The objects identified as "stars or artifacts."
-
by
mlpeck
There were 7 of them. I checked them all in DR9 Navigate, and 6 are clearly galaxies that happen to be close to, and in some cases nearly swamped by the glare from, bright stars. I don't see obvious signs that the spectra are contaminated however.
The seventh is kind of interesting because it actually looks like a star, and I think it's been discussed here: AGS00001uo. From looking at the spectrum though I think it was correctly identified as a z=0.326 galaxy by the SDSS pipeline, which actually makes it a pretty interesting object.
Posted
-
by
JeanTate
in response to mlpeck's comment.
Cool! 😃
AGS00001uo is more likely an extended source, not a point source.
How to tell?
If you click on PhotoObj in the left-hand panel of the DR9 Explore page, you get a very long list of parameters, with values. These are derived, automatically, by the photometric pipeline (though some are imports). Down near the bottom are five parameters, called "probPSF_X", where X is (u, g, r, i, z). In the DR9 Browser Schema, under PhotoObjAll, these are defined as "Probablity object is a star in each filter"1. For AGS00001uo, three are 1 (g, r, and z), and two 0 (u and i) ... a somewhat mixed result, especially as the object is red (so there little u-band flux), but it's quite bright in the i-band, and in that it's an extended source.
1 By "star" it means "point source", because it's the photometric pipeline, and has no idea what the redshift is!
Posted