IRAC Instrument Handbook - IRSA - California Institute of Technology

List of Figures 190
IRAC Instrument Handbook
FIGURE 4.2: IRAC INSTRUMENT SUPER SKYFLATS SHOWING THE FLATFIELD RESPONSE
AS MEASURED ONBOARD, FOR CHANNELS 1–4................................................................34
FIGURE 4.3. ARRAY LOCATION-DEPENDENT PHOTOMETRIC CORRECTION IMAGES. CH 1
IS IN THE UPPER LEFT, CH 2 IN THE UPPER RIGHT, CH 3 IN THE LOWER LEFT AND
CHANNEL 4 IN THE LOWER RIGHT. ....................................................................................44
FIGURE 4.4: DEPENDENCE OF POINT SOURCE PHOTOMETRY ON THE DISTANCE OF THE
CENTROID OF A POINT SOURCE FROM THE NEAREST PIXEL CENTER IN CHANNEL 1.
THE RATIO ON THE VERTICAL AXIS IS THE MEASURED FLUX DENSITY TO THE MEAN
VALUE FOR THE STAR, AND THE QUANTITY ON THE HORIZONTAL AXIS IS THE
FRACTIONAL DISTANCE OF THE CENTROID FROM THE NEAREST PIXEL CENTER. .....46
FIGURE 4.5. THE IN-FLIGHT IRAC POINT RESPONSE FUNCTIONS (PRFS) AT 3.6, 4.5, 5.8 AND
8 MICRONS. THE PRFS WERE RECONSTRUCTED ONTO A GRID OF 0.3” PIXELS, ¼ THE
SIZE OF THE IRAC PIXEL, USING THE DRIZZLE ALGORITHM. WE DISPLAY THE PRF
WITH BOTH A SQUARE ROOT AND LOGARITHMIC SCALING, TO EMPHASIZE THE
STRUCTURE IN THE CORE AND WINGS OF THE PRF, RESPECTIVELY. WE ALSO SHOW
THE PRF AS IT APPEARS AT THE IRAC PIXEL SCALE OF 1.2”. THE RECONSTRUCTED
IMAGES CLEARLY SHOW THE FIRST AND SECOND AIRY RINGS, WITH THE FIRST
AIRY RING BLENDING WITH THE CORE IN THE 3.6 AND 4.5 µM DATA...........................47
FIGURE 4.6. THE IRAC POINT RESPONSE FUNCTIONS (PRFS) AT 3.6, 4.5, 5.8 AND 8.0
MICRONS. THE PRFS WERE GENERATED FROM MODELS REFINED WITH IN-FLIGHT
CALIBRATION TEST DATA INVOLVING A BRIGHT CALIBRATION STAR OBSERVED AT
SEVERAL EPOCHS. CENTRAL PRFS FOR EACH CHANNEL ARE SHOWN ABOVE WITH A
LOGARITHMIC SCALING TO HELP DISPLAY THE ENTIRE DYNAMIC RANGE. THE PRFS
ARE SHOWN AS THEY APPEAR WITH 1/5TH THE NATIVE IRAC PIXEL SAMPLING OF 1.2
ARCSECONDS TO HIGHLIGHT THE CORE STRUCTURE. ...................................................49
FIGURE 4.7. EXTENDED SOURCE FLUX CORRECTION FACTORS; SOLID LINES REPRESENT
EXPONENTIAL FUNCTION FITS TO THE DATA. ALSO INDICATED ARE CORRECTION
FACTORS DERIVED FROM ZODIACAL LIGHT TESTS, AND GALACTIC HII REGION
TESTS (E.G. MARTIN COHEN'S GLIMPSE VS. MSX, PRIVATE COMMUNICATION)..........58
FIGURE 4.8. EXTENDED SOURCE FLUX CORRECTION FACTORS FOR GALAXIES (SOLID
LINES) VERSUS THE PSF APERTURE CORRECTION FACTORS (DOTTED LINES). THE
MAIN DIFFERENCE BETWEEN THE TWO IS THE TRULY DIFFUSE SCATTERING
INTERNAL TO THE ARRAY...................................................................................................58
FIGURE 4.9. NOISE VERSUS BINNING LENGTH IN CHANNEL 1. TO MAKE THIS PLOT THE
SURFACE BRIGHTNESS WAS MEASURED IN NINE REGIONS ACROSS AN OBJECT-
MASKED MOSAIC. THESE REGIONS ARE NOT NEAR THE BRIGHT GALAXIES, STARS,
OR DIFFUSE PLUMES. THE NOISE IS DEFINED AS THE STANDARD DEVIATION OF
THOSE NINE REGIONS. THE BOX SIZE IS INCREMENTALLY INCREASED UNTIL THE
BOX LENGTH IS MANY HUNDREDS OF PIXELS. FOR REFERENCE THE SOLID LINE
SHOWS THE EXPECTED LINEAR RELATION. .....................................................................61
FIGURE 4.10. NOISE VERSUS BINNING LENGTH IN CHANNEL 2. TO MAKE THIS PLOT THE
SURFACE BRIGHTNESS WAS MEASURED IN SIX REGIONS ACROSS AN OBJECT-
MASKED MOSAIC. THESE REGIONS ARE NOT NEAR THE BRIGHT GALAXIES, STARS,
OR DIFFUSE PLUMES. THE NOISE IS DEFINED AS THE STANDARD DEVIATION OF