Since 2017, the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) has been scanning the West Texas skies above the Davis Mountains to get spectroscopic data on Lyman-alpha frequency light from galaxies more than 10 billion light years away. Scientists can tell that new stars are being made quickly because these galaxies give off a unique wavelength of hydrogen light.
Using supercomputers and the help of thousands of citizen scientists across the world, researchers from The University of Texas at Austin have identified over 200,000 new celestial objects. They hope to map much more, then use that data to predict the fate of the cosmos.
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) has released its initial catalogue, which maps over 200,000 celestial objects, including distant stars and star-forming galaxies. HETDEX captures spectroscopic data by tiling the sky, which is used to calculate the precise location and distance from Earth of a star or galaxy.
The HETDEX cooperation team includes astronomers, engineers, technicians, and graduate students from six academic institutions in the United States and Germany.
Researchers have found more than 51,863 Lyman-alpha emitting galaxies at high redshift, 123,891 star-forming galaxies at lower redshift, 5,274 galaxies with no emission lines at low redshift, and 4,976 active galactic nuclei (AGN), which are bright spots that show the presence of black holes. For the first time, astronomical objects are being put into a list.
The catalogue’s outline was published in the Astrophysical Journal on February 7, 2023.
Erin Mentuch Cooper, a research scientist at The University of Texas at Austin and co-author of the study, said, “We’ve just blown up in terms of the number of redshifts we’ve recorded for the first time” (UT Austin). Cooper is in charge of the project’s data as the data manager.
The HETDEX catalogue is a treasure trove of information for astronomy research. Karl Gebhardt, a co-author on the study and the Herman and Joan Suit Professor of Astronomy at the University of Texas at Austin’s College of Natural Sciences, said, “That’s what I like about astronomy.” Gebhardt is the main scientist and person in charge of the project. Because a star’s frequency, which is similar to its colour, decreases as it moves away from Earth, like the sound of a train horn, redshift tells astronomers how fast a star is moving away from Earth.
The faster a star moves away, the further it is away. Hubble’s Law, which describes the relationship between speed and distance, may be used to locate the location of a galaxy, allowing researchers to create a 3D map of over 200,000 stars and galaxies using HETDEX.
This is just the beginning; it’s a small portion of what we will discover. According to Cooper, the ultimate goal of HETDEX is to map a million red-shifted galaxies.
Although HETDEX is a non-targeted survey that uses 35,000 fibre optic cables connected to the Visible Integral Field Replicable Unit Spectrograph to cover the sky, it varies from previous massive sky surveys (VIRUS).
Virus, like a prism, separates starlight from distant galaxies into its distinct colours. HETDEX tiles the sky, moving from place to spot and collecting 35,000 spectra in a moon-sized area. It collects between 500 and 600 hours of observations per year for its survey.
According to Gebhardt, we are conducting one of the time-consuming surveys utilising the world’s largest spectroscopic apparatus. To evaluate this data, we need the fastest computer we can locate, and TACC fits the bill. TACC handles all data storage and analysis for this big survey.
The TACC Corral data storage system gets data directly from the telescope through 100 Gigabit/second high-speed connections.
TACC has put in a lot of effort to assist us streamline our system, and it’s doing a fantastic job. We can process years of data in a few days or even a week using TACC technology. Gebhardt explained that they repeat the process because they are always refining and improving their operations.
The Maverick and Stampede2 supercomputers for HETDEX were provided by the Texas Advanced Computing Center, a leading academic supercomputing centre at UT Austin. Stampede2 is being funded by the National Science Foundation as a shared resource for thousands of scientists across the country. They participated with the processing and analysis of around 60 terabytes of image data on TACC’s Corral system.
Cooper and colleagues also worked with TACC to create public access to the data on JupyterHub.
Anyone with any academic credentials can sign up for a TACC account and see our data using a web browser. They will have complete access to all of our information. Right now, this is just a catalogue. However, HETDEX’s study will have a long-term impact. Cooper claims that TACC is cooperating with the setup.
An intriguing catalogue highlight is the identification of an active galactic nucleus (AGN) with significant Lyman-alpha light emission. Chenxu Liu, a postdoctoral astronomy researcher at UT Austin, supervised the study, which was published in The Astrophysical Journal in November 2022. It provides intriguing evidence of a black hole without a host galaxy.
This is an example of a “bare black hole,” as Gebhardt calls them.
Although nothing has been established, we believe these exist. They can only be detected by a survey such as HETDEX.
HETDEX science helps to a more thorough understanding of the universe’s extraordinarily fast expansion, which was discovered in 2019 by precise analyses of supernovae that act as cosmic yardsticks.
The Holy Grail for HETDEX is an accurate estimate of the rate of the universe’s expansion 10 billion years ago that will demonstrate the dark energy physics paradigm.
Astronomers dispute on how to characterise the measurement of the current expansion rate. To explain it, it may be necessary to modify the basic Big Bang hypothesis or the theory of gravity. It could have been caused by an unknown particle.
The current expansion rate can be compared to a precise value for the expansion rate early in the universe’s history. This comparison can tell us whether the Universe will continue to expand endlessly or if it will finally collapse on itself after billions of years.
According to Gebhardt, the entire goal of the HETDEX project is to quantify the expansion of the cosmos.
The HETDEX Collaboration is working incredibly hard in the coming year to deliver a definitive answer to the “million galaxy” question, and this new catalogue contributes significantly to that endeavour. Yet, there is a bigger picture at work here, and that is what we give back to the community—not just to scientists throughout the world, but to everyone in general. We would not be able to complete our assignment without TACC‘s supercomputing knowledge and resources since they provide us with the computing capabilities to perform multiple data analyses and continuously improve the technique.