This is a neat solution to the problem and provides important data.
In my cloud cosmology, what is produced is hydrogen and only hydrogen
and all else is a product of star formation. It is worthwhile to
know that we have a natural and continuing balance of mass between
the galaxy and the surrounding envelop which is real is itself as an
artifact of the gravitational fields. It is plausible to posit an
internal steady state of star creation and star destruction for every
individual galaxy with little at play between galaxies.
Not enough though to make an anti galaxy a good idea though.
At least we now have direct insight into the make up of all that gas.
Notre Dame
astronomers find massive supply of gas around modern galaxies
by Staff Writers
Notre Dame IN (SPX) Jan 16, 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 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<1 astrophysical="astrophysical" been="been" has="has" i="i" journal.="journal." submitted="submitted" the="the" to="to">
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
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