VizieR Online Data Catalog: Quantifying maximum discs in galaxies (Starkman+, 2018)

A galaxy can be broadly decomposed into a few baryonic components: gas disc, stellar disc, and bulge (if present). The conversion from 21cm flux to atomic gas mass is specified by the physics of the spin-flip transition, fixing the gas contribution. The conversion from stellar light to stellar mass is less well determined. For bulge and stellar disc, we need to introduce mass-to-light ratios, denoted as Y_bul and Y_disc, respectively. The values of Y_bul and Y_disc can be fixed using stellar population synthesis models (Bell & de Jong 2001ApJ...550..212B; McGaugh & Schombert 2014AJ....148...77M; Schombert & McGaugh 2014PASA...31...36S; Lelli et al. 2016AJ....152..157L, 2016ApJ...827L..19L), but in this work we will use them as free parameters to determine their maximum allowed values from a dynamical perspective.

We develop a fitting scheme that matches the baryonic rotation curve to the observed one at small radii, specifically near the 'turning radius' where the rotation curves start to approach a flat part. The algorithm produces good results in disc-dominated cases. However, for galaxies with bulges, the mass-to-light ratios of bulge and disc can be degenerated. In these cases, we break the degeneracy by imposing Y_bul>Y_disc. This choice is motivated by stellar population synthesis models. To confirm the algorithm's efficacy and estimate the uncertainties, a Markov Chain Monte Carlo (MCMC) routine was also run on all galaxies, giving consistent results.

(2 data files).