A Dark Secret in Virgo
This week’s OOTW features my OOTD ‘A Dark Secret in Virgo‘ posted on the 11th of December 2010.
On the 17th of March 1781, Pierre Méchain discovered this beautiful galaxy. NGC4254 lurks 50 million light years away in the constellation Coma Berenices. It’s a disturbed spiral, with its right arm jutting out further than the other. So what’s caused this? Let’s zoom out…
There’s nothing to see that could have caused the disruption, right? Well, let’s zoom into this patch of sky in Coma Berenices’ next door neighbour, Virgo:
Is it a black hole? No. Is it a gigantic cloaked alien ship that tugs galaxies?! Nope. It is in fact VIRGOHI21; a HI region 50 million light years away that was first detected by the Lovell telescope. A HI region is a mass of neutral hydrogen, and in this case it has hardly any or no stars. But there’s something more to this object than meets the eye…
This is a screenshot of an animation (my attempts at posting the animation here failed!) which shows a map of VIRGOHI21. According to this website here the larger brighter mass is NGC 4254, and you can see the cloud is cascading down from the disturbed spiral arm in a stream of neutral hydrogen to the centre of the image. Astronomers have calculated that the total mass of this HI region is 2×10^8 Mʘ (solar masses), but the velocity and spin of this object indicates that there is more mass than we can detect and so the object actually has a mass of 10^11 Mʘ! So where does the rest of the mass come from…?
Dark matter! It is currently thought that VIRGOHI21 is a dark galaxy, which is a starless galaxy made up of mostly dark matter with little else apart from dust and hydrogen. This dark galaxy is interacting with NGC 4254 like any other normal galaxy would!
VIRGOHI21 is currently the best dark galaxy candidate out there, but others include HE0450-2958 which is a quasar that appears to be galaxy-less! Usually quasars have a host galaxy, but this one doesn’t appear to have one that we can see, so it has been proposed that the Quasar is actually part of a dark galaxy.
A survey called AGES uses the Arecibo observatory to find HI regions that are in connection with dark galaxies: http://www.naic.edu/~ages/
2 responses to “A Dark Secret in Virgo”
Trackbacks / Pingbacks
- - December 17, 2010
Galaxy Zoo 
If HE0450-2958 was a quasar that appeared to be galaxy-less and we knew that out of the center of some quasars hot and fast jets were ejected via the magnetic poles into diametrically opposed directions, so that it had been actually proposed that the quasar was actually part of a dark galaxy, mostly consisting of super-WIMPs or something like that, then we could assume that Dark Matter could also collapse into black holes. However, if there is one chance in the distant future to detect the particles of which Dark Matter might consist of, we could find out whether visible matter in supernovae and Dark Matter in “invisible stars” could collapse in a similar way. Then we should ask the following question: if super-WIMPs are so slowly to interact and react with similar particles — unlike visible matter — how could these “invisible stars” or “particle clusters” collapse into such Dark Matter black holes? Do Dark Matter clusters and stars (if there are any) burn their reserves like stars consisting of visible matter? If not how do they collapse — only by an enormous gravitational pull exceeding by far that of visible matter? Are super-WIMPs “heavier” than sub-atmoic and atomic particles of visible matter? If the lack of jets of HE0450-2958 is due to a currently inactive black hole then we could find other questions to be answered. Are quasars being part of a dark galaxy working in the same way like in visible host galaxies? Maybe there exist by far more quasars of dark galaxies than of visible galaxies — provided that the ratio of Dark Matter 23% to 0.5% of visible stars is also true for the ratio of dark and visible galaxies. If this is true then we could find a plausible answer why the first supermassive black holes already appeared shortly after the Dark Age at least 13 billion to 13.4 billion years ago — and if this is the case, then super-WIMPs (unlike in Spektrum der Wissenschaft in December 2010) are not slow to react but they react quite fast in an unknown chemical and physical way. This we must find out. There is at least one tangible result: gravitation is in my eyes the most important maker of natural laws in our universe, however, like matter has its counterparts in anti-matter, gravitation must have a counterpart, too. Is that the Dark Energy? Maybe the Dark Energy hampers super-WIMPs to react as fast as visible matter — and maybe visible matter is only the visible, hotter part and more active part of Dark Matter.
At the end I have one question that was raised by one of my geography students in fall 2009 — a highly-gifted student of a sixth grade/class: If our Milky Way is a cannibal and devours matter of smaller neighboring galaxies and even tears apart the Sagittarius dwarf galaxy could our universe be a cannibal as well, sucking Dark Matter and visible matter from other universes (maybe via black holes or by the expanding force of Dark Energy from other (smaller or larger, younger or older) universes as well? Could Dark Energy be in this case just the expanding force of a universe which simply needs more space to fill with its matter/Dark Matter stolen from other universes? In this case our universe would be like a leech. What happens if the abdomen of the leech is filled with blood and our universe is saturated? The name of this student is Simon Bettinger (in 2010 12 years old).
I am looking forward to your reply.
Sincerely,
Yours,
Matthias Schlicht