The Violent Lives of Galaxies

Editorial, 20th January 2018

The much-debated question of the origin of the Universe has stemmed several explanations over the years. Astronomy, one of the oldest natural sciences in history, has shaped human existence and culture in a variety of ways. Seeking answers to questions in the stars above—romantic as the allusion may be—the key to the origin of our universe lies within them. The road to discovery continues to broaden every passing day—the exponential rate of technological innovations across the world are bringing us closer to the answers we yearn for.

 

Dr Meghan Gray, an associate professor at the University of Nottingham, is an observational extragalactic astronomer with interests in the fields of galaxy evolution and large-scale structure of the universe. She and her team have been working on a multiwavelength project with the goal of exploring galaxy evolution across a wide range of environments and luminosity, known as The Space Telescope A901/902 Galaxy Evolution Survey, or STAGES.

In a recent web-talk conducted at IIT Roorkee, she outlined the ideas behind the project. By exploring galaxy clusters and superclusters, their aim was to connect galaxies within galaxy clusters with their environment. The galaxy environment is affected by the neighbouring galaxies, the amount of hot gas it ploughs through, as well as the amount of dark matter surrounding it. All these factors influence the shape, colour, rate of star formation as well as the existence of an active galactic nuclei (AGN) of individual galaxies within the cluster.

 

STAGES has observed the Abell 901/902 supercluster with many of the world’s most powerful telescopes, such as the Hubble Space telescope, covering wavelengths from the X-ray all the way to the radio. The 80 different images taken by the Hubble telescope, when stitched together, showed more than 60,000 galaxies. Through these pictures, the STAGES team mapped dark matter regions using gravitational lensing, as well as discovering the populations of “red spiral” galaxies, a crucial discovery serving as the missing link in the stages of galactic evolution. These discoveries served as key points in determining how the evolution of galaxies is not just affected by their date of origin, but also by their immediate environment.

 

A self-admittedly optimistic wishlist shared by Prof. Meghan during the talk provided a glimpse of what astronomers and researchers are looking forward to in this field. With data spanning several billion years of time evolution and a full 3D view of the universe being the most difficult ones, the professor talked on how computer based simulation is helping them understand the nature and interaction of visible matter, dark matter and dark energy (comprising 5%, 27% and 68%, respectively of the universe) in the galaxy clusters. A hydrodynamical simulation of a galaxy cluster developed by one of Prof. Meghan’s PhD student Jake Arthur[1] has provided them with valuable insights about the presence of an obvious filamentary structure surrounding the cluster.

 

The emergence of fields like Big Data and the incorporation of more powerful telescopes, which promise to image the universe better, has opened new frontiers for the field. The Galaxy Zoo Program, modestly termed as a citizen science project, demonstrates the prowess of the combination of internet, data, and the human brain. Classification and segregation of galaxies based on their structure and composition is an important step for understanding their formation and evolution. Pushing out images of millions of galaxies to the open internet, the project asks citizen scientists to classify galaxies based on various parameters. Started in 2007, the Galaxy Zoo Project has already become the one with the highest number of publications among all other projects of similar nature.

 

Large datasets, computers with petaflops of computational power and, most importantly, initiatives such as STAGES and the Galaxy Zoo Project are converting astronomy into an open, and yet, a more interesting field than it has ever been. Now, it has become all the more essential to reinforce and expand all kinds of collaborative initiatives, large-scale or interdisciplinary, in order to foster to new research and unravel the scintillating truths lurking behind the dusky night skies.

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