# Spiral Galaxy Mass Models:

## MOND Models

The following is the abstract for a paper in production entitled `MOND
Mass Models of Spiral Galaxies'.

Using two-dimensional velocity maps and I-band photometry, we have
created modified Newtonian dynamics (MOND) mass models of 40 spiral
galaxies, complementing previous work. The mass-to-light ratio
parameters of the models are presented along with a discussion of the
correlation between these values and the galaxies' colors. We also
demonstrate this correlation for a subsample of Hydra cluster
galaxies. Using a Bayesian comparison technique, we derive
quantitative relations between MOND, Newtonian stars-only, and several
different dark matter halo models to determine which type of model is
most successful in describing the data. While we have not explored an
exhaustive set of models, we believe they represent a fair cross
section of likely possibilities. We also note that common systematic
uncertainties typical of these galaxies can render such statistical
comparisons inappropriate. We further discuss the details of two
galaxies which provide preliminary evidence against MOND and
investigate the impact of relaxing the assumption of constant
mass-to-light ratios in these cases. We conclude that; 1) in a
"chi-by-eye" sense, MOND mass models can fit spiral galaxy velocity
maps as well as dark matter halo models, 2) unlike dark matter halo
models of these galaxies, MOND models produce a trend between
mass-to-light ratios and galaxy color, 3) in a strict statistical
sense, fixed-distance, spatially constant mass-to-light ratio MOND
mass models generally do not describe spiral galaxy velocity fields as
economically as do some dark matter halo models, 4) one must be very
careful when interpreting such a statement, as systematic effects in
distance estimates, gas content, and mass-to-light gradients can
strongly impact MOND fits.

The PDF draft version of this paper is available
here