GMRT H I study of giant low surface brightness galaxies

Abstract

We present H I observations of four giant low surface brightness (GLSB) galaxies UGC 1378, UGC 1922, UGC 4422 and UM 163 using the Giant Meterwave Radio Telescope. We include H I results on UGC 2936, UGC 6614 and Malin 2 from literature. H I is detected from all the galaxies and the extent is roughly twice the optical size; in UM 163, H I is detected along a broken disc encircling the optical galaxy. We combine our results with those in literature to further understand these systems. The main results are the following: (1) the peak H I surface densities in GLSB galaxies are several times 1021 cm−2. The H I mass is between 0.3 and 4 × 1010 M⊙; dynamical mass ranges from a few times 1011 M⊙ to a few times 1012 M⊙. (2) The rotation curves of GLSB galaxies are flat to the outermost measured point with rotation velocities of the seven GLSB galaxies being between 225 and 432 km s−1. (3) Recent star formation traced by near-ultraviolet emission in five GLSB galaxies in our sample appears to be located in rings around the galaxy centre. We suggest that this could be due to a stochastic burst of star formation at one location in the galaxy being propagated along a ring over a rotation period. (4) The H I is correlated with recent star formation in five of the seven GLSB galaxies.