The Omega CAM photometric systems Omega CAM calibration

The Omega. CAM photometric systems

Omega. CAM calibration plan (1) Basic Omega. CAM terminology : ● ● ● Key bands vs User bands Key band -> User band transformation tables Monolithic filters and calibration filter Polar field and equatorial fields Monitoring

Omega. CAM calibration plan (2)

Omega. CAM calibration plan (3) Important considerations : Omega. CAM is continuously maintained in the Key bands ( u', g', r', i' ) ● standard fields only observed in User bands if the science programme of the night warrants it ● photometric calibration is done per-chip ●

Omega. CAM photometric standard stars Standard fields used for daily calibration : ● ● field centered on south celestial pole (polar field) eight equatorial fields : SA 92, SA 95, SA 98, SA 101, SA 104, SA 107, SA 110, SA 113 Available photometric bands : u', g', r', i'

Omega. CAM photometric standard stars : preparatory programs Establishing photometric standards : INT Secondary Standards Preparatory Programme ● Omega. CAM Secondary Standards Programme Photometric standards presently available : ● classisal Landolt catalog ● stars from Sloan Digital Sky Survey ● new : candidate Sloan standards for SA 98 ●

Omega. CAM photometric standard stars : INT/La Palma preparatory program (1) Establishing photometric standards for SA 98 : data was processed with the Astro-Wise system ● photometric transformation coefficients determined using Sloan standards ● no illumination correction was required for INT ● Results : ~ 23. 000 candidate secondary standards covering a Fo. V of 1. 1 deg X 1. 1 deg

Omega. CAM photometric standard stars : INT/La Palma preparatory program (2) Monitoring the quality of the night Standard extinction coefficients adopted : u' = 0. 47 g' = 0. 19 r' = 0. 09 i' = 0. 05

Omega. CAM photometric standard stars : INT/La Palma preparatory program (3) Color terms : u' : none detected g' : 0. 14 +/- 0. 01 r' : none detected i' : 0. 07 +/- 0. 01

Omega. CAM photometric standard stars : INT/La Palma preparatory program (3) Zeropoints : u' : 23. 725 +/- 0. 019 (1) 23. 772 +/- 0. 019 (2) 23. 575 +/- 0. 039 (3) 23. 542 +/- 0. 029 (4) g' : 24. 939 +/- 0. 016 (1) 25. 064 +/- 0. 005 (2) 25. 091 +/- 0. 008 (3) 25. 122 +/- 0. 004 (4) r' : 24. 579 +/- 0. 015 (1) 24. 702 +/- 0. 010 (2) 24. 806 +/- 0. 009 (3) 24. 803 +/- 0. 010 (4) i' : 24. 126 +/- 0. 018 (1) 24. 255 +/- 0. 012 (2) 24. 412 +/- 0. 011 (3) 24. 413 +/- 0. 007 (4)

Omega. CAM photometric standard stars : INT/La Palma preparatory program (5) Comparing the photometric solution with an independent field

Omega. CAM photometric pipeline (1) : top-level recipes Top-level recipes of the photometric pipeline : Phot. Cal. Extract. Resulttable --> deriving catalogs ● Phot. Cal. Extract. Zeropoint --> deriving zeropoints ● Phot. Cal. Monitoring --> monitoring ● Illumination. Correction. Verify ● Illumination. Correction ●

Omega. CAM photometric pipeline (2) : photometric catalog Photometric pipeline works with catalogs Making these catalogs is always the first processing step in the photometric pipeline photcat = Phot. Src. Catalog() photcat. astrom_params = astrom photcat. frame = frame photcat. refcat = refcat photcat. make() photcat. inspect()

Omega. CAM photometric pipeline (3) : extinction + zeropoint Last processing step in photometric pipeline Extinction derived earlier in one of many ways End result used in image pipeline photom = Photometric. Parameters() photom. extinct = extinct photom. photcat = photcat photom. make() photom. inspect()

Omega. CAM photometric pipeline (4) : illumination correction Verification of the presence of sky concentration effects Plot shows the variation of the zeropoint as a function of its position on the detector block plot = create_plot('Illum. Verify') plot. show(photcats) Verification of a WFI image observed in filter #844

Omega. CAM photometric pipeline (5) : illumination correction Characterising the sky concentration effect illum = Illumination. Correction() illum. photcats = photcats illum. make() illum. inspect()

Omega. CAM photometric pipeline (6) : illumination correction Peak to peak variation : 0. 94 – 1. 03 f = Illumination. Correction. Frame() f. illum = illum f. chip = chip f. make() image = Image('MEF. fits') image. frames = frames image. make() The eight illumination correction frames for WFI filter #844

Omega. CAM photometric systems : resources “Omega. CAM Data Flow System – users and programmers manual V 2. 11” ● “Omega. CAM Secondary Standards preparatory programme – progress report” ● http: //portal. astro-wise. org/ ●