Supernovae Origin for the Low-latitude Intermediate-velocity Arch and the North Celestial Pole Loop

Abstract

Supernova explosions attributed to the unseen companion in several binary systems identified by the Third Gaia Data Release (Gaia DR3) may be responsible for a number of well-known and well-studied features in the radio sky, including the low-latitude intermediate-velocity (LLIV) arch and the north celestial pole (NCP) loop. Slices from the longitude–latitude–velocity data cube of the λ-21 cm Galactic neutral hydrogen HI4PI survey show multiple signatures of an expanding shell. The source of this expansion, which includes the LLIV arch on the approaching side, may be the neutron star candidate in the Gaia DR3 1093757200530267520 binary. If we make the simplifying assumptions that the expansion of the cavity is uniform and spherically symmetric, then the explosion took place about 700,000 yr ago. The momentum is in reasonable agreement with recent model estimates for a supernova this old. The H i on the receding side of this cavity is interacting with the gas approaching us on the near side of a second cavity. The NCP loop appears to be located at the intersection of these two expanding features. The neutron star candidate in the Gaia DR3 1144019690966028928 binary may be (in part) responsible for this cavity. Explosions from other candidates may account for the observed elongation along the line of sight of this second cavity. We can use the primary star in these binaries to anchor the distances to the LLIV arch and NCP loop, which are ∼167 and ∼220 pc, respectively.