Summary of MD08.refstack.20130401

(back to MediumDeepFields summary)

Similar to the MD08.GR0 (MD.GR0) refstacks for the 2011/2012 season, these include recent improvement and input cuts to help constrain the convolved stacks as well. Because the refstack is made with reprocessed pixels, the refstack pixels will now have the ubercalibration and all current detrend calibrations for the new season. Overall fewer inputs to the refstack were done this round and may not be as deep as last season.

MD08 observations:

• starting ~mid-April 2013, already pre-obs in March
• end-April 2012 through early Sept. 2012
• early February 2011 through early Oct. 2011
• early April 2010 through end Sept. 2010
• mid-April 2009 through end Sept. 2009

Filter	N total	N FWHM<8 pixels	N (FWHM<8 pixels for 2012
g	531	454	53
r	547	469	43
i	547	536	64
z	651	605	109
y	684	561	94

• 2012 wasn't a great season for MD08

Status:

• 04/0/13 selected exposure reprocessing chip->warp for refstack started (late due to power outage and messy system crashes)
• 04/05 reftests finished, full refstack started
• 04/06 refstack finished, checked and problem skycells found/fixed
• 04/07 staticsky single filter only finished
• (04/09) mappings finished, reftest+refstack to distribution, refstack setup, recently missed exposures setup for diffims..

MD08.V3 Processing (chip->warp + refstack)

Exposure reprocessing was done for only a limited number (~150) of the best images from 2010-2012 to provide a balance of N input warps versus best seeing, excluding exposures with large background, low zeropoints and large elongation.

Processing chip-warp and the refstack itself has the same label, data_group

• label: MD08.refstack.20130401 --> once set as active refstack for diffims, stack label will change to MD08.refstack, chip/cam/warp label will remain the same
• data_group: MD08.refstack.20130401

Newer ipp-20130307 tag used.

Histograms of the FWHM major and minor and elongation from camera stage value (full exposure) for the sample of reprocessed exposures (red) and used for refstack.20130401 (top blue) and used for refstack.20120422 (bottom blue) in grizy order

Test stack (reftest) sample also made again for skycell.055 with different number of input warps.

• label: MD08.reftest.20130401
• data_group:
  • MD08.reftest.20130401.c#f<FWHM cut> where #=comparison run, <FWHM cut>=cut <fwhm_major from camProcessedExp x10>
  • MD08.reftest.20130401.all.<FWHM cut> where all means 03/2010+2011+2012 data possible, <FWHM cut>=cut <fwhm_major from camProcessedExp x10>
  • MD08.reftest.20130401.2012.<FWHM cut> where 2012 means 2012 data only for season stack example case, <FWHM cut>=cut <fwhm_major from camProcessedExp x10>
• the main field center shift was through ~May 2010, but is a very small shift. Excluding 2009 since usually not very good, or uncharacteristically too good (avoiding problems basically)
• c1 cuts

  filter: (FWHM set), elongation, zeropoint, background upper limits
  y: (3.5, 3.8, 4.0, 4.2), 1.3, 22.8, 4000 -- 
  z: (3.8, 3.9, 4.0, 4.2), 1.3, 24.0, 3000 -- 
  i: (4.0, 4.2, 4.4, 4.6), 1.25, 24.3, 2000 --
  r: (4.0, 4.3, 4.5, 4.7), 1.25, 24.3, 500 -- 
  g: (4.8, 5.0, 5.1, 5.3), 1.25, 24.3, 300 -- 
  

Summary comparison table with the approximate FWHM (major) as the PSF FWHM from a center field skycell (V3=055) after running psphot on the stacks.

| data_group                    | filter  | stack_id | warps_in | warps_rej |  FWHM_MAJ   IQ_FW1 (pixels)
+-------------------------------+---------+----------+----------+-----------+
--> 2012/2013 refstack

--> reftest comparisons				

--> previous 2011/2012 refstack				

As before, the FWHM_MAJOR with the central skycell can be variable and more so with largely different input sets. Comparison with the psf_major/minor maps are more useful between refstack versions.

Problems

(need to update)

• generally edge skycells have issues, need better containment of those still. (see core coverage below). g,r has additionally ratty edge skycells.
• like others, greater % of inputs rejected (20-30%) so per pixel input is less, but still of order 30 inputs per pixel
• some convolved stacks have poorer FWHM PSF but not significant enough to be likely improved by reprocessing using DEEP_STACK config as in earlier MD fields (ie s083r, and a bit s011i, s017g)
• as this is a field with a large center offset, the center is more contained in skycell.044 and has the degraded FWHM in gri
• skycell details:
  • y: s032,042,052,062,063,083 cell print through problem (from ota14, cell 31); s034 bright junk; s044 center/dither spot; s003,004,040 cell odd/bright chunks on edge
  • z: s005,006,040 undersampled, messy edge; s034,062 bright junk
  • i: s006,040 undersampled, messy edge; s015,034,062 (057 less) bright junk
  • r: s005,038 undersampled, messy edge; s003,031,032,033,037,045,051,053, and more ghosts; s014,034,074 (057 less) bright junk; s021,022 strong scattered light
  • g: s045 poor cell print through and ghosts; s013,034,037,047,054,057(less),064,073,074(bad),s084 bright junk; ; s003,004,017,038,050,068,071,077 undersampled, messy edge; s051,055 strong, s024,042,066,067,072 smeared, 021, ghosts; s021,022 scattered light;

Core coverage -- one of the larger shifted pointings so very different from normal distribution of skycells (also see detection efficiency maps below)

082-087
071-078
061-068
051-058
041-048
031-038
021-028
012-017

• skycells with fewer inputs: 012,017,021,028,071,078,082; 012,021,071,078,082 ~50% or less

Refstack Summary

Refstacks run through the staticsky (single filter mode so basic psphot with deteff measurements) and skycal stage on the unconvolved stacks to make the map plots (full 5 filter version still having occasional faults to work through):

• label: MD08.refstack.20130401, MD08.refstack.20130401
• data_group: MD08.refstack.20130401.1x20130407, MD08.refstack.20130401.1x20130407.cal20130407

Source photometry psf_major,_minor maps (grizy):

Magnitude of sources@5-sigma maps (grizy):

Detection efficiency magnitude @50% recovery (500 fakes, grizy):