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Optical photometry

Optical photometry. Coverage. CFH12K BVRI (limited area; but all patches have full filter coverage) Less stable calibration, but contiguous area Megacam ugriz (9h lacks u; 21h lacks i) Wide field, stable reduction: chip gaps. 2h coverage. B/u V/g R/r I/i/K/IRAC. 9h coverage. B/u V/g

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Optical photometry

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  1. Optical photometry

  2. Coverage • CFH12K • BVRI (limited area; but all patches have full filter coverage) • Less stable calibration, but contiguous area • Megacam • ugriz (9h lacks u; 21h lacks i) • Wide field, stable reduction: chip gaps

  3. 2h coverage B/u V/g R/r I/i/K/IRAC

  4. 9h coverage B/u V/g R/r I/i/K/IRAC

  5. 14h coverage B/u V/g R/r I/i/K/IRAC

  6. 21h coverage B/u V/g R/r I/i/K/IRAC

  7. Combining systems • R and r: Put both on SDSS system • Small additional correction • Good to within 0.05 mag • I and i • Fit small correction as function of (B-V) • Good to 0.05 mag • K (SOFI), K (INGRID) • Little overlap. Only good to ~0.2 mags. • Spitzer 3.6 to K • Fit [3.6]-k vs z. Then k-correct. • Probably good to 0.2 mags

  8. K-corrections • Blanton v4.1.4. Computed at z=0, 0.3 and 0.4. • Extinction correct; add some error (0.02 to 0.05) to mags • Checked on SDSS data Observed (g-r) Colour-coded according to rest-frame colour

  9. Results

  10. Blue points: activity based on [OII] or IR • Red points: IR-passive

  11. Groups Field

  12. Red fraction Groups Field • If either (g-r) or (B-V) are red

  13. Dusty red galaxies

  14. Old fraction Groups Field Old Fraction

  15. Things to do • Comparison with • Poggianti clusters • z=0 groups (e.g. Weinmann) • Font et al. models • Take a closer look at individual groups. • Faint blue galaxies: anything unusual??

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