Meta-analysis from different tracers of the small Local Arm around the
  Sun - extent, shape, pitch, origin
  The Sun in not located in a major spiral arm, and sits in a small Local Arm
(variously called arm, armlet, blob, branch, bridge, feather, finger, segment,
spur, sub-arm, swath, etc). The diversity of names for the Local Arm near the
Sun indicates an uncertainty about its shape or pitch or its extent from the
Sun in each galactic quadrant, as well as an uncertainty about its origin. Here
we extract data about the small Local Arm near the Sun, from the recent
observational literature, over many arm tracers, and we use statistics in order
to find the its mean extent from the Sun, its possible shape and pitch angle
from the direction of galactic longitude 90 degrees. Employing all tracers, the
Local Arm is about 4 kpc long by 2 kpc large. The Sun is within 1 kpc of the
center of the local arm.
  Proposed bridges and fingers are assessed. These bridges to nearby spiral
arms and fingers across spiral arms may not reach the nearest spiral arms,
owing to kinematic and photometric distance effects. We then compare these
statistical results with some predictions from recent models proposed to
explain the local arm (perturbations, resonances, density wave, halo
supercloud, debris trail from a dwarf galaxy).
  The least controversial models involve importing materials from elsewhere
(halo supercloud, debris trail) as a first step, and to be later deformed in a
second step (by the Galactic differential rotation into become roughly parallel
to spiral arms) and then subjected to ongoing forces (global density waves,
local perturbations).
