Periodic Reporting for period 2 - MeerGas (Finding the Origin of Gas in Galaxies with MeerKAT)
Período documentado: 2022-04-01 hasta 2023-09-30
Spiral galaxies like our Milky Way continuously form new stars. These form from the hydrogen gas that is also present in the galaxy. Small gas clouds can collapse due to their own gravity and eventually ignite as new stars. However, if there is no new gas coming into the galaxies, star formation will stop and they will fade to become “dead” galaxies. By measuring how many stars are formed per year and how much gas there still is, we can work out that for nearby spiral galaxies the gas supply will run out in one or two billion years. But spiral galaxies are not “dead”: we know that they have been forming stars for almost the entire lifetime of the universe, often at a much higher rate, so they must have an external supply of gas.
It turns out that there is a large amount of hot gas between galaxies that could be accreted by the galaxies if it cools enough to be captured. The hot gas is difficult to observe, but as the gas cools it should become visible as neutral hydrogen and be observable with radio telescopes. Many attempts have been made over the years to detect this accreting neutral hydrogen, but no unambiguous detection has ever been made.
Does this mean our understanding of how galaxies evolve is wrong? Computer simulations suggest that the gas is in extremely diffuse filaments surrounding the target galaxies and could not have been observed with the previous generation of radio telescopes. The new MeerKAT radio telescope in South Africa will change this. It is much more sensitive and can produce radio images of a much higher quality.
We are observing 30 nearby galaxies with MeerKAT and will produce radio images that are almost a hundred times more sensitive than any previous observations of these galaxies.
Over the last two years we have been processing our data. We also have been working on computer algorithms to analyse these data as the extreme sensitivity of the new observations demands novel high-precision algorithms. In the last few months we have produced our first full-sensitivity images and we are now studying them, looking for signs of the very diffuse gas that is predicted to be present around the galaxies. In the next phase of this project we will confirm or rule out the existence of these accreting gas filaments. This will eventually lead to a much better understanding of how galaxies get their gas, and form a fundamental component in improving our understanding of how galaxies and the universe evolve.
It turns out that there is a large amount of hot gas between galaxies that could be accreted by the galaxies if it cools enough to be captured. The hot gas is difficult to observe, but as the gas cools it should become visible as neutral hydrogen and be observable with radio telescopes. Many attempts have been made over the years to detect this accreting neutral hydrogen, but no unambiguous detection has ever been made.
Does this mean our understanding of how galaxies evolve is wrong? Computer simulations suggest that the gas is in extremely diffuse filaments surrounding the target galaxies and could not have been observed with the previous generation of radio telescopes. The new MeerKAT radio telescope in South Africa will change this. It is much more sensitive and can produce radio images of a much higher quality.
We are observing 30 nearby galaxies with MeerKAT and will produce radio images that are almost a hundred times more sensitive than any previous observations of these galaxies.
Over the last two years we have been processing our data. We also have been working on computer algorithms to analyse these data as the extreme sensitivity of the new observations demands novel high-precision algorithms. In the last few months we have produced our first full-sensitivity images and we are now studying them, looking for signs of the very diffuse gas that is predicted to be present around the galaxies. In the next phase of this project we will confirm or rule out the existence of these accreting gas filaments. This will eventually lead to a much better understanding of how galaxies get their gas, and form a fundamental component in improving our understanding of how galaxies and the universe evolve.
Our MeerKAT radio telescope observations started at the same time as this project. These observations consist of 1650 hours of telescope time, resulting in over a petabyte of radio data. We therefore concentrated on developing an automated pipeline that would create radio images from the radio telescope data with a minimum of human intervention. As part of this work we developed an automated procedure that creates diagnostic plots and tables and automatically formats and uploads these to a repository where our team can inspect them. The full-depth images are created by combining many individual observations. Even on a large computing cluster every iteration of this process takes two to three weeks per galaxy. We therefore developed a procedure that automatically takes these individual images, forms a combined image and extracts science-ready data products, all without human intervention.
At this time we have full-sensitivity data of 13 galaxies. We have been processing these to create final images, and our team is now in the process of analysing these, searching for the very faint gas in the outer parts of these galaxies. A number of scientific papers on these are now being written and we expect that first-look images from the project will be released to the public in the next few months.
At this time we have full-sensitivity data of 13 galaxies. We have been processing these to create final images, and our team is now in the process of analysing these, searching for the very faint gas in the outer parts of these galaxies. A number of scientific papers on these are now being written and we expect that first-look images from the project will be released to the public in the next few months.
Our observations are the deepest and most detailed radio images ever taken of these galaxies. They are about one hundred times deeper than the previous generation of observations and are showing us features in these galaxies never seen before. The observations have been designed to reach the sensitivities needed to detect the diffuse gas filaments that fuel the galaxies - if they exist! We have now started the analysis of these deep images, and at the end of the project will be able to definitively confirm or rule out whether this is how galaxies evolve. Our results will inform studies of galaxy evolution at least for the next decade and form the foundation for future, even more sensitive observing projects that will be done with the Square Kilometre Array which will be online early next decade.