How do galaxies fade?

The seemingly immutable galaxies are in a state of flux motivated by various factors that drive their evolution. Among them stands out the formation of stars, which are born from large and cold clouds of molecular gas and whose abundance depends on the available gas.

The MASCOT project, promoted by the European Southern Observatory (ESO) and with the participation of the Institute of Astrophysics of Andalusia (IAA-CSIC), was born to study this cold gas, essential for understanding galactic evolution. As a legacy, or public and open release of data, the project has just released its first results, with detailed observations of some two hundred galaxies.

“The galaxies that we observe in the current universe exhibit a wide variety of properties, but they are usually classified as blue and red, that is, galaxies that form stars and dim galaxies where stars are barely being born. Few galaxies show intermediate characteristics and are located in the so-called “green valley”, which poses a problem: if the process of galactic evolution were simply a matter of slow gas depletion, we would expect to see many more galaxies in the green valley. Thus, some mechanism must be stopping star formation, making the transition from blue to red relatively fast.”points out Sara Cazzoli, a researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who participates in the project.

MaNGA Database Galaxy Ensemble

MASCOT, led by Dominika Wylezalek (University of Heidelberg), will study in detail a set of galaxies from the MaNGA (Mapping of Nearby Galaxies at Apache Point Observatory) database, a project that observed ten thousand galaxies and contributed two-dimensional maps of, for example, the speed and age of stars in galaxies, the abundance of elements or the rate of star formation.

However, MaNGA did not provide data on the cold phase of the gas, and therein lies the objective of MASCOT, which will study the content of molecular gas available for star formation, as well as the relationship between the properties of molecular gas, such as its mass and kinematics, and the rate of formation and composition of stars.

In this first series of data, the scientific team has observed that, by relating the mass of molecular gas to stellar ages, galaxies with less gas tend to show older stellar populations near the galactic center, which is an indication that the The quenching of galaxies, or the change from blue to red, occurs from the inside out.

Cooling

“To explain this cooling, feedback due to the activity of supermassive black holes and/or the violent formation of stars is being explored. These processes can trigger the formation of large gas movements, the galactic superwinds, thus heating the cold interstellar medium. In this way the formation of stars is slowed down or, in the most extreme cases, ceases, first in the center of the galaxies and then in the most peripheral zones”points out Sara Cazzoli (IAA-CSIC).

The MASCOT survey is conducted from the Arizona Radio Observatory (ARO), a forty-foot antenna capable of detecting the cold gas, and this data release represents just over half of the 1,400 observation hours available. The total sample studied will be about 250 or 300 in total.

Font: IAA, DICYT,

Reference article: https://www.dicyt.com/noticias/las-galaxias-se-apagan-de-inside-outside