Tuesday, December 8, 2015

Updates on Warm Dark Matter & What's Up with the Lyman Alpha Forest

A couple of quick updates followed by a discussion of the most recent M. Viel paper regarding Lyman Alpha Forest and limits on Warm Dark Matter.

Update#1: Jeltema and Profumo find no evidence for a 3.5 keV line in the Draco spheroidal galaxy. This is yet again another paper that finds no evidence for this 3.5 keV line when looking at dwarf galaxies.  The source of this 3.5 keV line may be unique to elliptical galaxies and likely has nothing to do with dark matter.

Update#2: (Related to LHC) Both the Atlas and CMS detectors recently published data from RunII at 13 TeV and report no evidence for resonances (that would produce di-jets) with mass energies up to ~6 TeV. In other words, cold dark matter and supersymmetry are running out of places to hide.

Update#3: Baur et al. (including M. Viel) put a pre-print of a paper submitted to JCAP titled "Lyman Alpha Forests cool Warm Dark Matter."

The pre-print argues that "Using an unprecedentedly large sample of medium resolution QSO spectra from the ninth data release of SDSS, along with a state-of-the-art set of hydrodynamical simulations to model the Lyman-alpha forest in the non-linear regime, we issue the tightest bounds to date on pure dark matter particles: mX > 4.35 keV (95% CL) for early decoupled thermal relics such as a hypothetical gravitino, and its corresponding bound for a non-resonantly produced right-handed neutrino ms > 31.7 keV (95% CL)."

However, I think that we need to be very skeptical of this work. Here are some of my issues with the manuscript as well as many of the other Lyman Alpha Forest manuscripts out there.