The corotation gap in the Galactic HI distribution

TL;DR

This paper identifies and characterizes a ring-shaped HI density gap near the solar circle in the Milky Way, aligning with theoretical predictions of gas flow at the corotation resonance.

Contribution

It provides observational evidence of the corotation gap in Galactic HI distribution, confirming theoretical and simulation-based expectations.

Findings

Average gap radius of 8.3 kpc from the Galactic center

Gap width of approximately 0.8 kpc

Characteristics match predictions of gas flow near corotation resonance

Abstract

We used the HI data from the LAB survey to map the ring-shaped gap in HI density which lies slightly outside the solar circle. Adopting $R_0$= 7.5 kpc, we find and average radius of 8.3 kpc and an average gap width of 0.8 kpc. The characteristics of the HI gap correspond closely to the expected ones, as predicted by theory and by numerical simulations of the gas flow near the corotation resonance.