1. Astronomy 920 Commissioning of the Prime Focus Imaging Spectrograph
Meeting 7
SALT IRAF Package
Ken Nordsieck
Oct 21, 2005
Ast 920 Meeting 7

2. PFIS First Light Night NGC 1866 (LMC) 6290 Interference Filter 5 sec
Oct 21, 2005
Ast 920 Meeting 7

3. Why did we go to all that expense to get large diameter etalons?
Quiz Question
Why did we go to all that expense to get large diameter etalons?
Oct 21, 2005
Ast 920 Meeting 7

4. Scanning
PFIS control system allows arbitrary sets of discrete steps (equal exposures)
linear scan for line profiles
dithering onto continuum for absorption lines
Off axis, must take account of wavelength gradient due to cos θ
center to edge gradient:
λ(r)/ λ0 = 1/ cos θ ~ ( *(r/4’)2 ) (24 Ang at Hα)
Inside “bullseye”, wavelength changed by less than resolution:
D(bullseye) = 1.4’ (10,000/R)1/2
- if object larger than bullseye, extend scan to cover same wavelengths
- if object not round, pays to move telescope and rescan, instead of extending scan
Oct 21, 2005
Ast 920 Meeting 7

5. Accessing SALT IRAF package
Source (environment variable $salt)
Unix: /usr/local/salt
MAC: /usr/local/iraf/irafext/salt
cl> salt [ loads salt task ]
cl> help pfis [ lists pfis commands ]
cl> pfis [ loads pfis subtask ]
cl> cd working directory/yyyymmdd
Oct 21, 2005
Ast 920 Meeting 7

6. PFIS/ SALT IRAF Package Hierarchy
PFIS commands
PFIS/ SALT IRAF Package Hierarchy
implemented
lower level
pprepare p pireduce r pmosaic m imcoadd
pgain pbias psreduce ps pstransform t psskysub s psextract e scombine
piflat psflat pswavelength pscalibrate c psstandard
pbpm pscut
Raw data
name: Pyyyyddddssss.fits, ie P fits
"multiextension" fits file, one for each of 6 amplifiers; open in DS9 with "open other/ open mosaic IRAF"
Each stage of processing prepends a letter or two
Imaging: (pireduce, pmosaic) mrpP fits
Spectroscopy: (psreduce) psP2.....
Oct 21, 2005
Ast 920 Meeting 7

7. Imaging pprepare (p) pireduce (r)
check header validity,
get data from calibration database
pireduce (r)
remove crosstalk
subtract mean of overscan in each amp, trim
divide by gain for each amp
subtract bias, if specified
subtract dark, if specified
divide by flat, if specified
pbias: run pireduce on bias frames, bias/ dark/ flat turned off
pflat (TBI) run pireduce on flat frames, dark/ flat turned off
pmosaic (m)
combine amplifiers and ccd's into single fits files
can now be opened as normal image by DS9
imcoadd (TBI)
remove distortion
combine mosaiced images, registering and removing cosmic rays
Oct 21, 2005
Ast 920 Meeting 7

8. Spectroscopy psreduce (ps)
run pireduce
run pmosaic
using slitmask definition file (MDF), cut into one piece for each slit (pscut)
apply first guess wavelength calibration to each
psflat (TBI) run psreduce on spectral flats (tungsten continuum spectrum)
pswavelength identify lines and update wavelength dispersion calibration for wavecal frame
pstransform (TBI) resample cut spectra onto linear wavelength vs space grid
psskysub, psextract (TBI) extract to 1-d raw spectra
pscalibrate compute flux cal from flux standard
Oct 21, 2005
Ast 920 Meeting 7

9. Configuration Data
Instrument configuration data: $salt/pfis/data (IRAF pfis$data)
PFISamps gain and noise for ccd amps
PFISxtalk crosstalk coefficients
PFISgeom orientation of CCD's in mosaic
PFISdistortion correct pincushion distortion of collimator (r ~ R + AR3 + BR5)
PFISfilters. filter list with pointers to transmission curves in /filters
PFISgratings. grating list with alignment calibration
/masks. mask definition files
/linelists. linelists for calibration lamps: Xe, Ne, HgAr
Oct 21, 2005
Ast 920 Meeting 7