Intergalactic medium is a lecture and an article studying the entity that exists between galaxies. It is also a mini-lecture for a quiz section as part of the astronomy department course on the principles of radiation astronomy.

UGC 5101 is a peculiar galaxy with a single nucleus contained within an unstructured main body that suggests a recent interaction and merger. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University).

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Quiz edit


1 Yes or No, An intergalactic medium is a medium in between interplanetary and interstellar media.


2 Complete the text:

Match up the item letter with each of the possibilities below:
Intracluster medium - A
Mayall's object - B
M82 PAHs - C
Milky Way bubbles - D
Local Hot Bubble - E
Stephan's Quintet - F
UGC 8335 - G
Arp 272 - H









3 True or False, An intergalactic medium is a rarefied plasma rather than a gaseous medium.


4 Which of the following is not a characteristic of X-radiation in the IGM?

X-rays come from the IGM
an X-ray background
shock heating
secondary ionizations and excitations
far more likely to be absorbed by He I rather than H I

5 Do we know enough about the intergalactic medium to trust measurements of background sources seen through foreground


6 Complete the text:

Whether the thermal IGM is

or collisionless at scales smaller than the scale

scale depends on the effect of reduced

that is mediated by the plasma


7 True or False, Star clusters have been discovered to occur outside a galaxy.


8 Which of the following are phenomena associated with strong forces in the IGM?

stochastic acceleration
hottest clusters
scaling of the acceleration efficiency with IGM temperature
collisionless IGM
placid magnetic compressions
the smaller the mean free path
cold regions
least effective for inducing the instability

9 True or False, O VI is a lithium-like ion.


10 Which of the following are phenomena associated with electromagnetic cascades?

spectral and timing properties of astronomical sources
very high-energy γ-rays
the way from the source to the Earth
soft X-rays
ambient radiation fields inside the γ-ray source
source stability

Hypotheses edit

  1. The research of the intergalactic medium is under primarily astronomy branches astrochemistry and astrophysics.

See also edit

External links edit

{{Principles of radiation astronomy}}