Blue galaxy in front? or lensed from behind.

• by Budgieye moderator

  DECaLS dr2 Browser cutout

  http://legacysurvey.org/viewer/jpeg-cutout/?ra=150.5450&dec=5.7023&zoom=16&layer=decals-dr2

  SDSS dr9 z=0.084 Er 0.00002

  http://skyservice.pha.jhu.edu/DR9/ImgCutout/getjpeg.aspx?ra=150.54562328&dec=5.702303&scale=0.2&width=200&height=200&opt=G

  Interesting that the colour difference doesn't show in SDSS, since different wavelengths are used.

  SDSS dr9 photoz 0.090652
  zErr 0.041737

  http://skyservice.pha.jhu.edu/DR9/ImgCutout/getjpeg.aspx?ra=150.54421441&dec=5.70217184&scale=0.2&width=200&height=200&opt=G

  http://skyserver.sdss.org/dr9/en/tools/explore/obj.asp?id=1237658423012819123

  The trouble with photoz is that it has such large error. The blue galaxy could be in front 0.05, beside it 0.09. or behind it 0.13 . A value of 0.13 isn't far enough away be a lens.

  Photoz can be wrong, but this looks OK. The blue colour couldn't be due to lensing of a distant galaxy, since that is not enough distance behind it. The colour of lensed galaxies is a brighter blue , from all the UV light. This is white-blue, the colour of star forming galaxies.

  Funny bright yellow area on both sides of the nucleus.

  Posted July 5, 2016 6:29 AM