Testing Galfit

1
Testing Galfit

• Clemens Trachternach1, Olaf Schmithüsen1, Gijs
  Verdoes Klein2, Ewout Helmich2, Dominik Bomans1
  ,Ralf-Jürgen Dettmar1, Oliver-Mark Cordes3,
  Thomas Erben3, Hendrik Hildebrandt3, Patrick
  Hudelot3,

1Astronomisches Institut, Ruhr-Uni
Bochum 2Kapteyn Instituut, Rijks-Universiteit
Groningen 3Argelander Institut für Astronomie,
Uni Bonn
2
CFHTLSCanada France Hawaii Telescope Legacy
Survey

• 36 CCDs
• 1 deg² FoV
• 1.2hr exposure time in i-band
• MagZP 25.75 mag
• Seeing 0.95
• Comparable to the KIDS data

3
Contaminant correction

• Galfit does ?²-minimization at all costs
• Galfit needs to know that there is a second
  object (or third, or) to fit it with a new
  component
• Need to think of selection criteria for primary
  AND secondary objects
• One possibility (the one I made my tests with)
• Object inside fitting region, near primary object
  and not more than a few magnitudes fainter
• Object just outside fitting region but brighter
  than primary
• ? add component

4
Contaminant correction
Run 1a Run 1b Run 2a Run 2b
DETECT_MINAREA (min. area for 2nd object) 30 50 50 70
MINAREA_PRIMARY 100 100 150 150
Number of objects 35.000 25.000 25.000 20.000
Objects fitted 11367 11453 7239 7278
Needed time 90 h 75 h 80 h 74 h
5
Running Galfit with different profiles
DETECT_MINAREA (for 2nd object)
30 MINAREA_PRIMARY 100 35000 objects in
catalogue 11800 objects as primary objects
Profile Expdisk Sersic B/D (SersicExpdisk)
total time / time per obj. (2.6GhZ P4 4GB Ram) 39.5 h 12 s 47 h 14.4 s 102 h 32 s
6
Galfit got stuck
7
Galfit got stuck

• Need a maximum number of iterations
• If this already exists
• ? Check why it didnt stop