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Herschel digs the dust
on galaxies

Posted: 25 April 2011

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The Herschel Space Observatory has been used to help astronomers at Cardiff, Nottingham University and Max-Planck Institute for Astrophysics to understand the amount of dust in galaxies at varying distances, it was heard at the National Astronomy Meeting held in Llandudno, North Wales, last week.

Dr Haley Gomez of Cardiff University, who presented the results at the conference, along with her colleagues, used data taken from the Herschel Astrophysical Terahertz large Area Survey, H-ATLAS, to take a look at the evolution of dust in galaxies over the past five billion years of cosmic history. H-ATLAS is the largest key astronomical project on ESA’s Herschel Space Observatory and surveys an amazing 550 square degrees of sky. With both its PACS and SPIRE cameras which snap pictures in the infrared and submillimetre wavebands, astronomers are able to unveil the cold Universe, studying the dusty cosmos in high detail. To tell us more about dust and Herschel, Astronomy Now reporter Gemma Lavender interviews Cardiff University’s Dr Haley Gomez in the video report below.

Now, the survey has provided Gomez and her team with an insight into the Universe, where they found that the galaxies they studied were dominated by cold dust with temperatures between 15 to 25 kelvin (–258 to –248 degrees Celsius). Their observations also revealed that the dust masses for large galaxies were about five times larger at redshifts of around 0.5 compared to galaxies which can be found in the local universe. The collaboration between the three institutions has also revealed that the mass of dust to stellar mass was three to four times larger in the past. The source of this interstellar dust is still uncertain and difficult to explain with standard models.

But why is this cold dust relevant? Dust contributes one percent of the mass of a galaxy but despite this small amount, it allows stars to form more efficiently. Without these cosmic particles, we would not have molecular hydrogen, which means no water traces in galaxies. “We’re talking about the building blocks of asteroids, the cores of comets and rocky planets,” says Gomez. “But we’re also talking about the building blocks of us – life is lumps of dust, of iron and carbon and so on, inside ourselves. So when you ask where dust comes from you’re asking where planets come from and where life comes from.”

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