1. Long-Slit Spectra Reduction with IRAF

2. l Arp 63 Fig.1: Galaxy + slit Fig.2: Galaxy spectrum
Fig.3: Star spectrum

3. Bias subtraction noao.imred.ccdred zerocombine ccdproc / imarith
Frame - <bias>
Fig.4: Bias image
imstat
# IMAGE NPIX MEAN MIDPT STDDEV MIN MAX
Zero

4. Flat-field correction
noao.imred.ccdred
flatcombine
ccdproc / imarith
Frame - <bias>
<flat> - <bias>
Fig.5: Flat image
imstat
# IMAGE NPIX MEAN MIDPT STDDEV MIN MAX
Flat

5. Flat-field normalization
noao.twodspec.longslit
response
Fig.6: Flat-field fitting along dispersion
Fig.7: Normalized flat
imstat
# IMAGE NPIX MEAN MIDPT STDDEV MIN MAX
nFlat

6. Cosmic-rays removal noao.imred.ccdred cosmicrays crutils crmedian
Fig.8: Spectrum after bias and flat correction

7. L.A. Cosmics (Van Dokkum, 2001)
Fig.10: Cosmic-rays mask
Fig.9: Spectrum with cosmic-rays
Fig.11: Cleaned image

8. Wavelength calibration
noao.twodspec.longslit
identify
reidentify
fitcoords
transform
Fig.12: Helium-Argon lamp spectrum

9. li = 4458.3 Å dl = 2.6 Å/px Fig.13: Spectral lines identification
Fig.15: Bidimensional fit
li = Å
dl = 2.6 Å/px
Fig.14: Fit residuals

10. Checking calibration Fig.17: After calibration
Fig.16: Before calibration
Fig.17: After calibration
Fig.18: Night-sky [OI] lines

11. Flux calibration noao.twodspec.apextract apall noao.onedspec standard
sensfunc
noao.twodspec.longslit
calibrate
Feige 56
Fig.19: Standard star spectrum

12. Fig.20: Star profile across dispersion
Fig.21: Tracing along dispersion
Fig.22: Extracted 1-D spectrum

13. counts erg cm-2 sec-1 Å-1 Fig.23: Star fluxes measurement
Fig.24: Calibration curve (upper)
erg cm-2 sec-1 Å-1

14. Frame ------------- calib. func.
Fig.25/26: Before and after flux calibration
Frame
calib. func.
Fig.27: Calibrated spectrum (red)

15. Night-sky subtraction
noao.twodspec.longslit
background
Fig.28: Fit of the sky across dispersion
Fig.29: Spectrum after sky subtraction