The Astro-Wise standard stars (with a focus on OmegaCAM)

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The Astro-Wise standard stars (with a focus on
OmegaCAM)

• Gijs Verdoes Kleijn Ronald Vermeij
• For the Astro-Wise consortium

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Aim sampling complete FOV with photometric
calibrators
OmegaCAM FOV
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Aim sampling complete FOV with photometric
calibrators
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Aim sampling complete FOV with photometric
calibrators

• Accurate photometric calibration ( per chip)
• Quantifying sky concentration effects

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Photometric accuracies

• Instrumental requirement 5 accuracy in
  photometry with usual data reduction
• Our estimate with Astro-Wise infrastructure 2-3
  achievable with bit extra work on top usual data
  reduction

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OmegaCAM calibration plan
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All-year round monitoring field near South
Equatorial Pole
Purpose monitor instrument performance and
atmospheric conditions through night
Candidate field (ra,dec)(51.429,89.04)deg
(l,b)(302.29 -27.82)deg
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Standard star catalog in Astro-Wise

• 8 equatorial fields
• Final catalog will be produced from OmegaCAM
  observations of fields in first year.
• Currently a preliminary version in place
• to be used during commissioning.
• derived from WFC/INT La Palma data
• WFC data was calibrated using Landolt standards
  (transformed to Sloan system)

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The standard star fields
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The content of a field
Field SA92
? Landolt stars published data (transformed to
ugriz) Sloan published data ? AW2S, our
secondary standards obtained from WFC/INT La
Palma data
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Deriving a Zeropoint

• Reduce standard starfield
• Associate stars with entries in
• standard star catalog.
• Sigma clip to discard outliers
• Estimate zeropoint for each remaining star
• Zeropoint weighted mean of estimates

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Work in progress

• Good determination random and systematic errors
  of standard star
• magnitude in the catalog
• measured flux
• Propagation of these errors to ZPT

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Aw2S-SDSS3 magnitude residuals
SA92
SA101
SA104
SA107
SA113
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SA92
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SA101
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SA104
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SA107
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SA113
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Independent photometry checks

• Galaxy number counts

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Stellar locus in color-color space
Izevic et al 2004
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In conclusion

• First version of standard star catalog in
  Astro-Wise in place accuracy/systematics
  analysis in progress.
• Additional independent photometry checks being
  considered.