Silhouettes of early galaxies reveal few seeds for new stars

Silhouettes of early galaxies reveal few seeds for new stars
Artist's impression of the gas surrounding a young galaxy in the distant universe. The gas, shown as red streams on the left, is actually invisible, and the starlight from the galaxy is too faint for astronomers to see directly. Instead, the gas is seen in silhouette against a bright, background quasar. Molecules in the gas imprint a shadow, or absorption line, onto the quasar light at a very specific colour, as seen on the right, and astronomers can detect this shadow. Credit: Swinburne University of Technology

( —An international team of astronomers has discovered that gas around young galaxies is almost barren, devoid of the seeds from which new stars are thought to form – molecules of hydrogen.

Without starlight to see them directly, the team – including Associate Professor Michael Murphy from Swinburne University of Technology – observed the young galaxies' outskirts in silhouette.

They searched for telltale signs of absorbing the light from background objects called quasars – sucking in surrounding material – that glow very brightly.

"Previous experiments led us to expect molecules in about 10 of the 90 young galaxies we observed, but we found just one case," Associate Professor Murphy said.

Astronomers believe that begin to form in cold gas that is rich in molecules. The team observed galaxies at a time when the Universe was most actively forming stars, about 12 billion years ago.

"This is a little mystery. This is when most stars are born, and we think this gas forms stars eventually, but it lacks the key ingredient – – to do so," Association Professor Murphy said.

The team believes that location and time are the key.

"The gas we observe in silhouette probably lies too far from the galaxies to form stars," co-leader of the study, the University of Hawaii at Manoa's Dr Regina Jorgenson said.

"It's got lots of potential, but it hasn't had time to fall into the richer, denser parts of the galaxies which might be better stellar nurseries."

The researchers made new observations of more than 50 quasars for this study using the 6.5 metre diameter Magellan telescopes in Chile.

The study will be published in the Monthly Notices of the Royal Astronomical Society and is available online at

It was conducted by researchers from the University of Hawaii, Swinburne University of Technology, The University of Cambridge and the University of Arizona.

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Citation: Silhouettes of early galaxies reveal few seeds for new stars (2014, July 14) retrieved 23 October 2019 from
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Jul 15, 2014
Dear Regina and Michael, that the gas you need for stars would still be far out, really does not look convincing. What helps out is to assume that the gas is concentrated in blobs. This idea already explains every week one of these posts, so it is stunning that this view is not generally accepted. In your case: it is all there, but you don't notice: Stars will be formed while your quasar light is not affected, since there is much space in between the small blobs. Wanna know more? Search for "gravitational hydrodynamics". Thanks, your observations provide a great support for it.

Jul 15, 2014
'a little mystery' indeed for the merger maniacs. Young galaxies grow from the core, out, not the reverse. Duh... But then, recognizing this fact will embarrass too many intellectual egomaniacs. And that just won't do. So off with their heads. Merger mania continues unabated, despite the mounting evidence to the contrary.

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