Kinematics and neutral hydrogen properties of the giant low surface brightness galaxy UGC 2936

We present high-sensitivity, high-velocity resolution VLA H I observations of the giant low surface brightness (LSB) galaxy, UGC 2936. Like the giant LSBs presented in Pickering et al., UGC 2936 is a large and massive galaxy. Its H I mass is nearly 10¹⁰ M_⊙ h^-2₇₅, it has detectable H I extending beyond 30 kpc h^-1₇₅, and it is a fast rotator (V_max ≃ 250 km s^-1) with a slowly rising rotation curve. This galaxy also exhibits warping in the outermost isophotes of the optical images that appears to be visible in the H I distribution and kinematics as well. This galaxy's high inclination and relatively large amount of Hα emission provides a unique opportunity to compare high-quality H I and optical rotation curves in the same LSB galaxy. The optical and H I data show good agreement as long as the effects of beam smearing on the H I rotation curve are taken into account. A large part of the disk of UGC 2936 lies above the critical density for star formation as described by Kennicutt. This is consistent with the relatively large amount of star formation occurring within the disk of this galaxy and perhaps brings into question whether this galaxy should be considered a true LSB galaxy.