Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Recycling galaxies caught in the act

14.03.2012
When astronomers add up all the gas and dust contained in ordinary galaxies (like our own Milky Way), they find a discrepancy: there is not nearly enough matter for stars to form at the observed rates for long.

As a (partial) solution, a matter cycle on gigantic scales has been proposed. In our local galactic neighbourhood, traces of this mechanism had already been found. Now, a study led by Kate Rubin of the Max Planck Institute for Astronomy has found the first direct evidence of such gas flowing back into distant galaxies that are actively forming new stars, validating a key part of "galactic recycling".


Images of the six galaxies with detected inflows taken with the Advanced Camera for Surveys on the Hubble Space Telescope. Most of these galaxies have a disk-like, spiral structure, similar to that of the Milky Way. Star formation activity occurring in small knots is evident in several of the galaxies' spiral arms. Because the spirals appear tilted in the images, Rubin et al. concluded that we are viewing them from the side, rather than face-on. This orientation meshes well with a scenario of 'galactic recycling' in which gas is blown out of a galaxy perpendicular to its disk, and then falls back in at different locations along the edge of the disk.
Image credit: K. Rubin, MPIA

Star formation regions, such as the Orion nebula, represent some of the most beautiful astronomical sights. It is estimated that in our home galaxy, the Milky Way, on average one solar mass's worth of matter per year is turned into stars. Yet a survey of the available raw material, clouds of gas and dust, shows that, using only its own resources, our galaxy could not keep up this rate of star formation for longer than a couple of billion years. Is our home galaxy currently undergoing a rather special, comparatively short-lived era of star formation? Both stellar age determinations and comparison with other spiral galaxies show that not to be the case. One solar mass per year is a typical star formation rate, and the problem of insufficient raw matter appears to be universal as well.

Evidently, additional matter finds its way into galaxies. One possibility is an inflow from huge low-density gas reservoirs filling the intergalactic voids; there is, however, very little evidence that this is happening. Another possibility, closer to home, involves a gigantic cosmic matter cycle. Gas is observed to flow away from many galaxies, and may be pushed by several different mechanisms, including violent supernova explosions (which are how massive stars end their lives), and the sheer pressure exerted by light emitted by bright stars on gas in their cosmic neighbourhood.

As this gas drifts away, it is pulled back by the galaxy's gravity, and could re-enter the same galaxy in time scales of one to several billion years. This process might solve the mystery: the gas we find inside galaxies may only be about half of the raw material that ends up as fuel for star formation. Large amounts of gas are caught in transit, but will re-enter the galaxy in due time. Add up the galaxy's gas and the gas currently undergoing cosmic recycling, and there is a sufficient amount of raw matter to account for the observed rates of star formation.

There was, however, uncertainty about the viability of this proposal for cosmic recycling. Would such gas indeed fall back, or would it more likely reach the galaxy's escape velocity, flying ever further out into space, never to return? For local galaxies out to a few hundred million light-years in distance, there had indeed been studies showing evidence for inflows of previously-expelled gas. But what about more distant galaxies, where outflows are known to be much more powerful – would gravity still be sufficient to pull the gas back? If no, astronomers might have been forced to radically rethink their models for how star formation is fueled on galactic scales.

Now, a team of astronomers led by Kate Rubin (MPIA) has used the Keck I telescope on Mauna Kea, Hawai'i, to examine gas associated with a hundred galaxies at distances between 5 and 8 billion light-years (z ~ 0.5 – 1), finding, in six of those galaxies, the first direct evidence that gas adrift in intergalactic space does indeed flow back into star-forming galaxies. As the observed rate of inflow might well depend on a galaxy's orientation relative to the observer, and as Rubin and her team can only measure average gas motion, the real proportion of galaxies with this kind of inflow is likely to be higher than the 6% directly suggested by their data, and could be as high as 40%. This is a key piece of the puzzle and important evidence that cosmic recycling ("galactic fountains") could indeed solve the mystery of the missing raw matter.

Contact

Dr. Kate Rubin (lead author)
Max Planck Institute for Astronomy
Heidelberg, Germany
Phone: (+49|0) 6221 – 528 370
Email: rubin@mpia.de
Dr. Markus Pössel (Public relations)
Max Planck Institute for Astronomy
Heidelberg, Germany
Phone: (+49|0) 6221 – 528 261
Email: pr@mpia.de

Dr. Markus Pössel | Max-Planck-Institut
Further information:
http://www.mpia.de

Further reports about: Milky Way Recycling distant galaxies massive star raw material star formation

More articles from Physics and Astronomy:

nachricht Gamma-ray flashes from plasma filaments
18.04.2018 | Max-Planck-Institut für Kernphysik

nachricht How does a molecule vibrate when you “touch” it?
17.04.2018 | Universität Regensburg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

Im Focus: The Future of Ultrafast Solid-State Physics

In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.

Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...

Im Focus: Stronger evidence for a weaker Atlantic overturning

The Atlantic overturning – one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards – is weaker today than any time before in more than 1000 years. Sea surface temperature data analysis provides new evidence that this major ocean circulation has slowed down by roughly 15 percent since the middle of the 20th century, according to a study published in the highly renowned journal Nature by an international team of scientists. Human-made climate change is a prime suspect for these worrying observations.

“We detected a specific pattern of ocean cooling south of Greenland and unusual warming off the US coast – which is highly characteristic for a slowdown of the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Improved stability of plastic light-emitting diodes

19.04.2018 | Power and Electrical Engineering

Enduring cold temperatures alters fat cell epigenetics

19.04.2018 | Life Sciences

New capabilities at NSLS-II set to advance materials science

18.04.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>