PGC55

  • RA: 0.15583
  • Dec: 33.60094
  • Ra = 0.67 (arcmin)
  • Rb = 0.20 (arcmin)
  • PA = 13.12 (degrees)

# position angle (PA) [Degrees: Up=0, Left=90]"

run_sex <root> <ra> <dec>
./run_sex.csh pgc55_g 0.15583 33.60094

SExtractor first outputs

filter Mag X0 Y0 RA DEC Re Ra Rb b/a PA
mag pix pix deg deg arcmin arcmin arcmin deg
pgc55_u 16.99 458.3 459.6 0.1555 33.6014 0.17 0.75 0.20 0.27 9.30
pgc55_g 16.11 457.8 459.1 0.1555 33.6013 0.15 0.67 0.20 0.30 13.12
pgc55_r 15.75 457.8 458.3 0.1555 33.6013 0.14 0.65 0.20 0.31 13.20
pgc55_i 15.53 457.8 457.8 0.1555 33.6012 0.14 0.65 0.20 0.31 13.53
pgc55_z 15.38 458.0 457.8 0.1555 33.6012 0.15 0.50 0.14 0.28 12.21

GLGA-qa

minskywid = 27. / as_pix	 ; 27 arcsec is minimum sky width
factor = 1.5                     ;  1.5 default
skyinner = factor*semimajor
skyouter = semimajor*sqrt(1+factor^2) > (skyinner+minskywid)  


Sigma multiplier for thresshold (default =  2.5): 2.0
Magnitude faint limit (default =  24.0): 25

I increased the aperture size, until the difference between APR and ASY magnitudes are less than 0.05 mag.

SKY

  • u
    final sky/px, skyerr/px     [mJy/px]:    0.00068215   0.00010009  ds/s = ~15%
    final musky, muskyerr  [AB mag/as^2]:     22.304     0.159
    
  • g
    final sky/px, skyerr/px     [mJy/px]:    0.00083100   0.00003426  ds/s = ~4%
    final musky, muskyerr  [AB mag/as^2]:     22.090     0.045
    
  • r
    final sky/px, skyerr/px     [mJy/px]:    0.00194121   0.00005404  ds/s = ~3%
    final musky, muskyerr  [AB mag/as^2]:     21.168     0.030
    
  • i
    final sky/px, skyerr/px     [mJy/px]:    0.00371400   0.00009490  ds/s = ~3%
    final musky, muskyerr  [AB mag/as^2]:     20.464     0.028
    
  • z
    final sky/px, skyerr/px     [mJy/px]:    0.01061923   0.00031765  ds/s = ~3%
    final musky, muskyerr  [AB mag/as^2]:     19.323     0.032
    


Changing the sky aperture

Now, I keep everything the same but the size of the inner aperture

minskywid = 27. / as_pix	 ; 27 arcsec is minimum sky width
factor = 2.0                     ;  1.5 default
skyinner = factor*semimajor
skyouter = semimajor*sqrt(1+factor^2) > (skyinner+minskywid)  

SKY

  • u
    final sky/px, skyerr/px     [mJy/px]:    0.00068317   0.00010508  ds/s = ~15%
    final musky, muskyerr  [AB mag/as^2]:     22.302     0.167
    
  • g
    final sky/px, skyerr/px     [mJy/px]:    0.00083044   0.00003543  ds/s = ~4%
    final musky, muskyerr  [AB mag/as^2]:     22.090     0.046
    
  • r
    final sky/px, skyerr/px     [mJy/px]:    0.00193863   0.00005487  ds/s = ~3%
    final musky, muskyerr  [AB mag/as^2]:     21.170     0.031
    
  • i
    final sky/px, skyerr/px     [mJy/px]:    0.00371275   0.00009834  ds/s = ~3%
    final musky, muskyerr  [AB mag/as^2]:     20.464     0.029
    
  • z
    final sky/px, skyerr/px     [mJy/px]:    0.01062065   0.00033289  ds/s = ~3%
    final musky, muskyerr  [AB mag/as^2]:     19.323     0.034
    

  • left-top : factor = 2.0 i.e. expand by 100%
  • right-bottom: factor = 1.5 i.e. expand by 50% (original)


Knowing the fact that estimated error for the background level is <~5%:

  • left-top: Adding 1% to the estimated sky value
    IDL code: sdss_radprof.pro
    skyint = 1.01*skyint     ; ehsan-edit
    
  • right-bottom: original

Left panel shows that, the sensitivity to the sky background is too high and probably the estimated precession for the sky background level is wrong.

Final conclusion up to this point (for pgc55): If the profile looks good, we can claim that we've got to the precession of 5% in magnitude (e.g. 0.05 mag). Slightly changing the position angle (7 degrees) and axial ratio does not change 0.05 mag precession.


GLGA Mask


Archangel:

sky = 0.000827037089005
skysig = 2.71460323481e-06

pgc55_profile1.png

rm pgc55_g.clean pgc55_g.xml xml_archangel -c pgc55_g archangel xml_archangel -e pgc55_g sky 0.00083100 xml_archangel -e pgc55_g skysig 0.00003426

Last modified 5 years ago Last modified on Apr 28, 2016, 12:50:40 AM

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