Wednesday, November 25, 2009

Likely Testing

I'm trying to track down why the likelihood method is missing quasars that other targeting methods are finding.

The plot of human-confirmed QSOs that were in the target list for the likelihood method. The magenta are targeted by likelihood, the cyan are missed by likelihood, the white are targeted only by likelihood (click on image to enlarge):

Color-Color (u-g vs g-r)
of likelihood selected objects (magenta),
likelihood missed objects (cyan),
likelihood only objects (white)

The reason this plot looks different than yesterdays is because I was accidentally plotting both QSOs and stars on the plot yesterday. The above human-confirmed QSOs.

Below is a log-log plot of the likelihood selection variables L_everything vs L_qso for the likelihood-selected QSOs (magenta), the likelihood-missed QSOs (cyan), the likelihood-selected stars (red), and the likelihood-missed stars (green) you can see the value of L_ratio we cut on is the slope of the dividing line between these populations (click on image to enlarge):

L_everything vs L_qso

I've looked at the individual fluxes of the likelihood selected/missed QSOs to see if there an obvious place in flux-color space where we can get more of the missing objects. They are all intermixed.

David Schlegel suggested increasing the 'added errors' in the likelihood calculation to see if this improves things. I am re-running the likelihoods on these ~1400 objects (above) with larger errors. The hope is that because we are have such a sparse sample of the QSOs, that by increasing the errors we'll allow for objects that are "farther away" in flux-space to be selected. The errors are currently on the order of ~1%. I am re-running with 10%, however David suggests that I do it with 5%, so I'll run with that too.

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