Date Sent: Tuesday, June 06, 2006 10:45 AM From: neill@uvic.ca Subject: RE: SDSS 'dr5' color terms and zeropoints Here are the results from the latest D2 and D3 catalogs, provided by Mark. These are from our culled tertiary standards (i.e. our psf standards) and are compared against the pre-release sdss 'dr5' catalogs from the D2 and D3 regions that we got from David Schlegel. As we suspected, the slope differences in g' do not go away. There was some movement in the slopes, but nothing major. Mark gave me zeropointed magnitudes, so the plots now have their y-axis ranges near zero and the slopes will appear inverted compared with previous plots I have sent. I'll send these results to David Schlegel later today. If you have any comments, please let me know. -Don
Subject: RE: SDSS 'dr5' color terms and zeropoints Date: Mon, 29 May 2006 14:58:58 -0700 From: Don NeillOK, here is an update, mostly minor. I've included error estimates on the slopes provided by a linear least-squares fit of the binned data. The bins are indicated by the red filled circles (color-cut) and the green (full set). The error bars are the rms scatter in the bin. If I use the error in the mean of the bin, then I no longer get probable linear fits, even though the errors go way down. I've also included a plot of the coverage, since we were curious. The circles are definitely big enough, but there are gaps in D2. In comparing the D2 and D3 slopes, you can see a batch of blue outliers in the D3 points that are forcing slightly steeper slopes than D2, which does not show those outliers. A conservative approach would be to say that the error on the slopes is the difference between the D2 and D3 values. A bolder approach is to say that the D2 values are probably more correct. Check out the plots and see what you think. The numbers and plots are attached. Enjoy, -Don