Giant molecular clouds in M 33: are they susceptible to dynamical friction?

TL;DR

This study investigates whether dynamical friction affects the orbits of giant molecular clouds in galaxy M 33, finding it may influence clouds in the central 2 kpc but implies longer cloud lifetimes than typically accepted.

Contribution

It introduces a semi-analytical model to assess the impact of dynamical friction on GMCs in M 33, highlighting potential orbital changes in the galaxy's inner region.

Findings

Dynamical friction can alter GMC orbits within 2 kpc of M 33.

GMC lifetimes would need to be >10^8 years for significant orbital changes.

The effect is limited to the galaxy's central region.

Abstract

Most of giant molecular clouds (GMCs) in M 33 are connected with spiral-like gaseous arms (filaments) with the exception of the inner 2 kpc region where the link between the arms and GMCs disappears (see Tosaki et al. 2011). We check whether it may be caused by the dynamic friction retarding the clouds. Using semi-analytical model for this galaxy we calculate the dynamics of GMCs of different masses situated at different initial galactocentric distances in the disk plane. We demonstrate that the dynamical friction may really change the orbits of GMCs in the central 2 kpc-size region. However in this case the typical lifetimes of GMCs should be close to or greater than $10^8$~yr, which is larger than the usually accepted values.