6-arm blue grand design of NGC 309

TL;DR

This paper investigates the spiral structure of galaxy NGC 309, proposing a two-pattern model with six blue arms formed through gas dynamics, contributing to understanding grand design spirals.

Contribution

It introduces a novel schematic of a six-arm blue spiral in NGC 309, explaining its formation via gas-dynamics and dual-pattern symmetry.

Findings

Two-pattern spiral structure with six blue arms proposed

Gas-dynamics may induce blue spiral formation

Red and blue patterns form a grand design with two-fold symmetry

Abstract

The geometry and physics of the spiral structure of the giant Hubble type Sc galaxy NGC 309 is studied. A schematic of two patterns with three arms in each is suggested for the blue spiral. The red and blue patterns form together a grand design with two-fold symmetry. A possible gas-dynamics explanation of the phenomenon is suggested which shows how the two-arm red spiral may induce the formation of the six-arm coherent blue spiral. Key words: galaxies: individual (NGC 309) -- galaxies: spiral