High Resolution H I Distributions and Multi-Wavelength Analyses of Magellanic Spirals NGC 4618 and NGC 4625

TL;DR

This study provides high-resolution H I observations of Magellanic spiral galaxies NGC 4618 and NGC 4625, revealing differences in their gas dynamics, star formation activity, and interaction status, with implications for understanding galaxy evolution.

Contribution

It offers detailed multi-wavelength analysis of two Magellanic spirals, highlighting their distinct gas properties and star formation patterns, and clarifies their non-interacting status despite morphological similarities.

Findings

NGC 4625 has a quiescent, uniform H I disk with no H I holes.

NGC 4618 shows dynamic interplay between star formation and H I distribution.

The galaxies are kinematically distinct, indicating no interaction.

Abstract

We present a detailed analysis of high resolution H I observations of the Magellanic spiral galaxies NGC 4618 and NGC 4625. While the H I disk of NGC 4625 is remarkably quiescent with a nearly uniform velocity dispersion and no evidence of H I holes, there is a dynamic interplay between star formation and the distribution of neutral hydrogen in NGC 4618. We calculate the critical density for widespread star formation in each galaxy and find that star formation proceeds even where the surface density of the atomic gas is well below the critical density necessary for global star formation. There are strong spatial correlations in NGC 4618 between UV emission, 1.4 GHz radio continuum emission, and peaks in the H I column density. Despite the apparent overlap of the outer disks of the two galaxies, we find that they are kinematically distinct, indicating that NGC 4618 and NGC 4625 are not interacting. The structure of NGC 4618 and, in particular, the nature of its outer ring, are highly suggestive of an interaction, but the timing and nature of such an interaction remain unclear.