Dark and luminous matter in bright spiral galaxies
I present photometrically calibrated images and surface photometry in the BVRJH and K-bands of 26, and in the g, r, and K-bands of 5 nearby bright (B<12.5 mag) spiral galaxies with inclinations between 30-65 degrees spanning the Hubble Sequence from Sa to Scd. Data are from The Ohio State University Bright Spiral Galaxy Survey, the Two Micron All Sky Survey, and the Sloan Digital Sky Survey Second Data Release. Radial surface brightness profiles are extracted, and integrated magnitudes are measured from the profiles. Axis ratios, position angles, and scale lengths are measured from the near-infrared. A 1-dimensional bulge/disk decomposition is performed on galaxies with a non-negligable bulge component. Radial stellar mass distributions are estimated by applying color-M/L relations derived from spectrophotometric spiral galaxy evolution models to the photometry. When available, radial gas masses are added to the radial stellar mass distributions to produce radial baryonic mass distributions. For each galaxy, a rotation curve due to its radial baryonic mass distribution is calculated, taking into account both the bulge and disk components when necessary. All of the galaxies have high-quality rotation curves available in the literature which allows us to calculate radial dark matter distributions for each galaxy by comparison with the baryonic mass rotation curves. Most galaxies are found to have maximal stellar disks, but seven are found to be submaximal in their inner parts (inner five scale radii). The following quantities are derived to characterize the radial baryonic and dark matter content of galaxies, and are found to correlate with Hubble Type: the peak velocity of the baryonic rotation curve (V*max), the radius at which the dark matter contributes 10% to the observed rotation curve (R10), and the radius at which dark matter contributes 50%(RX). From the radial distribution of beta(r), I find that although the behavior of the dark matter distributions are qualitatively similar from galaxy to galaxy, there is systematic scatter among them to argue against a universal rotation curve. The general qualitative shape the beta(r) curves is what is expected from an exponential baryonic disk and a rotation curve that is nearly flat at large radii.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:galaxies rotation curves dark matter photometry
Date of Publication:01/01/2004