data:

$ gzip -d *.Z

If you want to inspect the final data you can use:

$ dfits –x 0 KMOS*fits | fitsort tpl.id det.seq1.dit ins.filt1.id ocs.rot.naangle

Note

May need to correct bias from detector readout (causes striping in raw images), with code from Trevor Mendel (but I think this is fixed in recent versions of the ESO pipeline)

2. Run EsoReflex¶

esoreflex &

I use the following settings:

Remove the COMBINE step so that all OBs can be combined later
SCI_RED ==> sky_tweak = true
Set UseSkyFlats = no (to use lamp flats instead - taken at more rotation angles, better according to ESO)
Animate at runtime 100ms

3. Sky subtraction correction¶

Do additional sky subtraction correction to individual exposures

Note

ESO pipeline v<1.4 may need to do flux calibration correction, to divide by DIT length. Can use kmos_tools.pipeline_fixes.flux_fix().

import kmos_tools as kt

# Find your individual exposures
exp_list = kt.find_exposures(prefix='*', dir='*/')

for exp in exp_list:
        frame = kt.Exposure(exp)

    # Make 1D sky residual spectra for each exposure (1 per detector)
    kt.make_sky_residual_spectra(frame)

    # Do additional sky subtraction and save
    kt.subtract_sky_residual_spectra(frame)

Note

I also had some success with ZAP. however it had problems at the edges of the cubes.

4. Rotate frames which don’t have North up (optional)¶

Sometimes the instrument is rotated between OBs, need to rotate the IFUs so they can be combined

import kmos_tools as kt

# Find your individual exposures
exp_list = kt.find_exposures(prefix='*', dir='*/')

for exp in exp_list:
        frame = kt.Exposure(exp)

    kt.rotation_fix(frame)

5. Measure star PSFs and calculate user shifts¶

Use observed stars in each exposure to estimate the PSF and then calculate a list of accurate dither offsets between exposures (as KMOS doesn’t always go where you set the dithers…)

5.1. Find positions of stars¶

Finds stars in exposures, measures their PSF FWHM and positions and creates a list of the ‘good’ frames (below a PSF cut) and a table of the star positions.

# List of frames to check (should be all the frames you want to combine)
frame_list = ['frame1.fits', 'frame2.fits']

fname_stars   = 'stars.txt'   # File to save star parameters to
fname_combine = 'combine.sof' # .sof file to create

kt.star_positions_batch(frame_list, psf_cut=0.8, star_ifu=None, starparams_filename=fname_stars, combinefiles_filename=fname_combine)

Note

The code tries to find stars in the exposures by looking for star in the target name of the IFU (HIERARCH ESO OCS ARM# NAME header value). You can set it manually by setting star_ifu to the relevant IFU number.

5.2. Calculate shifts between frames¶

Using the fname_stars file, calculate the shifts between each frame.

fname_usershifts = 'usershifts.txt' # file to save usershifts to

kt.make_user_shifts_file(starparams_filename=fname_stars, usershifts_filename=fname_usershifts)

Note

If using user shifts to combine KMOS frames, the order of frames in .sof must match the order of the offsets in 'usershifts.txt'. This should be done automatically in these scripts, so don’t reorder the frames in the .sof file.

6. Combine exposures¶

I use the default (sigma clipping) combination, using my calculated shifts between frames

Note

In v1.4 combine.sof file needs SCI_RECONSTRUCTED after filename

combinedir=combineOBs
mkdir $combinedir
cp usershifts.txt combine.sof $combinedir
cd $combinedir
esorex kmos_combine ==method='user' ==filename='usershifts.txt' ==edge_nan combine.sof