Gamma Rays from distant Galaxy seen by NUI Galway Astronomers

Dec 16 2015 Posted: 15:47 GMT

Radiation from a very distant galaxy has been detected by the VERITAS telescopes in Arizona, surprising astronomers. This galaxy is so far away that the radiation has been traveling toward us for at least 7.6 billion years, ultimately reaching Earth.

In April 2015, after traveling for half the age of the Universe, a flood of powerful gamma rays from the galaxy PKS 1441+25 generated a torrent of light in our atmosphere that was captured by the VERITAS (Very Energetic Radiation Imaging Telescope Array System) cameras. VERITAS uses a system of four 12-metre diameter mirrors and cameras that takes 500 billion “pictures” every second. They detected very-high-energy gamma rays, with energies tens of billions of times the energy of ordinary visible light. Details of the detection have been published in Astrophysics Journal Letters.

The primary analysis of the VERITAS data was carried out at NUI Galway’s Centre for Astronomy. Dr Mark Lang, a corresponding author on the scientific letter commented: “We were surprised to detect very-high-energy radiation from such a distant object. We had expected that it would be absorbed by the extra-galactic background light (EBL), a type of cosmic fog that fills the Universe. This allows us to make an important measurement of the light emitted by all stars over the history of the Universe.”

PKS 1441+25 is a quasar in which material swirls into a super-massive black hole which has a mass of millions of times that of the Sun. Some of the material gets channeled into jets and propelled outwards at almost the speed of light. We are looking down the barrel of one of these jets.

PKS 1441+25 is one of the farthest sources of very-high-energy gamma rays ever to be detected by ground-based instruments like VERITAS. The galaxy was also detected by NASA’s Fermi satellite and the MAGIC observatory based in the Canary Islands.

NUI Galway undergraduate astronomy students Crystal Cloherty and Adam Moylan had the opportunity to study the PKS 1441+25 data as part of a University summer research internship programme. “We were thrilled to think we were looking at an outburst of radiation that happened when the Universe was only half its current age”.

Co-author Dr Gary Gillanders from the Centre for Astronomy remarked
“For a number of years Ireland has had no national funding scheme to support fundamental research of this type; it has been a real challenge for us to participate in an international scientific collaboration. Following the publication of the Government’s new science strategy we eagerly look forward to the re-emergence of financial support for basic research. This is essential if we want our students to be exposed to cutting-edge discoveries.”

VERITAS is an international collaboration of over thirty institutions in the US, Canada, Germany and Ireland, including NUI Galway, UCD and Cork IT.


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