15 December 2008Science from UKIDSS II WFCAM Science Pipeline Update WFCAM Science Pipeline Update Jim Lewis, Mike Irwin & Marco Riello Cambridge Astronomy Survey Unit

15 December 2008Science from UKIDSS II WFCAM processing summary Semesters05A05B06A06B07A07B08A08BNights ► an average of 70% of telescope time ► 115 TB Raw Data (30 TB compressed) ► 200 TB processed Data (50 TB compressed) ► 4 million 2k x 2k images

15 December 2008Science from UKIDSS II Processing steps reminder ► Internet raw data transfer -> Cambridge ► Ingest and verify, record OMP MSB status -> tape backup ► Dark and reset anomaly correction <- master darks ► Flat field correction <- master twilight flats ► Decurtaining - remove variable pattern noise ► Detector crosstalk removal - channels within quadrants ► Sky background estimation and subtraction -> sky images ► Interleaving 1x1, 2x2 or 3x3 ► Dither/jitter stacking -> science product image ► Catalogue generation ► Astrometric and photometric calibration ► Quality control checks

15 December 2008Science from UKIDSS II Why Do Background Correction ? typical before and after background correction #1

15 December 2008Science from UKIDSS II Update since 07B  extra processing to remove parquet floor pattern  monthly photometric recalibration (Hodgkin et al. 2008)  MSBTid logs available immediately after stage I processing  nebulosity filtering post-processing option  new observing and reduction strategies for improved background subtraction for large extended objects  bug fixes/workarounds including a long-standing one

15 December 2008Science from UKIDSS II problems with detectors #2,3 K-band sky #3 stacked final image

15 December 2008Science from UKIDSS II Parquet floor processing LAS Y-band detector #2

15 December 2008Science from UKIDSS II Sky flipping/offsets ► extended objects observed on a given detector ► objects are then ‘flipped’ to a different detector ► background for ‘object’ detector in one jitter determined from compliment observation jitter ► objects of interest are observed at all times (advantage over offset sky strategy) ► offset skies only for large objects, e.g. M101, clusters, which cover more than 1 detector

15 December 2008Science from UKIDSS II Bugs:  indexing bug in catalogue Petrosian routine  only affects deblended objects and is now fixed  fundamental problem with circular apertures  workaround found that can be applied retrospectively  all catalogues will be repaired at end of 08B processing deblended objects Petrosian fluxes and radii

Photometry in regions of high nebulosity - M17 K-band WFCAM