Early Science with the Large Millimeter Telescope: discovery of the 12CO(1-0) emission line in the ring galaxy, VIIZw466

TL;DR

This study reports the first detection of CO(1-0) emission in the collisional ring galaxy VII Zw466, revealing insights into its molecular gas content, star formation, and potential CO-dark gas presence, challenging previous assumptions about its gas deficiency.

Contribution

First detection of CO(1-0) emission in VII Zw466, providing new insights into its molecular gas properties and star formation behavior in collisional ring galaxies.

Findings

VII Zw466 may be HI-dominated or contain CO-dark molecular gas.

The galaxy's star formation law aligns with standard models despite H2 deficiency.

Feedback processes may deplete molecular gas or hide it from CO observations.

Abstract

We report an early science discovery of the CO(1-0) emission line in the collisional ring galaxy, VII Zw466, using the Redshift Search Receiver instrument on the Large Millimeter Telescope Alfonso Serrano.The apparent molecular-to-atomic gas ratio either places the ISM of VII Zw466 in the HI-dominated regime or implies a large quantity of CO-dark molecular gas, given its high star formation rate. The molecular gas densities and star formation rate densities of VII Zw466 are consistent with the standard Kennicutt-Schmidt star formation law even though we find this galaxy to be H2-deficient. The choice of CO-to-H2 conversion factors cannot explain the apparent H2 deficiency in its entirety. Hence, we find that the collisional ring galaxy, VII Zw466, is either largely deficient in both H2 and HI or contains a large mass of CO-dark gas. A low molecular gas fraction could be due to the enhancement of feedback processes from previous episodes of star formation as a result of the star-forming ISM being confined to the ring. We conclude that collisional ring galaxy formation is an extreme form of galaxy interaction that triggers a strong galactic-wide burst of star formation that may provide immediate negative feedback towards subsequent episodes of star formation---resulting in a short-lived star formation history or, at least, the appearance of a molecular gas deficit.