Optical photometry
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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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Coverage
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
2h coverage

B/u

V/g

R/r

I/i/K/IRAC


9h coverage
9h coverage

B/u

V/g

R/r

I/i/K/IRAC


14h coverage
14h coverage

B/u

V/g

R/r

I/i/K/IRAC


21h coverage
21h coverage

B/u

V/g

R/r

I/i/K/IRAC


Combining systems
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


K corrections
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




Groups

Field


Red fraction
Red fraction

Groups

Field

  • If either (g-r) or (B-V) are red



Old fraction
Old fraction

Groups

Field

Old Fraction


Things to do
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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