2018/08/18 by Parodi, Bernhard R.
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.1808.06140
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 = 19.63 ± 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(Rd)/dr ≈ vmax/Rmax. 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 ρ0 ∝ r0-1.5 with considerable scatter, but allowing for vmax as a third variable we find ρ0 ∝ r0-1.84vmax2.00 with small scatter. The halo central surface density ρ0r0 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 ρtotal(r) ∝ (vmax2/r2)[1-(1-r/rc)exp(-r/rc)]2, with the scaling parameter rc correlating with the halo core size r0 and with Rmax. Fitting the synthetic URC to a selection of galaxies, the co-added doubly-normalized rotation curves exhibit a high degree of similarity.