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“Signals from the Noise in the FIRST Survey” Dr. Richard White Space Telescope Science Institute |
| Empty fields in astronomical sky surveys are not truly empty. Image stacking of "blank" fields can recover the properties of source populations with fluxes a factor of 100 or more below the survey detection threshold. We are exploring the radio sky into the nanoJansky regime by employing image stacking using the FIRST survey. Mean estimates of radio flux density, luminosity, etc., are derivable for any source class having arcsecond positional accuracy. We have used this technique to compute the mean radio properties for 41,295 quasars from the SDSS DR3 catalog. There is a tight correlation between optical and radio luminosity, with interesting deviations that depend on the quasar optical color and spectral type. I will also discuss surprising new results regarding the radio emission from star-forming and quiescent galaxies from the SDSS. Image stacking is a superb tool for understanding the radio emission from AGN and star formation. |