Properties of Molecular Gas in Galaxies in Early and Mid Stage of the Interaction: I. Distribution of Molecular Gas

TL;DR

This study maps molecular gas in early and mid-stage interacting galaxies, revealing that molecular gas distribution differs from atomic gas and stars, with less central concentration indicating initial redistribution due to interaction.

Contribution

First detailed CO mapping of interacting galaxies in early and mid stages, showing molecular gas distribution changes during initial galaxy interactions.

Findings

Molecular gas mass exceeds 10^9 solar masses in studied galaxies.

Molecular gas distribution is off-center and less concentrated than in isolated galaxies.

Differences in molecular gas distribution are attributed to galaxy interactions.

Abstract

We present the results of 12CO(J = 1-0) mapping observations toward four interacting galaxies in early and mid stages of the interaction to understand the behavior of molecular gas in galaxy-galaxy interaction. The observations were carried out using the 45-m telescope at Nobeyama Radio Observatory (NRO). We compared our CO total flux to those previously obtained with single-dish observations and found that there are no discrepancy between them. Applying a typical CO-H2 conversion factor, all constituent galaxies have molecular gas mass more than 10^9 M_sun. Comparisons to HI, Ks and tracers of SF such as Halpha, FUV, 8 um and 24 um revealed that the distribution of molecular gas in interacting galaxies in the early stage of the interaction differs from atomic gas, stars and star-forming regions. These differences are not explained without the result of the interaction. Central concentration of molecular gas of interacting galaxies in the early stage of the interaction is lower than that of isolated galaxies, which suggests molecular gas is distributed off-centre and/or extends in the beginning of the interaction.