Evolution of the spiral structure of galaxies from the HST COSMOS field

TL;DR

This study examines the evolution of spiral arm pitch angles in galaxies from the HST COSMOS field, revealing similarities with nearby galaxies and a tendency for pitch angles to decrease from redshift 1 to 0, supporting tidal or instability origins.

Contribution

It provides the first detailed analysis of spiral arm pitch angles across a significant redshift range, linking their evolution to galaxy formation theories.

Findings

Pitch angles in distant galaxies are similar to those in nearby galaxies.

Within a galaxy, the scatter of pitch angles is about half the mean.

Pitch angles tend to decrease from redshift 1 to 0.

Abstract

We have investigated the pitch angle ($\psi$) of the spiral arms of galaxies in the Hubble Space Telescope COSMOS field. The sample consists of 102 face-on galaxies with a two-armed pattern at a mean redshift $\langle z \rangle \approx 0.5$. The typical values of $\psi$ in the spiral arms of distant galaxies are shown to be close to those for nearby spiral galaxies. Within one galaxy the scatter of $\psi$ for different arms is, on average, half the mean pitch angle. In the $z$ range from 1 to 0 we have found a tendency for $\psi$ to decrease. Our analysis of the $\psi$ distributions in galaxies at different redshifts is consistent with the assumption that in most of the galaxies at $z \leq 0.5$ the spiral arms are tidal in origin or they arose from transient recurrent instabilities in their disks.