[phas-dept] news on dark matter

[Carlos Bertulani]

I got this email message below from Prof. Nicholas Suntzeff (College Station). really exciting news about dark matter.

Carlos

From: nsuntzeff <nsuntzeff at tamu.edu<mailto:nsuntzeff at tamu.edu>>
Date: Wed, 7 Oct 2015 00:24:15 -0500
To: <faculty-talk at physics.tamu.edu<mailto:faculty-talk at physics.tamu.edu>>
Cc: "Astrophysics at TAMU" <astro at listserv.tamu.edu<mailto:astro at listserv.tamu.edu>>
Subject: [Faculty-talk] Interacting dark matter

Dear All,

The European Southern Observatory has released some photos and analysis that are quite puzzling. See:

http://www.eso.org/public/images/eso1514a/

What they have found is that through gravitational lensing, they have mapped out the dark matter content around four interacting galaxies buried deep in the core of a cluster of galaxies. What is strange is that there is one galaxy where the dark matter appears to have lagged behind the galaxy. This seems to imply that dark matter is interacting in a non-gravitational way, and perhaps is self-interacting.

This is not like the Bullet Cluster where two galaxies passed through each other, and the interaction separated the gas from the stars/dark matter. Here there is no gas and as the galaxies collide, both the stars and the dark matter will pass through each other. Gravity will slow the components as they pass through each other due to gravitational friction, but the separation of the dark matter and the stars was not expected as seen in the image.

The interpretation is not iron clad at this point, but it is very intriguing.

The picture of the cluster in the article above is also intriguing. I attach the HST image of the cluster. You can see the four elliptical galaxies enveloped in a much larger luminous halo, which is not uncommon in very rich clusters. But if you look closely into the haze, you can see four images of a single galaxy that looks like a blue loop with a dot in the center. It is this multiply imaged galaxy, along with some other arcs that allow such a reconstruction of the dark matter distribution.

[cid:3FA68C7A-25E5-4A07-8779-50567890EA8D]


In this image you can see the derived contours of the dark matter (in dark blue lines). The galaxy to the 10 o’clock position of the quartet has the dark matter contours clearly not centered on the galaxy, which they are interpreting as perhaps due to self interaction of the dark matter. The other three galaxies do not have enough contrast from the lensing to detect such an offset.

[cid:A9E912BC-2280-4A0C-A5E8-49A9C0544DDE]



cheers nick

_______________________________________________ Faculty-talk mailing list Faculty-talk at physics.tamu.edu<mailto:Faculty-talk at physics.tamu.edu> http://mailman.physics.tamu.edu/cgi-bin/mailman/listinfo/faculty-talk
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.tamuc.edu/pipermail/phas-dept/attachments/20151007/c7c2a5b6/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: PastedGraphic-1.tiff
Type: image/tiff
Size: 1157836 bytes
Desc: PastedGraphic-1.tiff
URL: <http://mailman.tamuc.edu/pipermail/phas-dept/attachments/20151007/c7c2a5b6/attachment-0002.tiff>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: PastedGraphic-2.tiff
Type: image/tiff
Size: 2903156 bytes
Desc: PastedGraphic-2.tiff
URL: <http://mailman.tamuc.edu/pipermail/phas-dept/attachments/20151007/c7c2a5b6/attachment-0003.tiff>