An investigation of Sloan Digital Sky Survey imaging data and multiband scaling relations of spiral galaxies

ABSTRACT We have compiled a sample of 3041 spiral galaxies with multiband gri imaging from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7; Abazajian et al. 2009) and available galaxy rotational velocities, V, derived from H i linewidths. 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 ∼8 and ∼30 per cent with our parameters compared to similar relations built with SDSS parameters. The tightest VRL relations are obtained with the i‐band radius, R23.5, i, measured at 23.5 mag arcsec−2, and the luminosity L23.5, i, measured within R23.5, i. Our VRL scaling relations compare well, both in scatter and slope, with similar studies (though such comparisons depend sensitively on the nature and size of the compared samples). The typical slopes, b, and observed scatters, σ, of the i‐band VL, RL and RV relations are bVL = 0.27 ± 0.01, bRL = 0.41 ± 0.01, bRV = 1.52 ± 0.07, and σVL = 0.074, σRL = 0.071, σRV = 0.154, respectively. Similar results for the SDSS g and r bands are also provided. Smaller scatters may be achieved with more pruned samples. We also compute scaling relations in terms of the baryonic mass (stars + gas), Mbar, ranging from Mbar ≃ 108.7 to 1011.6 M⊙. Our baryonic velocity–mass (VM) relation has slope 0.29 ± 0.01 and a measured scatter σmeas = 0.076 dex.