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Ionized Hydrogen Gas


The answer lies outside of the galaxy in the form of ionized hydrogen gas the ... of matter was Helium, 1/10% of deuterium, and traces of lithium and beryllium ... – PowerPoint PPT presentation

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Title: Ionized Hydrogen Gas

Ionized Hydrogen Gas
The Intergalactic Medium
  • While looking inside galaxies for the the main
    constituent of mass, we can not account for more
    than half of all normal baryonic matter.
  • The answer lies outside of the galaxy in the form
    of ionized hydrogen gas the Intergalactic

Formation of Protons
  • The Hadron Epoch One second after the big bang…
  • The universe cools down enough for protons and
    neutrons to form
  • Nucleosyntheseis 100 Seconds after the Big Bang…
  • The universe cools down enough for protons and
    neutrons to fuse to create heavier elements such
    as Hydrogen and Helium
  • Three minutes after nucleosynthesis began, the
    temperature cooled down so much that nuclear
    fusion could no longer take place. The relative
    abundances of matter were 75 of matter was
    Hydrogen, 25 of matter was Helium, 1/10 of
    deuterium, and traces of lithium and beryllium

Large Scale Structures
  • In the early universe, matter was spread mostly
  • Density enhancements led to matter condensing.
  • This condensing is what led to galaxy formation.
    This took place 10 million years after the Big

Determining the Amount of Baryons in the Universe
  • Recall that in the Big Bang nucleosynthesis,
    deuterium, a heavy isotope of hydrogen was formed.
  • Deuterium is very easy to destroy.
  • A certain amount of energy is needed by a photon
    to destroy the deuterium

What this means
  • Deuterium will cease to be destroyed once the
    universe expands to a certain point.
  • Recall that light seems to interact only with
    baryonic matter.
  • Astronomers can calculate the baryon to photon
    ratio from observing the abundance of deuterium
    in the universe.

What is found
Type of Material
Percentage of Baryonic Matter
Stars 10
Gas in Galaxy Clusters 6
Cold Intergalactic Gas 24
Cold Gas in Galaxies 2
  • This implies that over half of all baryonic
    matter is unaccounted for with just stars, gas in
    galaxy clusters, cold intergalactic gas, and cold
    gas in galaxies
  • Astronomers continue to this day to increase
    precision of such calculations

Efficiency of Structure Formation
  • Simulations have shown that galaxy formation does
    not efficiently consume all primordial material.
  • Not all material around galaxy formation is
    accreted into the galaxy
  • During galaxy formation, as matter falls into the
    galaxy, a shock wave is sent outward. This shock
    wave will carry enough energy to shock heat any
    material that may lie outside of the galaxy.
  • It is now suspected that a majority of the
    primordial matter exists outside of galaxies and
    has been ionized by this shock wave.

The Intergalactic Medium
Shock heating should heat the intergalactic
medium to 105 107 Kelvin.
Ionized Hydrogen Gas
  • An atom has a nucleus where protons and neutrons
  • In the case of a hydrogen atom, there is simply a
    proton in the nucleus of the atom
  • A single electron is bound to the atom.
  • Ionized hydrogen is hydrogen that has had the
    electron stripped away from the atom.

Ionization of Hydrogen
  • Once hydrogen has been ionized, there is no
    longer any electrons to absorb or release energy
    (no way to emit or absorb photons).
  • This makes detecting ionized hydrogen in the
    intergalactic medium nearly impossible.

  • Recall that there were other elements that were
    created early in the universe that should be
    present in the intergalactic medium.
  • Using other constituents of the intergalactic
    medium, astronomers are finally detecting this
    mass of material outside of galaxies.

Quasars and Absorption
  • Helium requires higher temperatures than hydrogen
    to be ionized.
  • FUSE Far Ultraviolet Spectroscopic Explorer
  • FUSE uses distant quasars as a background source
    against the IGM, to look for absorption of the
    quasars light by helium, the second most abundant
    element of the IGM
  • Other material is suspected to exist in the IGM
    as a result of supernovae explosions sending
    heavy elements off with enough energy to escape
    the galaxy.

  • Amount of mass of HII suspected to exist
  • 5.4E10 Solar Masses 1.0692E41 kg
  • If dark matter were all HII
  • We would expect a mass of 9E10 Solar Masses
  • Thats 1.07E68 atoms.
  • A density of 5E55 pc-3, 1.7E06 m-3
  • 5.96E36 atoms would pass through the Solar
    System each second
  • 3.83E24 Atoms would pass through the Earth each

  • Burles, Scott . "Sharpening the Predictions of
    Big-Bang Nucleosynthesis." . 14 01. 1999.
    American Physics Society. 18 04. 2007
  • Fukugita, M.. "The History of Galaxies." Nature
    06 06. 1996 489 - 495.
  • Krauss, Lawrence M. . "Cosmological Antigravity."
    Scientific American 01. 1999 53 - 59.
  • Kriss, Gerard . "FUSE Observes the Intergalactic
    Medium." FUSE Science Summaries. 15 02. 2005.
    NASA. 18 04. 2007 lthttp//
  • Nath, Biman B. . "Heating of the Intergalactic
    Medium as a Result of Structure Formation." . 10
    05. 2001. Royal Astronomical Society. 18 04.
    2007 lthttp//
  • Romeel, Davé. "Baryons In The Warm-Hot
    Intergalactic Medium." . 10 05. 2001. The
    Astrophysical Journal. 18 04. 2007