APEX Maps Reveal Extended Molecular Gas in Nearby Galaxies, Up 5 kpc

The outer reaches of galaxies hold vital clues to their evolution, revealing the impact of mergers, tidal forces, and internal structures like bars and spiral arms, but observing these faint signals requires sensitive telescopes capable of mapping large areas of the sky. Akhil Lasrado, Claudia Cicone, and Axel Weiss, from the University of Oslo and the Max-Planck-Institut für Radioastronomie, have used the Atacama Pathfinder Experiment (APEX) to map the extended molecular gas in two nearby galaxies, the Circinus galaxy and NGC 1097. Their observations reveal molecular gas extending further than previously known, up to 5 kiloparsecs in the Circinus galaxy and beyond in NGC 1097, and demonstrate the presence of distinct structures, including a bar-like feature in the Circinus galaxy and tidal gas streams in NGC 1097 resulting from its interaction with a companion galaxy. These findings highlight the power of single-dish telescopes like APEX, and pave the way for future large-scale molecular gas studies with the next generation of instruments, such as the Atacama Large Aperture Submillimeter Telescope.

The interstellar medium frequently experiences significant events during a galaxy’s lifetime, including interactions with other galaxies and the influence of large-scale structures. Studying the distribution of molecular gas, the raw material for star formation, provides crucial insights into these processes, and is best achieved by mapping large areas of the sky with sensitive telescopes. 6 kiloparsecs from the galaxy’s centre. NGC 1097: * Maximum Distance: Molecular gas was detected extending up to 4. 2 kiloparsecs from the galaxy’s centre. A kiloparsec is a unit of distance used in astronomy, equivalent to approximately 3,260 light-years. These distances represent the extent of the observed molecular gas, likely tracing the outer regions of the galactic disk or material pulled away during gravitational interactions.

Extended Molecular Gas Reaches Galactic Outskirts

Recent observations with the APEX telescope have revealed extended structures of molecular gas in Circinus and NGC 1097, challenging previous understandings of galactic evolution. Researchers successfully mapped the distribution of molecular gas across both galaxies, detecting gas at unprecedented distances, up to 6 kiloparsecs in Circinus and 18 kiloparsecs in NGC 1097. These findings demonstrate that molecular gas extends much further from galactic centres than previously known, highlighting the importance of studying gas in galactic outskirts. The total mass of molecular gas detected in Circinus was approximately 2.

1 billion times the mass of our Sun, while NGC 1097 contained around 4. 7 billion solar masses of molecular gas. Notably, the APEX observations revealed a distinct bar-like structure of molecular gas within Circinus, aligning with the galaxy’s central bar and demonstrating a direct link between large-scale galactic features and the distribution of star-forming material. In NGC 1097, the team identified tidal structures of molecular gas, indicating ongoing interaction with its companion galaxy, NGC 1097A. This suggests that gravitational interactions can significantly redistribute molecular gas, potentially triggering star formation. These observations underscore the importance of studying molecular gas in galactic outskirts to fully understand the processes driving galaxy evolution.

Extended Molecular Gas Maps of Nearby Galaxies

This research presents new, large-scale maps of molecular gas in Circinus and NGC 1097, achieved using the APEX telescope, revealing gas extending further than previously observed in both systems. The team detected molecular gas up to 6 kiloparsecs from the centre of Circinus and 18 kiloparsecs from NGC 1097, allowing for a more complete picture of the gas distribution within these galaxies. Molecular gas masses were calculated as 2. 1 billion solar masses for Circinus and 4. 7 billion solar masses for NGC 1097, consistent with earlier measurements.

Notably, the observations confirm the presence of a molecular bar structure in Circinus and reveal a significant molecular gas component within the tidal tail of NGC 1097, likely stripped from the galaxy during its interaction with NGC 1097A. Analysis of the gas kinematics in Circinus shows a longer rotation period at larger distances, consistent with the presence of a bar, while the tidal feature in NGC 1097 exhibits a velocity gradient and coincides with dust emission, suggesting ongoing interaction. Future observations with more powerful telescopes, such as AtLAST, will be needed to further investigate these complex gas flows.