Very wide galaxy pairs of the northern and southern sky

Abstract

We present highly accurate observations of the 21 cm line of hydrogen in galaxies made at the Arecibo and Parkes Observatories. The galaxies observed have been identified, through rigorous selection criteria applied to the CfA and SSRS catalogs, as being members of pairs with projected separations of up to 1.5 Mpc (H₀ = 75 km s⁻¹ Mpc⁻¹). These observations form the completion of the Chengalur-Nordgren galaxy pair sample with data previously published by Chengalur, Nordgren and colleagues. The new selection criteria used in this paper are an extension to larger projected separations of the criteria used previously. Forty-nine new galaxies are observed, while H I is detected in 41 of them. With the addition of these galaxies, the completed sample has highly accurate H I velocities for a total of 219 galaxies.