H I observations of giant low surface brightness galaxies

Abstract

We have used the Nançay Radio Telescope to obtain new global H I data for 16 giant low surface brightness (LSB) galaxies. Our targets have optical luminosities and disk scale lengths at the high end for spiral galaxies (LB ∼ 1010 L⊙ and hr ≳ 6 kpc for H0 = 75 km s-1 Mpc-1), but they have diffuse stellar disks, with mean disk surface brightnesses ≳ 1 magnitude fainter than normal giant spirals. Thirteen of the galaxies previously had been detected in H I by other workers, but the published H I observations were either confused, resolved by the telescope beam, of low signal-to-noise, or showed significant discrepancies between different authors. For the other 3 galaxies, no H I data were previously available. Several of the galaxies were resolved by the Nançay 3′.6 E-W beam, so global parameters were derived from multiple-point mapping observations. Typical H I masses for our sample are ≳ 1010 M⊙, with MHI/LB = 0.3 - 1.7 (in solar units). All of the observed galaxies have published optical surface photometry, and we have compiled key optical measurements for these objects from the literature. We frequently find significant variations among physical parameters of giant LSB galaxies reported by various workers.