The HSB/LSB Galaxies NGC 2403 and UGC 128

Abstract

We have decomposed the rotation curves of the high surface brightness (HSB) galaxy NGC2403 and the low surface brightness (LSB) system UGC128. Both galaxies have a similar baryon content and rotational velocities but have very different disk scale lengths and angular momentum contents. On a linear scale, the rotation curve of the HSB galaxy rises much steeper than that of the LSB galaxy but once scaled with the scale lengths of the stellar disks, the rotation curves are practically indistinguishable. The inferred stellar M/Ls from maximum-disk decompositions are reasonable for the HSB galaxy but are excessively high for the LSB galaxy. Assuming both galaxies are embedded in a similar halo results in more acceptable stellar M/Ls for both galaxies with the HSB galaxy being close to a maximum-disk situation while the LSB galaxy is dark matter dominated.