# Synopsis: Sterile Neutrino as Dark Matter Candidate

A dark matter particle in the form of a noninteracting neutrino could explain the recent detection of an x-ray emission line from galaxy clusters.

A hypothetical neutrino that does not interact through the weak force could be the source of a recently detected x-ray emission line coming from galaxy clusters. However, previous models using this so-called “sterile” neutrino as a form of dark matter were not able to satisfy constraints from cosmological observations. Now, writing in Physical Review Letters, Kevork Abazajian of the University of California, Irvine, shows that a sterile neutrino with a mass of $7$ kilo-electron-volts (keV) could be a viable dark matter candidate that both explains the new x-ray data and solves some long-standing problems in galaxy structure formation.

Cosmologists have long considered neutrinos as possible dark matter particles. However, because of their small mass (less than about $1$ eV), conventional neutrinos are too fast, or “hot,” to form the dense dark matter structures needed to hold galaxies and galaxy clusters together. By contrast, sterile neutrinos, which result from certain neutrino theories, can have larger masses and could have been naturally produced in the big bang by neutrino flavor mixing.

The problem has been that sterile neutrinos should decay, producing an x-ray signal that no one has observed—until maybe now. Earlier in 2014, an analysis of galaxy cluster data revealed an x-ray emission line, which is consistent with the decay of a $7$-keV sterile neutrino. Normally, dark matter with this mass would be too “warm” to match galaxy data. However, Abazajian showed that the sterile neutrinos could have a “cooler” momentum distribution if they were produced through resonantly enhanced neutrino flavor mixing (the MSW effect). When Abazajian plugged this neutrino into a cosmological model, he found it could explain both the small number of Milky Way satellite galaxies and their central densities, which have eluded the currently favored cold dark matter model. – Michael Schirber

More Features »

### Announcements

More Announcements »

Optics

## Next Synopsis

Materials Science

## Related Articles

Astrophysics

### Focus: Hard and Soft Bounces Explain Asteroid’s Surface Structure

Experiments and computer simulations show that the segregation of small and large rocks on an asteroid’s surface can arise from the way particles hitting the surface collide with the rocks already present. Read More »

Particles and Fields

### Viewpoint: Spinning Gluons in the Proton

Computer simulations indicate that about 50% of the proton’s spin comes from the spin of the gluons that bind its quark constituents. Read More »

Astrophysics

### Synopsis: Neutrino Flashes from Exploding Stars

Calculations indicate that neutrino emission from a supernova could be detected on Earth, possibly revealing how the star explodes. Read More »