[phas-dept] news on dark matter

[Bao-An Li]

To know more about this, please come to the colloquium tomorrow
Oct. 8, Thursdays, 4-5pm in Science 127 (coffee and cookies served at 3:50pm)
All students currently enrolled in Physics 401 and 501 are required to attend all colloquia
Galactic searches for dark matter
Prof. Louis Strigari, Texas A&M University

[X]Dr. Louis Strigari received his Ph.D from The Ohio State University in 2005. He was a Hubble Fellow before joining Texas A&M University.Dark matter, which is deduced through the motions of stars and gas in galaxies, and large scale observations of gravitational lensing and of the cosmic microwave background, is a well-established aspect of cosmological theory. Though its precise nature is unknown, it has become clear its existence points directly to new physics, likely in the form of an undiscovered elementary particle that is connected to a theoretical model such as supersymmetry. Dr. Strigari’s research involves understanding astrophysical aspects of dark matter, and connecting these observations to particle dark matter theories. He works to understand data from high energy astrophysics experiments and from direct dark matter detection experiments. He utilizes numerical simulations and numerical algorithms to model data from dark matter-dominated galaxies.

Abstract:
For nearly a century, more mass has been measured in all types of galaxies than is contained in the visible matter. Through a variety of observations, it has become clear that the dark matter in galaxies is not comprised of known astronomical objects or baryonic matter, and that its identification is certain to reveal a profound connection between astrophysics, cosmology, and fundamental physics. In this talk, I discuss the status of searches for particle dark matter using a variety of different experimental techniques. I conclude by highlighting how in the next several years we will either confirm the leading theoretical model for dark matter, or there will be a paradigm shift in our view of it.

 From: phas-dept-bounces at tamuc.edu [phas-dept-bounces at tamuc.edu] on behalf of Carlos Bertulani [Carlos.Bertulani at tamuc.edu]
Sent: Wednesday, October 07, 2015 11:36 AM
To: Physics & Astronomy Department
Subject: [phas-dept] news on dark matter

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.



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.




cheers nick

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