Unidentified emission line in Galaxy Clusters

In summary, a paper was published in The Astrophysical Journal about the detection of an unidentified emission line in the stacked X-ray spectrum of galaxy clusters. This line was detected in three independent MOS spectra and the PN "all others" spectrum. It is believed to possibly be caused by the decay of a sterile neutrino, a dark matter particle candidate. However, there are uncertainties and anomalies in the data that require further confirmation and investigation. Many articles and blogs have been written about this discovery, generating excitement and discussion.
  • #1
DennisN
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I could not find a thread about this (and I hope I don't start a duplicate one :smile:).
I got a mail from a friend today about this:

Detection of An Unidentified Emission Line in the Stacked X-ray spectrum of Galaxy Clusters
Esra Bulbul, Maxim Markevitch, Adam Foster, Randall K. Smith, Michael Loewenstein, Scott W. Randall
A paper was published in the July 1st issue of The Astrophysical Journal.
Arxiv link: http://arxiv.org/abs/1402.2301
(Submitted on 10 Feb 2014 (v1), last revised 9 Jun 2014)

Abstract:
We detect a weak unidentified emission line at E=(3.55-3.57)+/-0.03 keV in a stacked XMM spectrum of 73 galaxy clusters spanning a redshift range 0.01-0.35. MOS and PN observations independently show the presence of the line at consistent energies. When the full sample is divided into three subsamples (Perseus, Centaurus+Ophiuchus+Coma, and all others), the line is significantly detected in all three independent MOS spectra and the PN "all others" spectrum. It is also detected in the Chandra spectra of Perseus with the flux consistent with XMM (though it is not seen in Virgo). However, it is very weak and located within 50-110eV of several known faint lines, and so is subject to significant modeling uncertainties. On the origin of this line, we argue that there should be no atomic transitions in thermal plasma at this energy. An intriguing possibility is the decay of sterile neutrino, a long-sought dark matter particle candidate. Assuming that all dark matter is in sterile neutrinos with m_s=2E=7.1 keV, our detection in the full sample corresponds to a neutrino decay mixing angle sin^2(2theta)=7e-11, below the previous upper limits. However, based on the cluster masses and distances, the line in Perseus is much brighter than expected in this model. This appears to be because of an anomalously bright line at E=3.62 keV in Perseus, possibly an Ar XVII dielectronic recombination line, although its flux would be 30 times the expected value and physically difficult to understand. In principle, such an anomaly might explain our line detection in other subsamples as well, though it would stretch the line energy uncertainties. Another alternative is the above anomaly in the Ar line combined with the nearby 3.51 keV K line also exceeding expectation by factor 10-20. Confirmation with Chandra and Suzaku, and eventually Astro-H, are required to determine the nature of this new line.(ABRIDGED)

Bonus material:
Article 1: Mystery in the Perseus Cluster (NASA article)
Article 2: Perseus Cluster: Mysterious X-ray Signal Intrigues Astronomers (Chandra article)
Article 3: Mysterious signal from the center of the Perseus Cluster unexplained by known physics (The Watchers)
Blogs: Links to some blogs that have written about it.

Just wanted to let the forum readers know about it. It got me a little excited...:-p
 
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  • #2
DennisN said:
Just wanted to let the forum readers know about it. It got me a little excited...:-p

Thanks for sharing! What part are you most excited about?
 
  • #4
Greg Bernhardt said:
Thanks for sharing! What part are you most excited about?

This thing :smile::
From abstract of paper said:
On the origin of this line, we argue that there should be no atomic transitions in thermal plasma at this energy.
But I'm not even remotely qualified to say very much about it, haha!

Chronos said:
Interesting new papers do not escape notice here very often, or long: https://www.physicsforums.com/showthread.php?t=739043&highlight=dark+matter+detection
Excellent! :thumbs: I had a feeling it ought to have appeared on the forum :smile:. I'll make a new post in that very thread, and request for this thread to be closed.

EDIT: I've added the info in the thread by Chronos here now instead.
 
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  • #5
Thread closed at the request of the OP. Any responses to the topic can be made in the threads linked in the posts above.
 

Related to Unidentified emission line in Galaxy Clusters

1. What is an unidentified emission line in galaxy clusters?

An unidentified emission line in galaxy clusters refers to a spectral line that appears in the emission spectra of a galaxy cluster, but its origin is unknown. This line does not correspond to any known element or molecule, and its presence suggests the presence of a new type of matter or physical process within the cluster.

2. How do scientists detect unidentified emission lines in galaxy clusters?

Scientists use spectroscopy, a technique that breaks down the light emitted by an object into its component wavelengths, to detect unidentified emission lines in galaxy clusters. By analyzing the spectra, scientists can identify unusual or unexpected spectral lines that do not match any known elements or molecules.

3. What could be the possible sources of unidentified emission lines in galaxy clusters?

There are several potential sources of unidentified emission lines in galaxy clusters. These could include exotic particles such as dark matter, new types of atoms or molecules, or unknown physical processes that are occurring within the cluster.

4. Why are unidentified emission lines in galaxy clusters important for scientific research?

Unidentified emission lines in galaxy clusters are important because they provide clues about the composition and behavior of these massive objects. They can also help scientists better understand the nature of dark matter and other mysterious phenomena in the universe.

5. What is being done to further investigate and understand unidentified emission lines in galaxy clusters?

Scientists are conducting further observations and experiments to try to identify the sources of these mysterious emission lines. They are also using computer simulations and theoretical models to better understand the physical processes that could produce these lines. Collaboration between different fields of science, such as astrophysics and particle physics, is also helping advance our understanding of unidentified emission lines in galaxy clusters.

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