Is the aperture that fed the SDSS spectrograph fibers 3" in diameter, or 3" in radius?
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JeanTate
The SDSS spectrograph which was used to produce the DR7 spectra, not that used for BOSS (etc), because it's data derived from the DR7 spectra which we're working with in this project, right?
Why is this important?
Because I think we'll have to throw out all the objects whose spectra sample considerably less than the light from all the stars (and gas) in the galaxy targeted. Details of how we make such decisions ('cuts' I think they're called, in astronomer-speak) will depend crucially on how much of a galaxy's light ended up entering the spectrograph fiber, and the size of the aperture is perhaps the biggest factor in that.
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jtmendel
scientist, moderator
The fibers are 3" in diameter.
You're absolutely correct that the fraction of total galaxy light observed by the SDSS fibers -- sometimes called the fiber covering fraction -- can have a significant effect on the observed spectrum. This is actually one thing that control galaxies can be very helpful for. Because there is a relatively good correlation between galaxy stellar mass and physical (as opposed to angular) size, comparing to galaxies at fixed stellar mass and redshift often does a reasonable job of controlling for variations in covering fraction. It might be interesting to see if something like this is feasible for the QS and QC samples.
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