Cross-correlation of 2MASS galaxy sample with SDSS

I cross-correlated my 2MASS extended sources list(7 < K20 < 11.5) with Chris Kochanek’s list and got 3712 galaxies which is 88.5% of Kochanek sample. Then I cross-correlated this with SDSS photometric catalog in NYUVAC. And 64% of them(2390) has SDSS photometric counter parts.

However If I select galaxies with addtion of another selection criterior, which excludes galaxies close to the edge of 2MASS scan(I found the distance from the edge of scan in 2MASS XSC and calculated 3*r_k20fe, then selected galaxies whose 3*r_k20fe < edge distance), the fraction of excluded galaxies by this criterior increases as I go to brighter galaxies( more than 50% in K20<9). This means that my sample is systematically biased to more compact galaxies since large bright galaxies are more frequently excluded by this distance criterior.

This bias can’t be avoided eventhough I used smaller factor instead of 3. The factor ensuring to have enough sky and small exclusion fraction is required to get homogeneous and uniform sample.


~ by ilsangyoon on July 16, 2008.

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