How to use galfit (and galphot)

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How to use galfit (and galphot)

• Gijs Verdoes Kleijn

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Galfit ( Galphot)

• Galfit 2-D galaxy profile fitting routines (C)
• Author Chien Peng (STScI)
• Awe-status basics incorporated
• Reference
• zwicky.as.arizona.edu/cyp/work/galfit/galfit.html
  
• Peng etal 2002 AJ 124, 266
• Galphot ellipse fitting routine (fortran)
• Author Marijn Franx (Leiden)
• To be incorporated
• ref www.strw.leidenuniv.nl/franx
• Franx etal 1989 AJ 98, 538

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What galfit does

• fitting 2-D parameterized axisymmetric functions
  to images
• Any (in)dependent combination of
  Sersic(devauc/expo),nuker,gaussian,king,moffat,sky
  
• Disky/boxy shapes
• Error weighing
• Inclusion PSF via FFT
• Meant for well resolved galaxies explore
  sub-structure
• Future plans of galfit more profiles, more
  isophotal shapes, allow for axial twists, spiral
  structure.
• No batch mode perl scripts exist (used for GEMS
  survey)

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Astro-WISE implementation

• Python wrapper
• Give input to galfit c-code from python
• Inputoutputlinks to SourceList contained in
  classes instances of which are stored in database
• no alteration c-code
• Written by Ewout Helmich, help from C.
  Trachternach GVK
• Description
• Input SLID, SID, cut-out via cut-out server,
  configuration parameters
• Defaults for configuration parameters based on
  SourceList
• Initial guess x position SourceList x position
• Size cut-out image 15 SourceList r_eff

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Examples of usage (see how-to)
Run galfit using local cpu
awegtfrom DBRecipes.GalFit import GalFitTask
awegttask GalFitTask(instrument'WFI',
slid57424, sids31,52,73, models'sersic',
'sky', commit1) awegttask.execute()
Run galfit using parallel cluster
awegtfrom astro.net.dpu import Processor awegt
from astro.local.Environment import Env awegtdpu
Processor(Env'dpu_name') awegtdpu.run('GalFit',
i'WFI', slid57424, sids31,52,,73,
m'sersic', 'sky', commit1)
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Examples continued
Show model parameters for SLID57424,
SID31,52,73 for last run
awegt mysources (57424, 31), (57424, 52),
(57424, 73) awegtmodels awegtfor slid, sid
in mysources awegt q (GalFitModel.SLID
slid) (GalFitModel.SID sid) awegt model
q.max('GFID') awegt models.append(model)
awegtfor m in models awegt m.show_model_paramet
ers()
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Now Future

• Code itself can be found at
• opipe/astro/main/GalFitModel.py (show it)
• opipe/DBRecipes/GalFit.py (Task)
• Current implementation
• Sersicsky on ReducedScienceFrame,RegriddedFrame
• Contaminant fitting included
• Next steps
• All profiles (Sersicsky implemented rest coming
  soon
• Psf convolution
• Background subtraction statistics right
• Constraints file inclusion

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Summary

• Surface photometry tools getting ready in
  Astro-WISE for large data sets
• GalFit implemented basics, more coming soon
• Easy (re-)processing and inspecting of galfit
  results on large number of galaxies
• GalPhot is coming..