SIMBAD references

We present Very Large Array Hi observations of the gas-rich, interacting spiral galaxies, NGC1253/1253A (Arp 279). The larger of the two galaxies, NGC1253, has a very pronounced Hi ring and well-defined spiral structure. The velocity structure of the Hi data shows a sudden change at the position of the spiral arms; we identify this change as evidence of a strong spiral shock and hence proceed to estimate the pattern speed, Ω_p, of the spiral arms in NGC1253. Assuming that the pattern speed is constant across the disc our derived value places the outer Lindblad resonance (OLR) at the position of the observed Hi ring. As an accumulation of gas is expected at the OLR when this falls within the disc of a galaxy this agreement provides independent support for the derived value of Ω_p.