Memorandam of the discussion on FMOS observations and data kicked off by Ian Lewis Masayuki Akiyama 14 January 2004 FMOS Science Workshop

Memorandam Format Issues listed by Ian Lewis –Detailed descriptions –Questions raised Possible solution or answer

Observation Modes Standard star observations –Do we need individual observation for a standard star ? Yes, potentially. Alternative is assign a few fibres to A,F-stars in FOV Stare mode –10-15 fibres on sky: determin mean sky with the fibres and subtract the mean sky from object spectra Beam switching 1 (simple: obj-sky ) Beam switching 2 (double-beam: pairs of fibres with obj- sky and sky-obj) –What is the best timescale for the switching 15min? 30min? Check with the real sky during comissioning Out of focused bright star

Observation Data Types Normal (stare and beam switch) Standard star observations Calibration arcs Flatfield image Throughput mapping (on sky) Slit dither with flat-field lamp illumination –Purpose : Measure pixel-to-pixel sensitivity variation of detecter

Detector calibration ( Individual data frame preprocessing) Dark current Flat-fielding Hot/Dead pixels Cosmic rays Fringe ? How serious ? Electrical cross-talk ? –Especially, for a bright star for atm. Abs. Calibration. Linearity Memory from bright light source ?

Fibre Flat field Image Calibrate spectrum location (tramline mapping) Scattered light measurment Different illumination –The light pass for the flat-field light is different from that of the objects.

Dithered Flat field Image Different illumination –The light pass for the flat-field light is different from that of the objects.

Arc Calibration Wavelength –OH lines are not uniform in wavelength direction, masked out – Residual OH lines can be used... PSF difference between fibre to fibre –Ar-lamp has different illumination from target light

Throughput mapping Must be done on sky (with fibres in correct configuration due to spine tilt effects) –15% loss at edge of the field with maximum tilt –flat field lamp : different illumination Sky lines missing (OH suppression) –move slit unit to recover masked O2 line can be used at 1.7micron We need to take flat-field data for all configuration to calibrate loss due to fibre entrance tilt

Data reduction Data extraction Frame combination Flux calibration A,B beamswitch addition Header information –2dF data pipeline.

Revision of 2dFdr FMOS specific issues –IR-array large pixel-to-pixel variation : flat-field before extraction flat caribration in lab? –beam-switching –flux and absorption calibration Alternative software development in UK? Gavin

Implementation? Data analysis during observation –Purpose : Quality control : feedback –IR-array : Non-destructive read out during exposure ? CIRPASS Final data reduction –No...Big survey Automated pipeline Semi-automated pipeline (e.g. 2dFDR) Independent tasks

Additional Issue Input Catalog Accuracy – ” is sufficient, and already achived ? Slit-gap between J and H band spectra