Structure-dynamics relations for late-type spiral and dwarf irregular
  galaxies revisited
  Scaling relations among structural and kinematical features of 79 late-type
spiral and dwarf irregular galaxies of the SPARC sample are revisited or newly
established. The mean central surface brightness <$\mu_{0,[3.6]}$> = 19.63
$\pm$ 0.11 mag arcsec$^{-2}$ allows for a clear-cut distinction between low and
high surface brightness galaxies irrespective of luminosity. The geometry of
rotation curves is characterized by the relation $dv(R_d)/dr \approx
v_{max}/R_{max}$. For the rotation curve decompositions we apply dark matter
halos of Burkert and of pseudo-isothermal type. The disk mass-to-light ratios
exhibit an asymmetric bimodal distribution with the dominant peak located at
0.2. The baryonic mass fraction at intermediate radii is included to address
both an adjusted baryonic Tully-Fisher relation and the significance of
deviations from the mean radial acceleration relation. The mean radial decrease
of the baryonic mass fraction within galaxies is quantified. The Burkert halo
parameters obey $\rho_0 \propto r_0^{-1.5}$ with considerable scatter, but
allowing for $v_{max}$ as a third variable we find $\rho_0 \propto
r_0^{-1.84}v_{max}^{2.00}$ with small scatter. The halo central surface density
$\rho_0r_0$ strongly correlates with the observed radial acceleration at
different galactocentric radii. We introduce an alternative universal rotation
curve that is based on the non-singular total matter density profile
$\rho_{total}(r) \propto (v_{max}^2/r^2)[1-(1-r/r_c)\exp(-r/r_c)]^2$, with the
scaling parameter $r_c$ correlating with the halo core size $r_0$ and with
$R_{max}$. Fitting the synthetic URC to a selection of galaxies, the co-added
doubly-normalized rotation curves exhibit a high degree of similarity.
