CSIRO’s ASKAP radio telescope is out of this world at finding new features of our Universe, even when those features are billions of years old.
The telescope at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory in Western Australia, is enabling a series of unique astronomy surveys led by researchers from around the world. One of these projects is called FLASH – First Large Absorption Survey in HI.
HI, or ‘H-one’, is the name scientists give to a specific emission produced by atoms of hydrogen. Hydrogen is the most abundant element in the Universe, so observing the gas helps astronomers identify the motion and properties of galaxies and informs our understanding of how galaxies form, grow and change over time.
FLASH is the largest study of its kind ever to be undertaken, and the first to look so deeply at a time-period – four to eight billion years ago, or about eight billion years after the Big Bang – in which astronomers know very little about the distribution of HI. It is also the first of ASKAP’s nine survey projects to hit a key milestone: the completion of observing with the telescope.
This means the FLASH team are now entering a new phase of the project, poring over the huge amounts of data on distant galaxies that has been collected by ASKAP.
Meet some of the team and hear about their journeys towards this milestone, and what it means for them.
Professor Elaine Sadler
Eminent academic Professor Elaine Sadler AO is an honorary fellow at CSIRO, a professor in astrophysics at the University of Sydney and one of the leaders of the FLASH survey.
She says FLASH is one of the most exciting, and complex, projects she’s worked on during her long career.
“There is a large cohort of undergraduate and postgraduate students who've worked with us over the years from all over the world,” Elaine says.
“Six of my research students have completed their PhDs as part of FLASH, and now there will be many more. It is so rewarding to be working with a complete set of data after so many years of planning.”
FLASH began 16 years ago when Elaine and her colleagues were wondering if it were feasible to use a telescope to examine the sky at different points at different intervals and time periods.
“The original concept for FLASH arose out of discussions I had on whether it was possible to use a telescope to search for the rare places in the distant
Universe where the HI gas was backlit by a bright radio source. I think ASKAP is still the only telescope able to carry out a survey like FLASH,” Elaine says.
CSIRO’s ASKAP radio telescope combines two features essential to FLASH: a radio-quiet site at the observatory and the ability to see a large section of the sky, referred to as a wide field of view. The radio-quiet site allows the team to detect faint signals from way back in time, and the wide field of view allows them to search across huge volumes of space to find the rare signals they are looking for.
“There’s a huge team working behind ASKAP and making this science possible,” Elaine says.
“The engineers who developed the wide field of view technology; the operations team keeping ASKAP running every day and night; the scientific computing, IT and data groups that manage the software and tools which enable us to work with the immense amount of data that we have.”
Finishing observing with ASKAP really is a momentous occasion for Elaine, having been there since the idea for the survey was formed.
“Where we are today is certainly not the end, because we now have literally thousands upon thousands of terabytes of processed data in the CSIRO archives.
This is really a unique treasure trove of information about galaxies in the distant universe that will keep us busy for years and years to come.”
Dr Elizabeth Mahony
Elizabeth Mahony, a CSIRO research scientist and one of the leaders of the FLASH survey, was a PhD student when Elaine first submitted the FLASH proposal. She became involved in 2015 when experimental observations were being made with six of ASKAP’s 36 dishes.
“For a long time, our focus has been on the technical side – getting the observations right, processing the data, making sure everything works as it should,” says Elizabeth.
The FLASH team made discoveries of hydrogen gas clouds in and around galaxies of the distant Universe right from the start. These gas clouds represent the building blocks from which new generations of stars can form. The gas can also fall into supermassive black holes, triggering powerful radio jets that can be observed with ASKAP. These black holes are so distant that, in many cases, the radio signals originated long before our Sun existed.
When these ancient galaxies were observed in 2015, it showed that ASKAP could detect galaxies invisible to other telescopes and that the scope of the project, outlined years earlier by Elaine, would be possible.
Elizabeth says FLASH has been a huge part of her research career so far.
“At the simplest level, it’s given me the opportunity to learn something new about the Universe, but more than that, it’s let me step into a leadership role on a genuinely large and complex survey. Leading the team and helping steer something of this scale has been a huge privilege.
“I like discovering new things, solving the puzzles posed by getting new data, while also enabling and supporting others to do great science.”
Emily Kerrison
Emily Kerrison is one of Elaine’s students at the University of Sydney and CSIRO, who has just been awarded her PhD. As part of her doctorate research, Emily, used FLASH observations to solve the 35-year-old case of a questionable quasar.
Quasars are galaxies that have a very active supermassive black hole in their centre, making them very bright to radio telescopes. The quasar Emily studied is extremely far away and appeared to be emitting a varying pattern of light, or twinkling. It was thought to be the smallest quasar ever detected that Emily and her colleagues revisited in their recent study.
“In the 1990s, it was known that there was a distant quasar with a hint of a galaxy along our line of sight, but the data wasn’t good enough to identify the galaxy’s distance or composition,” Emily says.
“Through FLASH, we identified hydrogen gas at the location of this original galaxy, and we made an unexpected discovery of another two galaxies along the line of sight as well.”
Using ASKAP observations and optical data from the Gemini telescope, the team’s work showed there were three separate galaxies directly between us and the quasar – distorting its size and behaviour.
Emily has delved even deeper into the case, using data archives of observations from other CSIRO telescopes to fill in the 35-year time gap. She has collected more information on this complex interplay across time and space and how it appears to us on Earth, revealing periods where the quasar was brightly shining, but no further evidence of the twinkling. Investigations are still ongoing as to whether this could be the smallest radio quasar, and the team is already planning how best to test this theory with additional observations.
“Without these questions being re-ignited with the FLASH observations, we would never have thought to explore deeper and find such interesting results,” Emily says.
Having just submitted her PhD, Emily says it seems like there are a million things to get involved in and look forward to as a result of the project.
“Now that the FLASH survey is complete, we’re going to have thousands more targets like this one that need a closer look.
“Soon I’ll be heading to ESO – the European Southern Observatory, an intergovernmental organisation that operates three observing sites in Chile – where I’ll be thinking about more ways we can combine FLASH data with optical observations to better understand all the weird and wonderful galaxies out there in the Universe.”
Looking back to the future
FLASH is only one of nine major surveys being conducted with the ASKAP radio telescope. There’s a team of researchers just like Elaine, Elizabeth and Emily behind each survey, shining a light on different mysteries of our Universe.
From hydrogen gas in galaxies 8 billion years old, to strangely behaving black holes, there is so much exciting science still to come.