Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Notre Dame astronomers find massive supply of gas around modern galaxies

14.01.2013
Galaxies have a voracious appetite for fuel — in this case, fresh gas — but astronomers have had difficulty finding the pristine gas that should be falling onto galaxies.

Now, scientists have provided direct empirical evidence for these gas flows using new observations from the Hubble Space Telescope. The team led by Nicolas Lehner, research associate professor at the University of Notre Dame, is presenting its work today at the meeting of the American Astronomical Society in Long Beach, Calif.

The team's observations using Hubble's two ultraviolet spectrographs, the Cosmic Origins Spectrograph and the Space Telescope Imaging Spectrograph, show large quantities of cool gas with very low quantities of heavy elements in the gaseous cocoons surrounding modern galaxies. The lack of heavy elements indicates this gas in the circumgalactic medium of the galaxies has not been strongly processed through stars. The members' work, "The Bimodal Metallicity Distribution of the Cool Circumgalactic Medium at z

Led by Lehner, the team of astronomers identified gaseous streams near galaxies through the absorption they imprint on the spectra of distant, bright background quasars. The atoms in the gas remove small amounts of the light, and as the light from the quasars passes through the gas around galaxies, the chemical elements leave characteristic spectral "fingerprints" that allow astronomers to study the physical and chemical properties of the gas. Lehner and collaborators searched for the signature of gas within about 100,000-300,000 light-years of galaxies, identifying this gas due to its strong hydrogen absorption, a known signature of circumgalactic gas. They subsequently determined the amount of "metals" — all elements heavier than hydrogen and helium — in this gas to test whether the circumgalactic matter was being newly accreted from intergalactic space and lacking in metals or being ejected from the galaxies themselves and strong in metals.

"Astronomers have been searching for this infalling gas for a while," notes Lehner. "However, due to observational limitations, they had to search for metal-poor gas using the metals themselves. Since there is a tiny amount of metals in this gas, it was difficult to find in that way." The new work uses ultraviolet spectroscopy to identify the gas through its hydrogen absorption, which is independent of the metal content. This has allowed the team for the first time to determine how heavy elements are distributed around galaxies in an unbiased manner.

Lehner and colleagues estimated the amount of metals in the circumgalactic medium of galaxies over the last six billion years. They found that the distribution of heavy elements abundances in circumgalactic gas has two different characteristic values, around 2 percent and 40 percent of the heavy element content of the sun. Both branches of the metal abundance distribution have a nearly equal number of gas clouds. Meanwhile, the circumgalactic gas probed in this study was also found to have a mass comparable to that of all the gas within the galaxies themselves, thus providing a substantial reservoir for fueling continued star formation in modern galaxies. This study confirms the earlier finding by the same team that metal-enriched gas is widespread even far from the galaxies themselves, likely sent there by strong outflows driven by supernovae. The metal-rich gas likely traces winds and recycled gas from outflows and galaxy interactions. The metal-poor gas is in quantities of metals too low to trace even in very low-metallicity galaxies that are six billion years old or older. It very likely traces cold streams onto galaxies; its properties are in very good agreement with those seen in the computer simulations of galaxy formation and evolution.

"One of the big questions remaining from our study is what types of galaxies are associated with these gas clouds," remarks Lehner. The luminous components of most of the galaxies in the current study have not yet been identified. This team will use the Large Binocular Telescope, Keck and other ground-based telescopes to reveal the nature of the galaxies.

"Independent of the interpretation, our findings place new constraints on our understanding of how elements are distributed around galaxies," Lehner concludes. "There is not only a large mass of metal-rich gas around galaxies in the modern-day universe, but also a significant mass of metal-poor gas that may become available for star formation." This new work also implies the more diffuse intergalactic medium far from galaxies in the modern universe may be far more metal deficient than previously thought.

This research has been funded by NASA and the National Science Foundation, and has made use of the Hubble, Keck and Magellan telescopes. Co-authors include J. Christopher Howk from Notre Dame; Todd Tripp from the University of Massachusetts; Jason Tumlinson from the Space Telescope Science Institute (STScI); J. Xavier Prochaska from the University of California, Santa Cruz; John O'Meara from St. Michael's College; Chris Thom from STScI; Jess Werk from the University of California, Santa Cruz; Andrew Fox from STScI; and Joe Ribaudo from Utica College.

Nicholas Lehner | EurekAlert!
Further information:
http://www.nd.edu

More articles from Physics and Astronomy:

nachricht Tune your radio: galaxies sing while forming stars
21.02.2017 | Max-Planck-Institut für Radioastronomie

nachricht Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Impacts of mass coral die-off on Indian Ocean reefs revealed

21.02.2017 | Earth Sciences

Novel breast tomosynthesis technique reduces screening recall rate

21.02.2017 | Medical Engineering

Use your Voice – and Smart Homes will “LISTEN”

21.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>