Sample Galaxies

  • I had a look at 3 following cases. I have done photometry with and without sky subtraction. It seems that the sky has been already subtracted and turning off the sky subtraction does not change the results that much. Therefore, I think that we can ignore the sky subtraction part for now.
  • Another issue that I notices is that the outer region of the galaxies, and across the entire field (the whole image) the sky average level is negative. I don't know what that means for now, however its a problem where the growth curve drops down at a certain point.

No image "calibrator_ps_don_g" attached to PS-photometry-test01


http://www.ifa.hawaii.edu/~ehsan/test/PS_pgc5284_panstarrs_images.jpg

  • This is the case that Pan_STARRS and SDSS are completely consistent. Even though the center of the galaxy is saturated in the PS image, it still gives a reasonable result.
  • On the left plot, it is clear that around 1.5 arcmin, the average surface brightness becomes negative, that's why there is no point on the plot, and on the right side, the same plot, the residual sky subtracted brightness might be meaningless. That's the reason sky brightness errors are huge/unreasonableness.
  • (Left/Top?: without sky subtraction - Right/Bottom?: with sky subtarction)


http://www.ifa.hawaii.edu/~ehsan/test/PS_pgc40516_panstarrs_images.jpg

  • This case appears fainter in all PS images.
  • On the left plot, it is clear that around 2 arcmin, the average surface brightness becomes negative, that's why there is no point on the plot.
  • (Left/Top?: without sky subtraction - Right/Bottom?: with sky subtarction)


http://www.ifa.hawaii.edu/~ehsan/test/PS_pgc93031_panstarrs_images.jpg

  • This case appears brighter in g-band PS image.
  • In this case not subtracting the sky does not help. Push the point towards brighter magnitudes.
  • (Left/Top?: without sky subtraction - Right/Bottom?: with sky subtarction)


Last modified 4 years ago Last modified on Nov 23, 2016, 3:47:31 PM

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