How does the Milky Way renew its star-forming gas?

There's only about a 1 billion solar masses of gas reservoirs inside the
Milky Way's disk. If it forms one solar mass of stars every year, then
there's only a billion years of star formation left in it. So it must be
getting its gas replenished from outside, but where? Apparently,
according to this study, it's mostly coming from intergalactic gas
that's at wavelengths that are hard to detect. It's gas that is not in
the hot X-ray range, but in the far-UV range, i.e. "warm" gas. This
stuff is so hard to detect that we don't even know how much of it there
is outside. It may even contribute significantly to the missing Dark
Matter count.

Yousuf Khan

Quote:
"This new simulation shows that the mystery of the Milky Way’s gas
supply may not be so mysterious after all: it is extremely difficult to
detect warm ~105 K gas. In the future we may be able to directly detect
this gas using sensitive observations of far ultraviolet emission lines
of Oxygen and Carbon but these observations must be done from space and
probably require a telescope with a much larger mirror than Hubble’s. We
may have a better chance of detecting this gas today with the Cosmic
Origins Spectrograph on HST by finding a sightline toward a bright
background source that shows absorption in the same FUV emission lines.
Unfortunately, this may prove to be difficult: the authors estimate that
the warm infalling gas only covers 20% of the sky implying that finding
a sightline for studies of this gas may be difficult."

http://astrobites.com/2012/05/19/how...y-get-its-gas/

On 5/19/12 9:23 AM, Yousuf Khan wrote:
There's only about a 1 billion solar masses of gas reservoirs inside the
Milky Way's disk. If it forms one solar mass of stars every year, then
there's only a billion years of star formation left in it. So it must be
getting its gas replenished from outside, but where? Apparently,
according to this study, it's mostly coming from intergalactic gas
that's at wavelengths that are hard to detect. It's gas that is not in
the hot X-ray range, but in the far-UV range, i.e. "warm" gas. This
stuff is so hard to detect that we don't even know how much of it there
is outside. It may even contribute significantly to the missing Dark
Matter count.

Yousuf Khan

Quote:
"This new simulation shows that the mystery of the Milky Way’s gas
supply may not be so mysterious after all: it is extremely difficult to
detect warm ~105 K gas. In the future we may be able to directly detect
this gas using sensitive observations of far ultraviolet emission lines
of Oxygen and Carbon but these observations must be done from space and
probably require a telescope with a much larger mirror than Hubble’s. We
may have a better chance of detecting this gas today with the Cosmic
Origins Spectrograph on HST by finding a sightline toward a bright
background source that shows absorption in the same FUV emission lines.
Unfortunately, this may prove to be difficult: the authors estimate that
the warm infalling gas only covers 20% of the sky implying that finding
a sightline for studies of this gas may be difficult."

http://astrobites.com/2012/05/19/how...y-get-its-gas/

smiling