Galaxies are getting killed in the extreme regions of the universe as their star formation is being closed and researchers are intrigued to know the reasons behind it. A new program termed as the Virgo Environment Traced in Carbon Monoxide survey (VERTICO) is investigating how the galaxies are being killed.
Toby Brown, the principal investigator of VERTICO led a team of 30 experts using the Atacama Large Millimeter Array (ALMA) for mapping the molecular hydrogen gas, the fuel from which new stars are created, at a very high resolution in 51 galaxies in the Virgo Cluster, the nearest galaxy cluster.
ALMA was commissioned in 2013 at a price of USD 1.4 billion. It is an array of connected radio dishes at a height of 5000 metres in Atacama Desert, Northern Chile. This is an international cooperation between the United States, Canada, Japan, Taiwan, Chile, South Korea and Europe. This is the largest astronomical project that is ground based and is the most advanced millimetre wavelength telescope to have been constructed. This is best suited to study cold gas clouds from which new stars are created that cannot be observed by visible light. Programs such as VERTICO are designed to address the issues leading to a major breakthrough in this domain.
The location of galaxies in the universe and their interaction with surroundings are major influences in their ability to form stars. But it is unknown how this environment rules on the life and death of the galaxies.
The galaxy clusters are the most massive environments in universe which contain many hundreds of galaxies. The presence of high gravitational forces results in high acceleration of the galaxies, superheating the plasma to extreme temperatures. In these dense interiors, galaxies interact with their surroundings that can kill their star formation. The main focus of VERTICO is to understand the mechanisms that remove star formation.
When galaxies fall through clusters, the intergalactic plasma can remove the gas in a very violent process known as ram pressure stripping. Clearing the fuel for star formation can result in killing the galaxy where no new stars are formed. The high temperature in clusters can stop the cooling and condensing of hot gas onto galaxies. Here the gas is slowly consumed as stars are formed leading to a gradual shut down in formation of stars known as strangulation.
These processes vary a lot but each leaves behind a unique imprint on the star forming gas of the galaxy. VERTICO aims to bring together a complete picture from each of these processes building on the previous work to understand the impact of environment on evolution of galaxy.
As Virgo Cluster is the nearest massive cluster, we can capture snapshots of the different stages of the galaxies. As a result, a complete picture of how star formation is shut in the cluster galaxies can be built. Virgo Cluster galaxies have been observed at nearly all wavelengths of the spectrum the observations of the star forming gas along with the required sensitivity do not exist as of now.
VERTICO aims to generate high resolution maps of the molecular hydrogen gas and understand the exact quenching mechanisms, ram pressure stripping responsible for killing the galaxies. This will improve the understanding of the evolution of galaxies in the densest places of the universe.