Hsi-An Pan, Lihwai Lin, Sara L. Ellison, Mallory D. Thorp, Sebastián F. Sánchez, Asa F. L. Bluck, Francesco Belfiore, Joanna M. Piotrowska, Jillian M. Scudder, and William M. Baker, The Astrophysical Journal , Volume 964, Issue 2, id.120, 22 pp. April (2024)
Article Title : The ALMaQUEST Survey. XIII. Understanding Radial Trends in Star Formation Quenching via the Relative Roles of Gas Availability and Star Formation Efficiency
Full Article:https://ui.adsabs.harvard.edu/abs/2024ApJ…964..120P/abstract
Galaxies can be broadly categorized into two main types: star-forming galaxies and quiescent galaxies. Studying the formation and relationship between these two types is crucial for understanding galaxy evolution. Stars (like our Sun) form within cold, dense molecular clouds in galaxies. When a star-forming galaxy stops converting gas into new stars, a phenomenon known as “star formation quenching” occurs. This indicates that the galaxy’s evolution has reached a late stage and it will gradually evolve into a quiescent galaxy. Therefore, this process is essential for understanding why some galaxies transition into a “red and dead” state. Studying “star formation quenching” helps us understand the life cycle of galaxies and their role in shaping the structure of the universe.
From the perspective of gas, there are two mechanisms that cause star formation quenching: Mechanism 1: “Reduced gas content”: The gas content within the galaxy decreases, causing a rapid decrease in the star formation rate. And Mechanism 2: “Low star formation efficiency”: The gas content within the galaxy does not decrease, but the amount of stars that can be formed per unit mass of gas decreases, leading to a reduction in the number of new stars formed. This study uses the ALMA-MaNGA Quenching and Star Formation (ALMaQUES) international observation project, combining the ALMA radio telescope and the MaNGA visible light project to observe dozens of galaxies undergoing “star formation quenching” to investigate the mechanisms of star formation quenching in galaxies. The study shows that both “reduced gas content” and “low star formation efficiency” play a role. In the central core (bulge) of galaxies, the main mechanism causing star formation quenching is “low star formation efficiency”, but in the outer disk of galaxies, both mechanisms need to be present together to induce the phenomenon of star formation quenching. Therefore, the causes of star formation quenching may be more complex than previously thought and cannot be explained by a single mechanism. Future research will focus on exploring the fundamental causes of “reduced gas content” and “low star formation efficiency”.
Figure 1: Galaxies Undergoing Star Formation Quenching