We have compiled a sample of 3041 spiral galaxies with multi-band gri imaging from the Sloan Digital Sky Survey ( SDSS ) Data Release 7 and available galaxy rotational velocities , V , derived from H I line widths .
We compare the data products provided through the SDSS imaging pipeline with our own photometry of the SDSS images , and use the velocities , V , as an independent metric to determine ideal galaxy sizes ( R ) and luminosities ( L ) .
Our radial and luminosity parameters improve upon the SDSS DR7 Petrosian radii and luminosities through the use of isophotal fits to the galaxy images .
This improvement is gauged via VL and RV relations whose respective scatters are reduced by \sim 8 % and \sim 30 % compared to similar relations built with SDSS parameters .
The tightest VRL relations are obtained with the i -band radius , R _ { 23.5 ,i } , measured at 23.5 mag ~ { } arcsec ^ { -2 } , and the luminosity L _ { 23.5 ,i } , measured within R _ { 23.5 ,i } .
Our VRL scaling relations compare well , both in scatter and slope , with similar studies ( such comparisons however depend sensitively on the nature and size of the compared samples ) .
The typical slopes , b , and observed scatters , \sigma , of the i -band VL , RL and RV relations are b _ { VL } = 0.27 \pm 0.01 , b _ { RL } = 0.41 \pm 0.01 , b _ { RV } = 1.52 \pm 0.07 , and \sigma _ { VL } = 0.074 , \sigma _ { RL } = 0.071 , \sigma _ { RV } = 0.154 .
Similar results for the SDSS g and r bands are also provided .
Smaller scatters may be achieved for more pruned samples .
We also compute scaling relations in terms of the baryonic mass ( stars + gas ) , M _ { bar } , ranging from M _ { bar } \simeq 10 ^ { 8.7 } M _ { \odot } to 10 ^ { 11.6 } M _ { \odot } .
Our baryonic velocity-mass ( VM ) relation has slope 0.29 \pm 0.01 and a measured scatter \sigma _ { meas } = 0.076 dex .
While the observed VL and VM relations have comparable scatter , the stellar and baryonic VM relations may be intrinsically tighter , and thus potentially more fundamental , than other VL relations of spiral galaxies .