A Catalog of Galactic Atomic Hydrogen Position-Position-Velocity Filaments

TL;DR

This paper provides a comprehensive catalog of 3D Galactic HI filaments, analyzing their properties and distribution, revealing insights into their structure, origins, and relation to turbulence in the interstellar medium.

Contribution

The paper introduces a new catalog of 3D HI filaments using an advanced algorithm, expanding the understanding of their properties and spatial distribution in the Galaxy.

Findings

Identified 3333 HI filaments across the sky.

Filament widths are consistently ~12 arcminutes, constrained by resolution.

Hierarchical structure suggests turbulence influences filament formation.

Abstract

We present a catalog of 3D Galactic HI filaments over 1/3 of the sky using Galactic Arecibo L-band Feed Array HI (GALFA-HI) data. The 3D filaments are defined to be linear HI features that are continuous in position-position-velocity (PPV) and are found with fil3d, an algorithm that expands on the 2D FilFinder. The catalog contains 3333 HI filaments between +/- 50 km/s at a range of Galactic positions. 1542 of the PPV filaments are identified as local at the distance of the wall of the Local Bubble, and 209 are likely at the disk-halo interface of our Galaxy. The catalog and properties of the PPV filaments are obtained after an unsharp mask (USM) is applied to the data. The widths of the filaments are consistently ~12' (0.34 pc at 100 pc), and constrained by the 4' resolution. The local filaments have median properties of N_HI = $6 \times 10^{18}$ cm$^{-2}$, M_HI = 0.17 M_sun, FWHM = 3.2 km/s, and length of 6.4 pc. The disk-halo population has similar column densities, but the median FWHM = 7.7 km/s, consistent with them being higher z-height, warmer structures. The L $\propto$ M$^{0.5}$ relationship found for the HI filaments and their bundling on the sky are consistent with a hierarchical structure, and is likely related to turbulence playing a role in their formation.