Re: This Week's Finds in Mathematical Physics (Week 238)
- From: Kwok Man Hui <kmhui@xxxxxxxxxxxxxxx>
- Date: Thu, 24 Aug 2006 08:07:20 +0000 (UTC)
On Thu, 17 Aug 2006, John Baez wrote:
Markevitch and company have been studying the "Bullet Cluster", a
a bunch of galaxies that has a small bullet-shaped subcluster zipping
away from the center at 4,500 kilometers per second.
It seems that one of the rapidly moving galaxies in this subcluster
has hit a bystander galaxy - I'm not sure, but a high-speed collision
of galaxies occurred.
In fact, the whole subcluster hit another subcluster!
So, the picture is a picture of colliding bunches of galaxies.
The individual galaxies in these bunches mainly shoot right past
each other - but the intergalactic gas in one bunch is hitting
the gas in the other, and getting so hot it emits X-rays.
So, dark matter is seeming more and more real. In fact, last year
folks found evidence for "ghost galaxies" made mainly of dark matter
and cold hydrogen, with very few stars:
6) PPARC, New evidence for a dark matter galaxy,
http://www.interactions.org/cms/?pid=1023641
Apparently the consensus is now that this ghost, VIRGOHI 21,
is hydrogen stripped off from a galaxy by the "wind" it felt
as it fell into the Virgo Cluster. This effect is called
"ram pressure stripping" - the gas of a galaxy can be stripped
off if the galaxy is moving rapidly through a cluster, due
to interaction with the gas in the cluster.
Along with your above comment on "ram pressure stripping",
I would like to talk about an old This Week's Finds, Week 224, about a mono knotted jet from a hypothesized supermassive blackhole in M87 galaxy.
The three pictures from NASA do not show two knotty jets. There is only one jet revealed. I have reviewed several times that the Chandra X-ray telescope picture has shown that there is dim blue light around the brightest center spot. So there are matters or gases around the hypothesized supermassive blackhole. Therefore, there should have another jet (synchrotron radiation) from the acretion disk of the blackhole and that jet should x-ray the inter-galaxtic matters/gases on the other side of the acretion disk as well. However, none is seen.
Would it be possible that there was a high speed small dense dark matter (High speed ,dense and small are required so that it didn't cause a prolonged microlensing effect that can be observable nowaday.) "ram pressure stripping" some tiny galaxies and brought those gases to the current scene? And the small dense dark matter finally hit the center of the M87 galaxy and formed a blackhole (if there is a blackhole)? Look at the Chandra x-ray picture, and notice the blurryness and a very bright spot near the jet tail. Do they look like the remaining part of the "bullet cluster"?
.
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